Many taxa show substantial differences in lifespan between the sexes: however, these differences are not always in the same direction

The sex with the reduced sex chromosome dies earlier: a comparison across the tree of life. Zoe A. Xirocostas, Susan E. Everingham and Angela T. Moles. Biology Letters, March 4 2020. https://doi.org/10.1098/rsbl.2019.0867

Abstract: Many taxa show substantial differences in lifespan between the sexes. However, these differences are not always in the same direction. In mammals, females tend to live longer than males, while in birds, males tend to live longer than females. One possible explanation for these differences in lifespan is the unguarded X hypothesis, which suggests that the reduced or absent chromosome in the heterogametic sex (e.g. the Y chromosome in mammals and the W chromosome in birds) exposes recessive deleterious mutations on the other sex chromosome. While the unguarded X hypothesis is intuitively appealing, it had never been subject to a broad test. We compiled male and female longevity data for 229 species spanning 99 families, 38 orders and eight classes across the tree of life. Consistent with the unguarded X hypothesis, a meta-analysis showed that the homogametic sex, on average, lives 17.6% longer than the heterogametic sex. Surprisingly, we found substantial differences in lifespan dimorphism between female heterogametic species (in which the homogametic sex lives 7.1% longer) and male heterogametic species (in which the homogametic sex lives 20.9% longer). Our findings demonstrate the importance of considering chromosome morphology in addition to sexual selection and environment as potential drivers of sexual dimorphism, and advance our fundamental understanding of the mechanisms that shape an organism's lifespan.

4. Discussion

Our study provides evidence that, across multiple taxa, the heterogametic sex tends to have a considerably shorter lifespan than the homogametic sex. That is, an organism's chromosome morphology seems to have a substantial role in shaping this key life-history trait. The 17.6% difference between the lifespans of homogametic and heterogametic sexes revealed here is substantial enough to have major ecological and evolutionary implications. However, heterogametic sex chromosomes include everything from a complete absence of the second sex chromosome (X0 or Z0), to a highly reduced second sex chromosome (e.g. XY in humans), to X and Y or Z and W chromosomes of nearly equal length [5,32,33]. As not all heterogametic species have a degraded sex chromosome, our study likely represents a conservative test of the unguarded X hypothesis. A future direction will be to formally test the hypothesis that the difference in lifespan between sexes is proportional to the proportional difference in chromosome length between sexes. That is, to test the idea that species in which the second chromosome is absent or extremely reduced have a greater reduction in the lifespan of the heterogametic sex than do taxa in which the difference between sex chromosomes is relatively small. Ideally, this question should be addressed using a diverse range of taxa, both for generality, and to include species with as many different chromosome configurations, life histories and mating systems as possible. Another interesting direction for future research would be to begin to quantify the relative contributions of factors such as chromosome morphology, sexual selection, parental investment and exposure to predators.

Our second major finding was that when males are the heterogametic sex, they die 20.9% earlier than their female counterparts, but when females are the heterogametic sex, they die only 7.1% earlier than their male counterparts. Three possible explanations for this surprising trend include: (1) the degree of degradation of the Y chromosome, (2) telomere dynamics, and (3) side effects of sexual selection.

(1)	It is possible that the Y chromosome in male heterogametic species might tend to be more degraded than the W chromosome in female heterogametic species, potentially leading to a difference in heterogametic lifespan between XY and ZW systems. We know that many mammals (including humans) have highly reduced Y chromosomes [33–35]. There is also evidence that the relative length of the W and Z chromosomes can vary substantially even within clades (e.g. birds, snakes; [6,36–39]). However, a comparative analysis of the degradation of chromosomes across the tree of life has not yet been performed.
(2)	Telomeres are sections of non-coding DNA at the ends of chromosomes that protect coding DNA from deterioration during cell replication and other cellular processes [40,41]. Cell replication damages telomeres and studies suggest that the loss of telomere length over time causes the progression of ageing and shortening of lifespan [42]. However, oestrogen stimulates a promoter of the telomerase enzyme [43], which heals damaged telomeres by adding telomeric base pairs to its ends and indirectly activates other DNA repairing pathways [40]. Although we do not know whether oestrogen is important in all of our study species, it is possible that the effect of oestrogen on telomerase activation could help to explain the smaller decrease in lifespan when females are the heterogametic sex.
(3)	In many cases, males experience more intense sexual competition than females, as they are more reproductively efficient and so take more risks when pursuing a mating opportunity (e.g. males fighting for access to females or to establish their territory) [44,45]. Usually, females are not as efficient at reproducing, contribute more to their offspring than fathers, and so are predicted to engage in lower-risk behaviours [44–46]. Higher mortality in males owing to side effects of sexual selection, in combination with the effect of sex chromosomes on longevity, could also explain why there is a smaller lifespan difference between ZW females and ZZ males in comparison with XY males and XX females [11,15,44].

Understanding the mechanisms underpinning the substantial difference in lifespan dimorphism in male versus female heterogametic species is an important direction for future research, as this may improve our understanding of the factors that affect ageing. There is a multibillion-dollar industry in extending human lifespan [47], however, there is a crucial knowledge gap and we have much to learn about the basic biology underpinning longevity and the drivers of lifespan differences across sexes and species. Here, we have provided the first evidence that the heterogametic sex does, on average, die earlier than its homogametic counterpart across a range of taxa. We also found that lifespan dimorphism between the sexes is greater in male heterogametic species in comparison with female heterogametic species. These findings are a crucial step in uncovering the underlying mechanisms affecting longevity, which could point to pathways for extending life. We can only hope that more answers are found in our lifetime.

The human physiology of well-being: A systematic review on the association between neurotransmitters, hormones, inflammatory markers, the microbiome and well-being

The human physiology of well-being: A systematic review on the association between neurotransmitters, hormones, inflammatory markers, the microbiome and well-being. Lianne P.de Vries et al. Neuroscience & Biobehavioral Reviews, June 11 2022, 104733. https://doi.org/10.1016/j.neubiorev.2022.104733

Highlights

• Higher blood levels of serotonin could be related to higher well-being.

• Faster decrease of cortisol levels over the day is associated with higher well-being.

• The levels of different inflammatory markers are negatively related to well-being.

• An association between the microbiome composition and well-being is suggested.

• More research to the physiological factors underlying well-being is needed.

Abstract

To understand the pathways through which well-being contributes to health, we performed a systematic review according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines on the association between well-being and physiological markers in four categories, neurotransmitters, hormones, inflammatory markers, and microbiome.

We identified 91 studies. Neurotransmitter studies (knumber of studies=9) reported only a possible positive association between serotonin and well-being. For the hormone studies (k=48), a lower momentary cortisol level was related to higher well-being (meta-analytic r=-.06), and a steeper diurnal slope of cortisol levels. Inflammatory marker studies (k=36) reported negative or non-significant relations with well-being, with meta-analytic estimates of respectively r=-.07 and r=-.05 for C-reactive protein and interleukin-6. Microbiome studies (k=4) reported inconsistent associations between different bacteria abundance and well-being.

The results indicate possible but small roles of serotonin, cortisol, and inflammatory markers in explaining differences in well-being. The inconsistent and limited results for other markers and microbiome require further research. Future directions for a complete picture of the physiological factors underlying well-being are proposed.

Keywords: well-beingphysiologyneurotransmittershormonesinflammatory markersmicrobiome

4. Discussion

To understand observed differences in well-being between people in more detail, and in order to enhance the development of future mental health prevention and intervention strategies, it is essential to identify physiological markers related to well-being. Therefore, the goal of this systematic review was to bring together the available literature on physiological markers related to well-being in four categories, namely neurotransmitters, hormones, inflammatory markers, and the microbiome. The systematic review resulted in respectively 48 and 36 studies on the association of hormones or inflammatory markers and well-being, whereas only 9 and 4 studies examined the relation between neurotransmitters or the microbiome and well-being. We first summarize and discuss the findings per category. Next, we propose directions for future research based on our current results.

4.1. Neurotransmitters

Nine studies investigated the association between levels of different neurotransmitters and well-being, mainly focusing on (nor)epinephrine and serotonin. In contrast to our expectations, we did not find studies that related dopamine levels to well-being and only a few studies related to (nor)epinephrine and serotonin. Levels of epinephrine and norepinephrine were mostly unrelated to measures of psychological well-being and positive affect. Only in a sample of older women (mean age=74), there was a moderate positive correlation between (nor)epinephrine and subscales of Ryff’s psychological well-being scale. More research on the moderating effects of well-being measure, age and sex is needed to confirm these findings.

Serotonin levels were more consistently positively related to the hedonic well-being measure positive affect, but the effect sizes were small. The relation between serotonin and other measures of hedonic well-being, e.g., life satisfaction, or eudaimonic well-being has not been investigated so far. In studies with larger sample sizes the moderation by age and sex should also be investigated.

The results should be interpreted in light of the difficulties of measuring neurotransmitters levels in humans due to their short term effects, low levels in the brain, and their mixture with other molecules (Niyonambaza et al., 2019). Furthermore there is an ongoing discussion whether urine or blood plasma measures of neurotransmitters reflect brain activity (Ailts et al., 2007, Marc et al., 2011). The suggested positive correlation between neurotransmitter levels in the brain and the rest of the body, i.e., urine or blood (Marc et al., 2011) does suggest that the detected association between serotonin in the blood plasma and well-being indicates the involvement of serotonin resulting from brain activity in well-being.

Applying positron emission tomography (PET) and labeling neurotransmitters can help to identify the regional specificity in the brain of neurotransmitters associated with well-being. For example, in the field of anxiety, it has been found that neurotransmission in social anxiety disorder is characterized by an overactive serotonin system in the amygdala, caudate nucleus, putamen, hippocampus and anterior cingulate cortex (Frick et al., 2015). Similarly, PET studies can directly give insight in the association of well-being and functioning of neurotransmitters in specific brain regions.

Furthermore, there is a lot of development in new ways to assess serotonin in different tissues and with new techniques, such as real-time continuous monitoring (Si and Song, 2018, Su et al., 2020). This might enable researchers to assess the level of different neurotransmitters more easily in the future and replicate the possible involvement of serotonin in complex traits like well-being.

4.2. Hormones

The association of different hormones with well-being has been investigated more often compared to the neurotransmitter research, as hormones are currently easier to assess via, for example, saliva samples. Of the 48 hormone studies, 39 studies included one or more measures of cortisol. The meta-analysis on the association between the level of momentary cortisol and well-being resulted in a small negative effect, r=-.06, indicating that lower cortisol levels are related to higher levels of well-being. In addition, although a meta-analysis could not be performed, another relatively consistent finding was the association of a faster decrease of cortisol levels over the day (i.e., steeper slope) with higher well-being. The results of the relation between the cortisol awakening response and total cortisol secretion and well-being were less consistent. However, as reported by Smyth et al. (2015), the timing of cortisol sampling is important. In their study, only when the participants strictly adhered to the sampling protocol, lower cortisol awakening response was associated with higher well-being. Furthermore, as indicated by Booij et al. (2016), large individual differences in the relation between different measures of cortisol and well-being were present in their sample. This makes it difficult, if not impossible, to find consistent associations when averaging the relation within a large sample. In an earlier review, the inconsistency of findings regarding hormones and positive affects is also suggested to be due to the variability in samples, age, measures of well-being and timing (Dockray and Steptoe, 2010). Furthermore, as cortisol is “the stress hormone” and there is a clear negative association between stress and well-being (e.g., Schiffrin et al., 2009), stress might mediate the relation between diurnal cortisol and well-being and controlling for stress is needed in future studies.

Cortisol can be sampled in saliva, urine, or hair and the levels in the different samples reflect different processes. Whereas salivary and urinary cortisol reflect the real-time levels of cortisol, hair cortisol reflects the cortisol exposure over longer periods of time and is related to chronic stress (Russell et al., 2012). Cortisol measured in cortisol and urine versus hair is therefore not directly comparable. We identified two studies using a hair sample of cortisol and only one (Smyth et al., 2016) reported a small negative association with well-being in elderly participants. Research in larger samples is needed to examine the relation of hair cortisol (i.e., long-term cortisol exposure) and well-being.

To summarize, most measures of cortisol were not consistently related to well-being and individual differences could play a large role in the association. However, the small associations between momentary levels of cortisol and the slope of the cortisol decrease over the day and well-being were consistent. This effect was not different for hedonic and eudaimonic well-being. In future research, researchers need to be stricter on the timing of the cortisol sample and avoid variability, e.g., by using tube caps with time recording and strict instructions to the participants. In addition, focusing on the individual patterns instead of the average cortisol response or level across individuals is necessary to understand the relation between cortisol and well-being in more detail.

The association of other hormones with well-being were investigated in only a few studies and most of these studies did not report a (consistent) significant association, limiting the ability to draw conclusions. DHEA-S and testosterone were not related to different measures of well-being in respectively 5 of the 6 studies and 3 of the 4 studies. This might reflect a power issue, as most sample sizes of the discussed studies are small (n<100) or the absence of a detectable association between the levels of these hormones and well-being. More promising is the positive relation between vitamin-D in the blood and well-being. However, since this is based on only two studies, more research is needed to confirm this association.

Whereas oxytocin has mainly been investigated in relation to positive social behaviour, oxytocin is also suggested to play a role in different behaviors and traits related to well-being, such as emotional processing, trust and depressive behaviors (IsHak et al., 2011). However, surprisingly, the direct relation between oxytocin and well-being has only been investigated in a single study (Barraza et al., 2013). In a small sample (noxytocin=21) of older adults (Mage=80) no association could be reported. Future direct and powerful studies should shed more light on the hypothesized association between well-being and oxytocin.

Finally, most studies on the different hormone levels included relatively older samples (average age: 53.1, and in 6 of the 14 studies the average age is above 65). Since hormone production and levels are affected by age (Sternbach, 1998, Van Cauter et al., 1996), more research is needed to study the effects of age on the association between hormones and well-being in age diverse samples.

4.3. Inflammatory markers

The results of the 36 studies on the inflammatory markers and well-being showed more consistent results compared to the previous categories. CRP was negatively associated with well-being in 14 of the 26 studies and IL-6 was negatively associated with well-being in 11 of the 25 studies, whereas the other studies did not find a significant effect. Additionally, both CRP (r=-.07) and IL-6 (r=-.05) showed small but significant negative relations with well-being in a meta-analysis. Based on the available studies, the well-being measure was not a significant moderator, suggesting that the inflammatory markers have an influence on overall well-being and not on specific aspects of hedonic or eudaimonic well-being.

Besides CRP and IL-6, fibrinogen was negatively related to well-being in three of the seven studies, and other inflammatory markers such as other interleukins or white blood cell count were either negatively related with well-being or non-significantly. Based on these results, a consistent pattern of negative associations between different inflammatory markers and well-being emerges. Lower levels of baseline inflammatory markers, i.e., reflecting less activation of the immune system, is linked to higher well-being. The non-significant findings can either be due to weaker designs or smaller samples, leading to lower power.

Similar to the hormone studies, the reviewed inflammatory marker studies included relatively older samples. The average age of the samples is 52.6 (SD=13.7) and in 17 of the 36 studies the average age is above 50, while only two studies the average age is below 30 years. As some studies suggested moderation by age (e.g., Fancourt and Steptoe, 2020), more research is needed into the effects of age on the association between inflammation and well-being in younger and age diverse samples.

A next step in the research on inflammation and well-being is the direction of effect. The direction of effect between inflammation and mental ill-being, i.e., depression, appears to be bidirectional. Patients with inflammatory diseases have a higher likelihood to develop major depressive disorder and often individuals with major depression show increased inflammatory markers, and the levels decrease with the recovery from depression (e.g., Amodeo et al., 2018; Dahl et al., 2014). As well-being and mental ill-being are related but have independent effects on health and other outcomes, the direction of effect between inflammation and well-being should be investigated. Some longitudinal studies in this review showed significant associations between inflammatory markers and well-being a few years later, indicating a possible causal effect from inflammation to well-being.

4.4. Microbiome

Lastly, the composition and diversity of the gut microbiome in relation to well-being is a relatively new and fast developing research field. We could only identify four studies that related the gut microbiome diversity or composition to well-being. All studies reported significant results with the abundance of different bacteria or the diversity of the microbiome associated with higher hedonic well-being, i.e., positive affect or quality of life, indicating that it is likely that the microbiome plays a role in well-being. However, more research is needed to be confident about the specific associations between the microbiome composition and well-being, because one study only included 3 participants, different effects of different bacteria have been studied, and there might be a publication bias in that only studies with significant effects are published in this upcoming field.

Microbiome research is further complicated by the possible effects of variation in dietary habits and geography on the composition of the gut microbiota. Ideally, when investigating the microbiome, participants should be in a stable environment, keep a constant diet and living habit, and maintain a certain activity level. As this can be difficult in daily life, Li et al. (2016) minimized the possible confounding by other factors by investigating three participants that stayed 105 days in a closed human life support system with minimal interference, i.e., a laboratory that simulates a lunar-like environment. This study gave the first insights in the unconfounded relation between the gut microbiome and well-being. In future studies outside such a system, the possible confounding by diet, environment and activity should be taken into account.

Another point of discussion is the current sampling methods for gut microbiome. Tang et al. (2020) reviewed the methods and concluded that more precise sampling methods for the composition and diversity of the gut microbiome are needed. Current measures from fecal samples (and other non-invasive methods) are just a proxy for the composition of the gut microbiome. More precise sampling methods are needed to increase the reliability of the microbiome research and to replicate findings.

4.5. Future directions

In different categories consistent relationships between physiological markers and well-being (e.g., the hormone cortisol, and inflammatory markers CRP and IL-6) were reported. With respect to these effects, further research should be conducted to investigate the direction of the effect or possible moderators or confounders on the effect, as suggested above. In other categories, such as neurotransmitters and the microbiome, additional research is needed to get a complete picture of the role of these physiological markers in relation to well-being. Besides further research into the association of physiological markers related to well-being in the single categories, promising fields for future research include the integration or combination of multiple physiological categories in relation to well-being, the direction of causality, and innovative ways to measure and analyze physiological data.

4.5.1. Integration

A first observation based on the reviewed studies is that the findings of the different studies are diverse and not connected. Most studies investigated the relation between one physiological marker and well-being. Similar to the criticized candidate gene literature (i.e., investigating the association of a single or a few candidate genes with well-being, depression or other genetically complex phenotypes) in which results are mixed and do not seem to replicate (e.g., Border et al., 2019; Johnson et al., 2017; van de Weijer, in press), the pick-and-choose strategy for physiological markers might have led to similar inconsistent results. Where the genome-wide association approach has been introduced to systematically search for genetic variants for complex traits, a similar data-driven approach should be used for future research into the physiology of well-being. Combining multiple physiological markers across the different categories, aka an multi-omics approach, could result in a more complete picture of the physiology underlying well-being.

Combining multiple physiological markers across the different categories could result in a more complete picture of the physiology underlying well-being. An example of combining data is multi-omics approaches, that combine and integrate multiple types of omics data, such as genomics, proteomics, transcriptomics, epigenomics, metabolomics, and microbiomics (Hasin et al., 2017). All the different processes influence each other and by combining these data, researchers can get a broader picture and a more comprehensive insight in the physiological markers and human biology underlying traits or diseases. To learn more about multi-omics, Wörheide et al. (2021) and Subramanian et al. (2020) provide helpful overviews and different applications of this approach within the domain of mental ill-being, e.g., for aggressive behavior and psychiatric disorders, can be found (Hagenbeek et al., 2021, Korologou-Linden et al., 2021).

To understand the physiology underlying well-being, multi-omics approaches can also be applied to the combination of hormones, neurotransmitters, inflammatory markers, and the microbiome. For example, the stress hormone cortisol, and inflammation, the reaction of the immune system, are strongly linked (e.g., Adam et al., 2017; Morey et al., 2015). Furthermore, recent research reported an influence of the gut microbiome on mental health via the level of neurotransmitters (Liu et al., 2020). The gut microbiome can alter the levels of different neurotransmitter and this alteration of neurotransmitters influences mental health. Similarly, an interaction between three categories, namely the gut microbiome, the stress response, including cortisol, and immune system is suggested to play a role in depression, and anxiety (Peirce and Alviña, 2019). As we have shown that cortisol, different immune factors and possibly the microbiome are associated with well-being, investigating these factors at the same time might lead to a clearer picture about the relation between the human physiology and well-being. To conclude, for a complete overview of the physiological markers underlying well-being, combining measures of multiple physiological markers into a large well-being study is needed.

4.5.2. Direction of effect

As we reported consistent associations of (diurnal) cortisol and different inflammatory markers with well-being, a next step is to investigate the direction of the effect between the physiological marker and well-being. Can the association be explained by a causal relationship from the physiological marker to well-being, vice versa, in both directions or is the association explained by another factor? If the direction of causation is known, this can help to design interventions to enhance well-being or prevent poorer mental health. The reported associations in this review are only correlational and it is impossible to determine causality in cross-sectional observational studies. Causality analyses, such as longitudinal (intervention) studies and Mendelian Randomization can enable future researchers to investigate the direction of causality in this field.

Longitudinal studies in which either well-being or the level of physiological factors, such as hormones or neurotransmitters are observed over time, or manipulated (e.g., by triggering their response or substitution) can allow for causal interferences to be made. For example, in the experimental design of Barraza et al. (2013) half of the participants received oxytocin for 10 days and the other half a placebo. The levels of well-being were compared before and after the treatment. There was no effect of the treatment on well-being in both groups. However, if an increase in well-being the oxytocin group, but not the placebo group had been reported, this would be evidence for a causal relation between oxytocin and well-being. Similarly, the other way around, interventions that increase well-being can be used to investigate if well-being has a causal effect on various physiological factors. For example, a meta-analysis across 20 randomized control trials (RCT) reported that mindfulness mediation is associated with immune system processes involved in inflammation, and biological aging, i.e., meditation resulted in a decrease in CRP levels (Black and Slavich, 2016). Similarly, a recent meta-analysis on the effects of meditation interventions on cortisol levels reported that such interventions resulted in reduced cortisol levels, but only when assessed in blood compared to saliva and in people at risk for somatic illnesses (Koncz et al., 2021). As mindfulness and meditation have also been linked to increased well-being, these findings could indicate a causal link between well-being and different physiological factors. Future randomized control studies specific to well-being interventions or physiological manipulations are needed to confirm these hypotheses and investigate the direction of causation.

Another approach to study the direction of causation, that does not need longitudinal data or any intervention, is Mendelian Randomization (MR), which uses genetic variants to test the causal relationships between an exposure variable and outcome. MR relies on the natural, random assortment of genetic variants resulting in a random distribution of genetic variants in a population (Smith and Ebrahim, 2003). In short, if the assumptions are met and a genetic variant is associated both with the exposure (e.g., inflammatory marker levels) and the outcome (e.g., well-being), this would provide supportive evidence for a causal effect of the immune response on well-being. To learn more about Mendelian Randomization, see Gagliano Taliun and Evans, (2021) and Smith and Ebrahim (2003) for an overview and guidelines. Different applications of this approach within the domain of mental ill-being with physiological factors can be found as well (for example (Kappelmann et al., 2021, Perry et al., 2021).

Finally, results of animal studies can indicate possible causal effects of well-being and physiological factors. Although there are limitations in generalizing results from animal studies to human well-being, these results can be the starting point for research in humans and provide clues about the mechanisms and causality. Animal research has been helpful in health-related research areas, but is rare in the well-being field, largely because of the subjective nature of well-being. In the field of depression and stress, animal research on physiological factors has reported different causal mechanisms. For example, in rats, a microbiome transplantation from severely depressed patients to the rats induced depression-like behaviors, like anhedonia and anxiety-like behaviours (Kelly et al., 2016). Similarly, rodents that experienced more induced stress showed higher levels of inflammatory markers (Powell et al., 2013). These results could indicate a possible causal effect between well-being and different physiological factors and future animal research to well-being can be used to investigate causality and confirm these hypotheses.

4.5.3. Innovations and data-driven research

Related to innovations in the methods to measure physiological markers, e.g., real-time continuous monitoring (Si and Song, 2018, Su et al., 2020), there are also rapid developments in the approaches to collect and analyse (big) data. Using the developments in the artificial intelligence and machine learning fields, patterns can be detected in physiological data that we would not predict. These approaches enable us to focus more on data-driven research instead of hypothesis driven research (Scheel et al., 2020). For example, using a data driving approach, and applying machine learning, Poletti et al. (2021) could distinguish between unipolar and bipolar depression based on the plasma levels of 54 cytokines, chemokines and growth factors (i.e., the immune-inflammatory signature) of the participants. For more information about artificial intelligence and machine learning, see overview articles, e.g., Jordan and Mitchell, 2015; Yann LeCun, Yoshua Bengio, 2015). Different applications of this approach within the domain of mental ill-being with physiological factors can be found as well (for example (Poletti et al., 2021, Wardenaar et al., 2021).

4.6. Limitations

The low number of studies in some categories of this systematic review limits our ability to draw more firm conclusions about the association between the physiological factors and well-being and this highlights the need for more studies investigating the physiology of well-being. Furthermore, the low number of studies could indicate a possible publication bias, especially in the newer fields, if studies with non-significant findings are not published.

Another limitation, touched upon briefly in the results of the different categories, is that only a limited number of studies controlled for negative affect and depressive symptoms when investigating physiological factors in relation to well-being. Since well-being and ill-being are related (Baselmans et al., 2018, Okbay et al., 2016), controlling for ill-being when investigating the relation between physiological factors and well-being can help to disentangle the independent associations of physiological factors with well-being and ill-being.

A similar approach of controlling for confounding effects could be interesting for hedonic and eudaimonic well-being measures. Although hedonic and eudaimonic well-being measures are strongly correlated, they also capture slightly different parts of well-being. As proposed by Ryff et al. (2004) hedonic and eudaimonic well-being could have partly different neurobiological and physiological correlates. To learn more about the distinction between hedonic and eudaimonic well-being, future studies should include both measures and when examining the effects of hedonic well-being control for eudaimonic well-being and vice versa.

A quantitative meta-analysis on the association between cortisol levels, two inflammatory markers (CRP and IL-6), and well-being was possible due to a substantial number of homogenous study designs and reported effects. We only included studies that reported bivariate correlations, not including standardized regression coefficients and other effect sizes, since in many regression different covariates are added, leading to biased estimates when including the partial correlations between the markers and well-being. As a result, for the other categories and factors, a meta-analysis was not possible, since the studies were too heterogeneous in study methods, analysis techniques, and reported statistics. Furthermore, even though we performed a detailed literature search according to the PRISMA guidelines, it is possible we missed some papers.

Finally, in all included studies, well-being is measured with self-report measures. While self-report has its limitations, i.e., recall and reporting biases, well-being is conceptually a subjective experience and currently it is not possible to reliably measure well-being objectively.

4.7. Conclusion

[...]

Higher neuroticism was related to lower grip strength ; higher extraversion, openness, & conscientiousness were associated with higher grip strength across most samples

Five-factor model personality traits and grip strength: Meta-analysis of seven studies. Yannick Stephan et al. Journal of Psychosomatic Research, June 11 2022, 110961. https://doi.org/10.1016/j.jpsychores.2022.110961

Abstract

Objective: To examine the association between Five-Factor Model personality traits and grip strength.

Method: Adults aged 16 to 104 years old (N > 40,000) were from the Health and Retirement Study, the Midlife in the United States Study, The English Longitudinal Study of Aging, the National Health and Aging Trends Survey, the United Kingdom Household Longitudinal Study, and the Wisconsin Longitudinal Study graduate and sibling samples. Participants had data on personality traits, demographic factors, grip strength, and mediators such as depressive symptoms, physical activity, body mass index (BMI), and c-reactive protein (CRP).

Results: Across all samples and a meta-analysis, higher neuroticism was related to lower grip strength (meta-analytic estimate: -0.07, 95%CI: −0.075; −0.056). Higher extraversion (0.04, 95%CI: 0.022; 0.060), openness (0.05, 95%CI: 0.032; 0.062), and conscientiousness (0.05, 95%CI: 0.04; 0.065) were associated with higher grip strength across most samples and the meta-analysis. Depressive symptoms were the most consistent mediators between neuroticism and grip strength. Depressive symptoms and physical activity partly mediated the associations with extraversion, openness, and conscientiousness. Lower CRP partly mediated the association with conscientiousness. Sex moderated the associations for extraversion, openness, and conscientiousness, with stronger associations among males. Age moderated the neuroticism association, with stronger associations among younger individuals.

Conclusion: This study provides replicable evidence that personality is related to grip strength and identifies potential moderators and mediators of these associations. Overall, higher neuroticism is a risk factor for low grip strength, whereas high extraversion, openness, and conscientiousness may be protective.

Contrary to Sigmund Freud's suggestion, people who achieve extraordinary careers are not "wrecked by success"

Wrecked by Success? Not to Worry. Harrison J. Kell et al. Perspectives on Psychological Science, June 10, 2022. https://doi.org/10.1177/17456916211055637

Abstract: We examined the wrecked-by-success hypothesis. Initially formalized by Sigmund Freud, this hypothesis has become pervasive throughout the humanities, popular press, and modern scientific literature. The hypothesis implies that truly outstanding occupational success often exacts a heavy toll on psychological, interpersonal, and physical well-being. Study 1 tested this hypothesis in three cohorts of 1,826 high-potential, intellectually gifted individuals. Participants with exceptionally successful careers were compared with those of their gender-equivalent intellectual peers with more typical careers on well-known measures of psychological well-being, flourishing, core self-evaluations, and medical maladies. Family relationships, comfort with aging, and life satisfaction were also assessed. Across all three cohorts, those deemed occupationally outstanding individuals were similar to or healthier than their intellectual peers across these metrics. Study 2 served as a constructive replication of Study 1 but used a different high-potential sample: 496 elite science/technology/engineering/mathematics (STEM) doctoral students identified in 1992 and longitudinally tracked for 25 years. Study 2 replicated the findings from Study 1 in all important respects. Both studies found that exceptionally successful careers were not associated with medical frailty, psychological maladjustment, and compromised interpersonal and family relationships; if anything, overall, people with exceptionally successful careers were medically and psychologically better off.

Keywords: eminence, outstanding careers, physical health, psychological well-being, replication

Cisgender men most like "I am currently single, over past 4 years I have not been in any relationships"; cisgender women/transwomen/transmen/nonbinary most like "I am currently single; over past 4 years I have been in two relationships"

Is the Grass Really Greener? The Influence of Gender Identity and Sexual Orientation on Mate Copying Behaviors. Alyce S. Jarrett & Ryan C. Anderson. The Journal of Sex Research, Jun 9 2022. https://doi.org/10.1080/00224499.2022.2078949

Abstract: Mate copying is a sexual strategy whereby individuals attend to socially available information about their prospective mate. This allows for more accurate decision making in regard to mating. This phenomenon was originally demonstrated among nonhumans, but there is an increasing weight of evidence suggesting that humans also engage in mate copying. Research typically focuses on heterosexual cisgender women, with no previous studies having looked at those identifying outside of the traditional gender binary. The current study aimed to address this gap by examining the impact of gender identity and sexual orientation on the propensity to engage in mate copying. Participants (N = 831) completed an online survey providing desirability ratings for photographs alone (T1) and then rated the same photographs after receiving social information about the relationship status and previous relationship history of the pictured individual (T2). It was found that both gender identity (F(4, 713) = 3.94, ηp2 = .02) and sexual orientation (F(4, 713) = 4.40, ηp2 = .02) influenced an individual’s overall propensity to mate copy, and that desirability patterns for individuals were very different depending on these variables. It was concluded that while mate copying certainly is evident among humans, the phenomenon is extremely nuanced and sensitive.

People lie only to a limited extent to gain certain material advantages, and sometimes they even lie to their own disadvantage to protect their social image

The optics of lying: How pursuing an honest social image shapes dishonest behavior. Mika Guzikevits, Shoham Choshen-Hillel. Current Opinion in Psychology, June 9 2022, 101384. https://doi.org/10.1016/j.copsyc.2022.101384

Highlights

• People lie often, but they do so to a limited extent.

• Limited dishonesty has been explained by concern with a positive self-image.

• People also limit their lying to preserve a positive reputation or social image.

• Both self and social image lead people to limit their dishonesty.

Abstract: People frequently engage in dishonest behavior. Yet, they do so only to a limited extent, often forgoing potential profits. In the past few decades, the dominant psychological account explaining people’s “limited dishonesty” characterized this behavior as driven by a desire to preserve a positive image of the self. Recently, a new account has been put forward, based on social considerations. This social image account claims that limited dishonesty is driven by a desire to be viewed positively by others. Here we review empirical findings from psychology and behavioral economics on the role of social image in dishonest behavior. We conclude by suggesting that both self-image and social image are at play.

Keywords: DishonestbehaviorLyingSocial imageReputation

Traditional creative occupations ('artists' & 'authors') were associated with elevated genetic risk for a range of psychiatric disorders, but similar, or greater elevations were seen for religious, helping and teaching professions

Is an elevated family-genetic risk for major psychiatric disorders specific to creative occupations? Kenneth S. Kendler et al. Psychological Medicine, Jun 8 2022. https://www.cambridge.org/core/journals/psychological-medicine/article/abs/is-an-elevated-familygenetic-risk-for-major-psychiatric-disorders-specific-to-creative-occupations/003E0401E67E8FD52BA96B4A1C6BEDAB

Abstract

Background: Despite a large descriptive literature linking creativity and risk for psychiatric illness, the magnitude and specificity of this relationship remain controversial.

Methods: We examined, in 1 137 354 native Swedes with one of 59 3-digit official and objective occupational codes in managerial and educated classes, their familial genetic risk score (FGRS) for ten major disorders, calculated from 1st through 5th degree relatives. Mean FGRS across disorders were calculated, in 3- and 4-digit occupational groups, and then controlled for those whose disorder onset preceded occupational choice. Using sequential analyses, p values were evaluated using Bonferroni correction.

Results: 3-digit professions considered to reflect creativity (e.g. ‘artists’ and ‘authors’) were among those with statistically significant elevations of FGRS. Among more specific 4-digit codes, visual artists, actors, and authors stood out with elevated genetic risks, highest for major depression (MD), anxiety disorders (AD) and OCD, more modest for bipolar disorders (BD) and schizophrenia and, for authors, for drug and alcohol use disorders. However, equal or greater elevations in FGRS across disorders were seen for religious (e.g. ministers), helping (e.g. psychologists, social workers), and teaching/academic occupations (e.g. professors). The potential pathway from FGRS → Disorder → Occupation accounts for a modest proportion of the signal, largely for MD and AD risk.

Conclusions: While traditional creative occupations were associated with elevated genetic risk for a range of psychiatric disorders, this association was not unique, as similar, or greater elevations were seen for religious, helping and teaching professions and was stronger for internalizing than psychotic disorders.

We found women’s ideas to be more original during ovulation compared to non-fertile phases of the ovulatory cycle

Enhanced Originality of Ideas in Women During Ovulation: A Within-Subject Design Study. Katarzyna Galasinska and Aleksandra Szymkow. Front. Psychol., June 9 2022 | https://doi.org/10.3389/fpsyg.2022.859108

Abstract: The signaling theory suggests that creativity may have evolved as a signal for mates. Indeed, its aesthetic value might not have been necessary for survival, but it could have helped to attract a mate, fostering childbearing. If we consider creativity as such a signal, we should expect it will be enhanced in the context related to sexual selection. This hypothesis was tested mainly for men. However, both men and women display physical and mental traits that can attract a mate. Previous studies showed that women can be more creative during their peak fertility. We advanced these findings in the present study, applying reliable measures of menstrual cycle phases (examining saliva and urine samples) and the highly recommended within-subject design. We also introduced and tested possible mediators of the effect. We found women’s ideas to be more original during ovulation compared to non-fertile phases of the ovulatory cycle. The results are discussed in the context of signaling theory and alternative explanations are considered.

Discussion

The aim of the research was to replicate the study investigating enhanced creative potential of fertile women, with the use of more reliable measures of the phases, and more appropriate within-subject design. We tested women during follicular, ovulation, and luteal phases, hypothesizing to find the effect during ovulation. Our hypotheses were based on the signaling theory (Miller, 2000a), which states that creativity may have evolved as a signal for mates. Although we cannot confirm its role as an indicator of fitness, our study suggests that it may be a mental ornament in women, related to the process of sexual selection (Darwin, 1871). Such an ornament should be manifested in the contexts associated with mating, like, for example, during a fertile phase of the ovulatory cycle.

In our study, originality of ideas was enhanced among fertile women. Originality is called an impression stimulator (Runco, 2007), as it affects attention. This sort of saliency starts at the sensory level (Gaspelin and Luck, 2018). As the most captivating feature of creativity, originality is also found to be the strongest predictor of it (Diedrich et al., 2015). There are also various ways to achieve original ideas. Flexibility of thinking can lead to such ideas through breaking patterns (Runco, 2007). In our study, flexibility was not differentiated in the comparison of three phases. But, it was higher during fertile phase, compared to less fertile phases combined. Different processes may also foster originality, for example persistence (Nijstad et al., 2010). Further studies are needed to test this idea. The fluency dimension was not differentiated either. The probability to generate an original idea increases with the number of ideas. However, the number of ideas is not essential, as a creative person may produce only one idea, but it may be an original one (Acar et al., 2017). Women had a similar quantity, but different quality of ideas. Furthermore, this quantity was quite high in each phase (about 11 ideas on average per phase), so we can assume that participants were generally motivated to produce ideas in the study. We cannot exclude the influence of the pandemic, as partial isolation might have affected participants’ willingness to engage in any kind of activities related to the outside world, creative activities in particular (Karwowski et al., 2021). This generic increased motivation may have also influenced diversity of their thoughts (flexibility), as this dimension was also not differentiated between phases. However, such motivation was not sufficient to produce similarly original ideas in each phase. Thus, it is difficult to interpret differences in originality between phases in the context of isolation, as it was a fixed condition across the phases. Female’s fertility and cycle length are considered to be affected due to illness (Carp-Veliscu et al., 2022) or vaccination (Nguyen et al., 2021). However, the study was conducted in the pre-vaccine (for COVID-19) period. None of the screened participants reported being sick. Morbidity rates during that time were relatively low when we compare them to the following years. However, we cannot exclude asymptomatic cases of COVID-19. We want to emphasize that we did not investigate creativity in participants whose ovulatory cycle was disturbed. The length of all screened cycles was differentiated within a range from 27 to 35 days, so we did not observe notable changes in the cycle length, in the cases when ovulation normally occurred.

Miller (2000a) outlines that creativity, as a subject of selection, concerns a domain associated with aesthetics and fine arts rather than technological innovation. Darwin (1871) pointed to a ‘sense of beauty,’ suggesting a mechanism for mere aesthetics with no direct benefits. Wallace, on the contrary, pointed to the good-gene, utilitarian model, suggesting signals of vigor and vitality behind the signals of beauty, which started a debate on how exactly the mechanisms of sexual and natural selection interact (Prum, 2012; Hoquet and Levandowsky, 2015). Creative ideas are domain-general and defined as novel and useful (Runco, 2007). However, studies indicate that the effect of novelty is larger than usefulness and the latter is not necessarily predictive of creativity (Diedrich et al., 2015). It is also hard to miss the difference between technology and fine arts. The common variance of creativity and intelligence is found to be moderate, and researchers outline the orthogonality of these two constructs (Runco, 2007). Technological creativity would more likely fit the Wallacean utilitarian view of sexual selection processes (Feist, 2001). As divergent and original thinking is assumed to be independent of IQ (Wallach and Kogan, 1965), in our study we have additionally involved a creative convergent thinking test, reflecting the correlation of creativity and intelligence (Lee et al., 2014), and hence more relevant to survival problem solving. Eventually, we found no differences in these abilities between phases. It leads us to an interesting conclusion, corresponding to the problem of utility or/and beauty aspects of sexual selection. Namely, it is possible that convergent creativity could rather be attributed to natural selection processes, while divergent creativity to sexual selection understood after Darwin (1871) as a non-utilitarian, merely aesthetic mechanism of evolution. Thus, our study suggests that two different types of creativity might have evolved, each one focused on solving problems in different domains, namely survival and reproduction. If so, we should expect divergent creativity, but not the convergent one, to be enhanced in the mating context. This is to be verified in future studies.

The significant role of possible mediators would suggest that creativity may be a by-product of another selection. We tested arousal and positive mood, as they can facilitate creativity (Baas et al., 2008). Men could choose women who were more aroused, or more joyful, not directly creative. Creativity, as facilitated by elevated and activating moods, could have developed in parallel. However, although we found these variables increased during the fertile phase (vs infertile phases), we did not detect any mediating effects. Furthermore, both energetic and tense dimensions of mood were the highest during the luteal phase. However, being asked about general arousal, women reported it to be lower comparing to ovulation. We can suppose that during the luteal phase, women experienced mixed emotions. Progesterone may be associated with PMS syndrome (van Wingen et al., 2008), which we did not control unfortunately. But, as estrogen and progesterone act together during the luteal phase, we cannot exclude their interaction in affecting mood in the way we observed. It is important to note, that we awaited the LH peak during ovulation in our study, which usually co-occurs with a pending decrease of estrogen (Reed and Carr, 2018). Direct hormonal measures are needed to explain the mood effects we obtained.

Fertile phase arousal may manifest differently: as a general arousal on the physiological level, but also as mental, sexual, or motoric stimulation, or even as a motivational boost. It is possible, therefore, that the measures we administered might have not been precise enough and they should be more diversified in future studies. We did not control for premenstrual syndrome, which can also be a confounding variable. Finally, we did not control for typing speed (Forthmann et al., 2017), nor the time of day (Breslin, 2019).2

We did not find any differences in cognitive control between the phases; however, this result should be taken with caution. The conditions were not standardized, as the study procedure was conducted via the Internet. Participants’ PC monitors may differ in size and contrast. Additionally, we were not able to check if all participants did the training as we recommended.

To sum up, the present study replicated the effect of enhanced originality of ideas among women during ovulation (Galasinska and Szymkow, 2021). It suggests that originality in divergent creativity is a plausible candidate for mental ornamentation in women. Being boosted during the fertile phase of the cycle, originality presumably increases mate attraction, potentially leading to conception. Nevertheless, it may also promote intrasexual competition to discourage competitors. More contexts should be studied to confirm the hypothesis on the signaling role of creativity. We presented just one of them, showing that with no other incentives, women may manifest some signals of creativity, which may point to its evolutionary legacy.

The belief in free will can be manipulated, showing an increase of deterministic beliefs, but there are no downstream consequences for world views, attitudes or behavior

Manipulating Belief in Free Will and Its Downstream Consequences: A Meta-Analysis. Oliver Genschow et al. Personality and Social Psychology Review, June 8, 2022. https://doi.org/10.1177/10888683221087527

Abstract: Ever since some scientists and popular media put forward the idea that free will is an illusion, the question has risen what would happen if people stopped believing in free will. Psychological research has investigated this question by testing the consequences of experimentally weakening people’s free will beliefs. The results of these investigations have been mixed, with successful experiments and unsuccessful replications. This raises two fundamental questions: Can free will beliefs be manipulated, and do such manipulations have downstream consequences? In a meta-analysis including 145 experiments (95 unpublished), we show that exposing individuals to anti–free will manipulations decreases belief in free will and increases belief in determinism. However, we could not find evidence for downstream consequences. Our findings have important theoretical implications for research on free will beliefs and contribute to the discussion of whether reducing people’s belief in free will has societal consequences.

Keywords: free will, determinism, belief, meta-analysis, morality, cheating, social behavior, punishment

Progressives selected a more unflattering portrait of a typical conservative face than traditional liberals

The Progressive Values Scale: Assessing the Ideological Schism on the Left. Travis Proulx et al. Personality and Social Psychology Bulletin, June 8, 2022. https://doi.org/10.1177/01461672221097529

Abstract: Progressivism has increasingly challenged traditional liberalism as the dominant influence within left-wing ideology. Across four studies, we developed a measure—the Progressive Values Scale (PVS)—that characterizes distinctly progressive values within the left-wing. In Study 1, left-wing participants evaluated divisive issues, with four scale factors emerging. In Study 2, we confirmed this factor structure and included a battery of personality and values measures to explore individual differences among those who maintain a progressive worldview. In Study 3, we achieved final confirmation of the factor structure and validated the ability of the PVS to assess a distinctly progressive perspective, insofar as progressives generated prototypical faces for Liberals and Conservatives that were markedly distinct from those generated by traditional liberals. In Study 4, we distinguished the PVS from measures of left-wing authoritarianism and demonstrated that it is a better predictor of progressive political preferences and social judgments.

Keywords: political psychology, progressivism, liberalism, assessment, values, personality