Psilocybin microdosing: In a pre-registered, double-blind, placebo-controlled, within-subject crossover design study, they found not affect emotion processing or symptoms of anxiety and depression compared with placebo

Psilocybin microdosing does not affect emotion-related symptoms and processing: A preregistered field and lab-based study. Josephine Marschall et al. Journal of Psychopharmacology, December 17, 2021. https://doi.org/10.1177/02698811211050556

Abstract

Background: Microdoses of psychedelics (i.e. a sub-hallucinogenic dose taken every third day) can reduce symptoms of depression, anxiety and stress according to anecdotal reports and observational studies. Research with medium to high doses of psilocybin points towards potential underlying mechanisms, including the modulation of emotion and interoceptive processing.

Aims: In this preregistered study, we investigated whether psilocybin microdoses alter self-reported interoceptive awareness and whether repeated microdosing over 3 weeks modulates emotion processing and reduces symptoms of anxiety and depression.

Methods: We used a double-blind, placebo-controlled, within-subject crossover design. Participants completed the Multidimensional Assessment of Interoceptive Awareness Questionnaire 1½ h after self-administering their second dose (or placebo), and the emotional go/no-go task and the shortened Depression Anxiety Stress Scale 1½ h after self-administering their seventh dose.

Results: Our confirmatory analyses revealed that psilocybin microdosing did not affect emotion processing or symptoms of anxiety and depression compared with placebo. Our exploratory analyses revealed that psilocybin microdosing did not affect self-reported interoceptive awareness, that symptoms of depression and stress were significantly reduced in the first block compared with baseline, that participants broke blind in the second block and that there was no effect of expectations. Further research in a substance-naïve population with clinical range anxiety and depressive symptoms is needed to substantiate the potential beneficial effects of microdosing.

Keywords: Psilocybin, microdosing, psychedelics, emotion processing, interoceptive awareness, anxiety, depression, symptoms

Discussion

We conducted this study to investigate the effect of repeated psilocybin microdosing on depression and anxiety symptoms, emotion processing and interoceptive awareness. We hypothesized that psilocybin microdosing would reduce symptoms of anxiety and depression, increase the processing time needed to identify negative emotions and increase interoceptive awareness. Our results suggest that the psilocybin microdose did not affect interoceptive awareness, but that there was an effect of the block-order variable. In block 1, the psilocybin-first block-order group had a lower average on two subscales scores of the MAIA compared with the Placebo-first block-order group, but this difference was no longer significant in block 2. We explored the possibility that the psilocybin-first block-order group’s interoceptive awareness increased due to repeated psilocybin microdosing after block 1 and therefore achieved higher scores in block 2 which were more similar to the placebo-first group. However, although there was an increase in average score, this change was not significant. It could well be that the block-order groups already differed in interoceptive awareness at baseline and became more similar in their scores over time regardless of condition assignment – however as we did not assess baseline scores on interoceptive awareness, this possibility cannot be verified.

The effect of repeated microdosing on emotion processing, as measured using an emotion go/no-go task, and symptoms of anxiety, depression and stress also did not differ from placebo. Our finding that psilocybin microdosing does not affect symptoms of anxiety and depression contradicts previous survey studies which reported marked reductions in negative emotionality following the repeated microdosing of psychedelic substances (Anderson et al., 2019; Johnstad, 2018; Polito and Stevenson, 2019). This discrepancy may be due to four key elements in our method, including the mental well-being of our participants at baseline, the use of psilocybin only, the duration of the microdosing period and the inclusion of a placebo condition.

First, our participants were only admitted if our pre-trial screening deemed them as physically and mentally healthy, and their symptoms of anxiety and depression at baseline were within the normal range on average. Johnstad (2018) and Anderson et al. (2019) did not include this criterion within their designs, allowing for participants with clinical range symptoms at baseline. This creates the possibility that their significant reductions in negative emotionality were in part due to higher negative emotionality at baseline, whereas our participants may have experienced a ceiling effect; they were already mentally healthy prior to microdosing and could not show further improvement during the study. However, this argument is countered by Polito and Stevenson (2019) who did explicitly focus on a non-clinical population. They reported low DASS-21 scores at baseline, yet found marked reductions in depression and stress scores. Thus, although the baseline DASS-21 scores of our participants were in the same range as those of Polito and Stevenson (2019), we failed to see additional improvements in our participants’ depression scores after microdosing. However, Polito and Stevenson (2019) did not find a reduction in anxiety scores after microdosing, which does align with our findings. Moreover, post hoc analyses of the DASS-21 subscale scores in comparison with baseline scores did reveal significant reductions in the stress and depression subscales in block 1, but regardless of condition.

Second, previous results demonstrated by Johnstad (2018), Anderson et al. (2019) and Polito and Stevenson (2019) were based on psychedelic microdoses in general, while we chose to focus on specifically psilocybin. It is thus possible that previous results were driven by the effects of psychedelic substances other than psilocybin. However, Bershad and colleagues (2019) investigated the effect of three different microdoses of LSD (6.5, 13 and 25 μg) and also did not find a significant effect of these doses on emotion processing nor on negative emotionality. Relatedly, in our study, we had little control over the specific amount of psilocybin that participants consumed, due to natural variability in different batches of psilocybin-containing truffles. Next to that, it is possible that we also manipulated other active compounds found in the psilocybin-containing truffles and that these influenced our results.

Third, our participants consumed the microdoses for a shorter duration (3 weeks) compared with those in the research by Polito and Stevenson (2019; 6 weeks) and likely in the research by Johnstad (2018) and Anderson et al. (2019), although here the specific duration of microdosing was not reported. While the appropriate time necessary for the benefits of microdosing to take effect is unknown, it is known that serotonergic antidepressants can take up to 2 months before measurable effects arise (Harmer et al., 2009), potentially because their effects are due to certain downstream changes in brain structure and function (Erb et al., 2016; Hanson et al., 2011). The argument that effects of microdoses may also require a longer period of repeated dosing rests on two key findings: that depression and stress-related disorders are associated with neural atrophy in the prefrontal cortex (PFC; Christoffel et al., 2011) and that serotonergic psychedelics can increase structural and functional plasticity in the PFC (Ly et al., 2018; Olson, 2018), thereby potentially counteracting the neurobiological markers of these disorders. It is possible that a period of consistent microdosing which succeeds 3 weeks is required for such changes to develop and we can expect an effect on emotion processing and mood-related symptoms only after these changes have occurred.

Nevertheless, Cameron et al. (2019) administered microdoses of the serotonergic psychedelic DMT to rats every third day for 7 weeks and revealed no markers of increased neural plasticity. In fact, the researchers found a decrease in dendritic spine density in PFC of female rats. Important to note is that the original association between serotonergic psychedelics and neuronal plasticity is based on the effect of a single large serotonergic psychedelic dose. Single large doses of DMT and LSD were found to promote spinogenesis, synaptogenesis and neural plasticity in cortical neuron cultures of rats 24 h after administration (Ly et al., 2018). Taken together, this evidence, although limited in its generalizability to humans, may indicate that regardless of the duration of the dosing period, psilocybin microdoses are simply not potent enough to trigger structural changes in the cortex.

Another factor that could account for the apparent conflict with previous findings is our implementation of a placebo-control group. It is plausible that previous results were driven by participants’ expectations rather than the chemical components of the doses. This would mean that the sole act of taking doses improved participants’ mental health scores, regardless of whether the doses were placebos or psilocybin microdoses. Indeed, Kaertner et al. (2021) found that positive expectancy scores at baseline predicted changes in well-being after 4 weeks of microdosing. In our participants, we observed an overall decrease in the depression and stress scores from baseline to block 1, irrespective of the condition that the participants were assigned to. This effect, termed the ‘placebo effect’, is especially relevant in clinical and pharmacological research and refers to the situation when blinded participants in the placebo condition experience a reduction in symptoms either due to their positive expectations towards the treatment condition or due to previous conditioning of the treatment condition (Meissner et al., 2011). Especially in antidepressant research, placebo doses evoke reductions in symptoms comparable with the antidepressant (Kirsch, 2014). Such potent placebo responses may also be contributing to previous findings regarding the effects of psilocybin microdosing and make it difficult to assess whether psilocybin microdosing is effective beyond expectations and conditioning.

Of relevance, through an exploratory analysis of our participants’ condition guesses, we found that participants broke blind regarding their condition in the second block. This confound had the potential to further contribute to response expectancy effects. However, we found no difference between psilocybin and placebo conditions in our outcome measures in either block, which indicates that explicit expectations likely did not influence our results. Moreover, in contrast to Kaertner et al. (2021), we found no effect of expectation in further post hoc exploratory analyses. We propose two possible reasons for this lack of an effect of psilocybin microdosing on outcome measures: either the placebos and psilocybin microdoses were equally ineffective at influencing a change in response to the scales that we used (potentially the measures were not sensitive enough), or the placebo effect was equally as effective as the microdosing effect but was guided by processes other than explicit expectations, such as previous conditioning (e.g. as demonstrated by Amanzio and Benedetti, 1999). Previous experience with psychedelic substances could evoke a placebo effect based on conditioning. Most participants in this study had taken psychedelics before and may therefore have been subject to such conditioning. Thus, including a placebo condition may have dampened our effect of interest.

Finally, we need to consider the possibility that microdosing does not affect depression and anxiety at all, as our findings consistently indicate. Previously reported beneficial effects may be related to other confounding factors, as mentioned above, and experimental research thus far fails to show these hypothesized effects of microdosing on clinically relevant outcome measures (Bershad et al., 2019; Family et al., 2020).

Limitations

We note five key limitations of our study. First, our sample suffers from selection bias, since participants were self-selected from a microdosing workshop. As a result, most of our participants had tried psychedelics previously, which means that they may have broken blind easier or may have been desensitized to the microdosing effects. Second, the psilocybin doses were made by the participants using dried psilocybin truffles, meaning that we cannot be sure of the exact amounts of psilocybin in the individual doses that the participants consumed. It is possible that the degree of psilocybin content varied across participants and thereby obscured our results. Third, we encountered a large drop-out rate during this project and several participants did not sufficiently comply with the behavioural guidelines to be included in the analyses. This resulted in small sample size relative to existent observational studies and in a further selection bias (i.e. only motivated participants likely stayed in). Moreover, due to such sample size, our study may have been underpowered to detect true effects, particularly the interaction effect hypothesized for the emotional go/no-go task. Our post hoc power analysis suggested that our design, given our observed data, was insufficiently powered to detect this effect. Simulated data in the hypothesized direction, however, yielded sufficient power with a large effect size. Of course, as noted earlier, this analysis based on simulated data remains speculative and we encourage future studies to plan their sample size according to expected RT patterns. Fourth, we measured the effects in our study only after self-administration of a dose, and not between doses or after each block. Thus, our results may be confounded by the acute effect of the psilocybin dose, which may differ from its persistent effect after the acute chemical-induced symptoms have subsided. However, Szigeti et al. (2021) did assess both acute and post-acute effects and found no significant microdose vs placebo differences in psychological outcomes when accounting for participants breaking blind. Last, our study is a combined field and lab-based study, meaning that the results may not be readily generalizable or replicable, for example, in a more clinical setting.

The psychologists with tattoos were viewed as less professional, but the ones with provocative tattoos were seen as more competent in interventions, empathy, ability to practice in a forensic setting, & as more confident, interesting, likable, & less lazy

Zidenberg, A. M., Dutrisac, S., & Olver, M. (2021). “No ragrets”: Public perceptions of tattooed mental health professionals. Professional Psychology: Research and Practice, Dec 2021. https://doi.org/10.1037/pro0000441

Abstract: Clinical psychology students and practitioners are conventionally advised to “cover up” their tattoos, as they may be deemed unprofessional by clients and risk hindering the working alliance. While this may seem reasonable on the surface, the only research available on the topic has focused on psychologists’ self-perceptions and perceptions of tattooed colleagues, which seem to be negative, rather than exploring client perceptions of tattooed clinicians themselves. The present study explored the perceptions of a fictional clinical psychologist profile, including one of three photos (no tattoo, neutral tattoo, or provocative tattoo). Participants were asked to rate the competence of the clinical psychologist, and their feelings toward her. Results indicated that the psychologist with the provocative tattoo was viewed as more competent in the domains of interventions, empathy, ability to practice in a forensic setting, and with adult populations. The psychologist with the provocative tattoo was also rated as more confident, interesting, likable, and less lazy than the psychologist with the neutral tattoo or no tattoo. Although participants rated the two tattooed psychologists as appearing less professional than the psychologist with no tattoo, this did not appear to translate into negative feelings toward the tattooed psychologists or an unwillingness to seek services from them. The results suggest that, contrary to conventional wisdom, psychologists and their trainees may not need to take special precautions to conceal visible tattoos. Tattoos do not seem to impact perceptions of clinician competence among the general public and may even aid the formation of professional bonds with clientele.

Simulation of 100 000 years of evolution in hunter-gatherers: Evolutionary shifts in disgust as polygenic trait occurred (consequence of germ-cell mutations), but cultural transmission between generations operated more quickly & at greater magnitude

The human behavioural immune system is a product of cultural evolution. Edwin S. Dalmaijer, Thomas Armstrong. arXiv Dec 17 2021, https://arxiv.org/abs/2008.13211

Abstract: To avoid disease, humans show far greater contamination sensitivity and avoidance than their closest living relatives. This is driven by an increased propensity to experience disgust. There is broad agreement that uniquely sensitive disgust in humans is an evolutionary adaptation, which was previously thought to be fuelled by both cultural and genetic inheritance. However, current theories have centred biology and sidelined culture, despite surprisingly little empirical evidence to support this claim. Here, we simulated 100 000 years of evolution in human hunter-gatherers to directly compare genetic and cultural inheritance in a variety of scenarios. We modelled disgust avoidance as a trait that governed the extent to which individuals forewent potentially contaminated nutrition to avoid risking gastrointestinal illness. Our results confirmed natural selection for disgust, particularly as the level and cost of contamination in an environment increased. Evolutionary shifts in disgust as polygenic trait occurred as a consequence of germ-cell mutations, but were more prominent in populations with high initial genetic variance. Crucially, cultural transmission between generations operated more quickly and at greater magnitude, even if parental modelling was eliminated. Our computational work supports the hypothesis that cultural evolution outpaced its biological counterpart to select health-improving behaviours that benefited survival. This study serves not only as evidence of cultural evolution shaping the behavioural immune system, but is also an illustration of emerging theories that paint affective and cognitive mechanisms as socially transmitted rather than biologically determined functions.

Meat consumption: Health or environmental information has no main effect on attitude and no effect on intention or behavior

Can information influence meat consumption behaviour? An experimental field study in the university canteen. Nina Weingarten et al. Food Quality and Preference, December 17 2021, 104498. https://doi.org/10.1016/j.foodqual.2021.104498

Highlights

• The study combines an online survey with a field study in a university canteen.

• Aim of the study is to investigate the role of information on meat consumption.

• Health information has no main effect on attitude, intention, or behavior.

• Environmental information has no main effect on attitude, intention, or behavior.

• Subjective knowledge moderates the effect of environmental information on attitude.

Abstract: The present study investigates the effectiveness of health and environmental information provision as an intervention to reduce meat consumption behaviour. In an experimental online survey (n = 194), we tested how information about the negative effects of meat consumption on health or the environment influence attitude and intention to reduce meat consumption. In the following two weeks, we measured participants’ meat consumption behaviour in the university canteen, which we accessed through an individual purchase card. Contrary to our hypotheses, our results show that there is no direct effect of health or environmental information on attitude, intention, or meat consumption behaviour compared to the control group. However, our results indicate that for participants with low subjective knowledge, environmental information is effective in influencing attitude. Neither attitude nor intention mediates the relationship between information and behaviour. Our findings highlight that information provision has limited effectiveness in changing attitude, but does not influence intention or behaviour. We conclude that more research is needed that includes a direct measure of meat consumption behaviour to evaluate the effectiveness of information provision as an intervention.

Keywords: Meat consumptionBehaviourHealth informationEnvironmental informationUniversity canteenSubjective knowledge

Countries that became less wealthy and more morally polarized over time also became less trustful

Stavrova, O., Evans, A. M., & Brandt, M. J. (2021). Ecological dimensions explain the past but do not predict future changes in trust. American Psychologist, 76(6), 983–996. Dec 2021.  https://doi.org/10.1037/amp0000815

Abstract: Concerns about declining trust and rising cynicism are recurrent in academic research and the media. Yet, prior studies focused on explaining, rather than predicting, temporal changes in trust. We tested prediction models of trust change across (up to) 98 countries over six measurement waves (from 1981 to 2014). We tested whether different ecological predictors (e.g., pathogen prevalence, population diversity, inequality) explain the past and predict future trust levels across countries. We used societal growth curve models to disentangle between- from within-country effects and evaluated the accuracy of the models’ out-of-sample predictions using the train-test split method: We used data from 1981–2009 to “train” the models and obtain predictions of trust for the period of 2010–2014. None of our models was more accurate in predicting future trust than a simpler baseline model. Moreover, we did not observe a universal decline in trust. Instead, temporal changes in trust were country-specific, highlighting the locality of cultural change. Most ecological predictors were correlated with between-country differences in trust. Only resource availability and moral opinion polarization were associated with within-country changes in trust: Countries that became less wealthy and more morally polarized over time also became less trustful. These results highlight important differences between explanatory and predictive models and suggest that ecological theories of trust might be of limited use when predicting future cultural shifts.

 

The story of how cognition and fitness relate may not be simple, but simple stories and complex systems rarely go together

Cognition and reproductive success in cowbirds. David J. White, J. Arthur, H. B. Davies & M. F. Guigueno. Learning & Behavior, Dec 16 2021. https://link.springer.com/article/10.3758/s13420-021-00506-0

Abstract: Understanding the relationships between cognitive abilities and fitness is integral to an evolutionary study of brain and behavior. However, these relationships are often difficult to measure and detect. Here we draw upon an opportunistic sample of brown-headed cowbird (Molothrus ater) subjects that had two separate research experiences: First, they engaged in a large series of cognitive tests in David Sherry’s Lab in the Advanced Facility for Avian Research (AFAR) at Western University, then subsequently moved to the Field Avian Research Megalab (FARM) at Wilfrid Laurier University where they lived in large breeding flocks in aviaries with other wild-caught cowbirds. Thus, we had extensive measures of cognitive abilities, breeding behavior, and reproductive success for these birds. We report here, for the fist time, the surprisingly strong connections we found among these different measures. Female cowbirds’ spatial cognitive abilities correlated positively with how intensely they were courted by males, and with their overall egg production. Males’ spatial cognition correlated positively with their ability to engage in singing contests (“countersinging”) with other males. In addition, a separate non-spatial cognitive ability correlated positively with the attractiveness of the songs they sung. In sum, these results suggest the cognitive skills assessed in the lab were strongly connected to breeding behavior and reproductive success. Moreover, since certain cognitive abilities related to different aspects of breeding success, it suggests that cognitive modules may have specialized adaptive value, but also that these specialized skills may interact and influence fitness in surprising ways.

Discussion

Despite the small sample size, the different cognitive scores correlated with several aspects of breeding behavior and reproductive success in both males and females.

Females

Those females who reliably scored highest on spatial tests in the lab received the most courtship song from males. The number of songs sung to females is an important variable associated with pairbond strength and copulation success, and thus is integral to reproduction (White et al., 2010a, b, c). It is unclear what drives this correlation. It is possible that there is something about these females that makes them more attractive to males. Results of past work, however, would suggest that something about the females’ behavior is important in stimulating the males to sing to them more often (Maguire et al., 2013). What females do to get males to sing to them more often is unknown – though one possibility is the use of chatter in response to males’ song (Maguire et al., 2013).

The other variable significantly associated with cognition for females was egg production. Females are often highly variable in egg production between and across groups and past work has been only marginally successful in explaining this variation. Most of those explanations have revolved around the idea that females invest more in egg production in circumstances where they have the most valuable information about the quality of males present (White et al., 2010a, b, c). The cognition score used here is by far the strongest explanatory variable we have ever found for egg production. Perhaps females who have better cognitive abilities can best engage in the behaviors associated with selecting the highest quality, or most compatible mate, building the most successful pairbond, and therefore most likely to invest in egg production. An interesting aspect of this relationship is that laying more eggs leads to a higher spatial memory demand because it requires finding more nests. No matter what mechanism explains this relationship, the connection between spatial cognition and reproductive success suggests that sexual selection can be a driving force on spatial cognition in females.

Males

We had the opportunity to examine how two measures of cognitive performance related to males’ fitness. First, we found that song attractiveness, as measured in playback tests related to the males’ performance on cognitive tasks that used color stimuli in delayed match-to-sample tests. That song attractiveness related to cognitive performance supports the theory that those males best able to learn are the ones who can produce the most attractive signal – a theory of the functional value of song that has been posited for songbirds in general (Nowicki et al., 1998, 2002) and cowbirds specifically (West & King, 1988). These results connecting cognitive performance and song differ from work in song sparrows (Soha et al., 2019), where no connections between cognition and song could be detected (see also Templeton et al., 2014). Why song attractiveness should relate to cognition for color per se, is unclear. Perhaps song attractiveness and performance on the color tasks are linked by another unmeasured variable relating to male quality (health, “good genes”, or stress responsiveness). This would appear unlikely since past work has shown that song attractiveness is highly dependent on developmental (West & King, 1988) and immediate (Gersick & White, 2018) social experiences. Thus, the most likely route leading to variation in song attractiveness involves interacting and learning from the visual responses of females and other males to singing overtures. The color tasks were designed as a control for spatial memory performance and not designed specifically to examine an aspect of cognition hypothesized to be important to male breeding behavior. Thus, the color tasks may be measuring some more general aspect of visual acuity, attention, or learning. More work is needed to determine exactly what cognitive mechanism is driving color discrimination and song development. It is clear, however, that the cognitive ability measured using the color task was distinct from spatial memory skill because performance on spatial tasks did not relate to song attractiveness.

Spatial task performance did, however, relate to one important aspect of singing in males: countersinging. Countersinging is a skill that males must learn in order to attain and maintain dominance among males and to stimulate the reproductive output of females (White et al., 2010a, b, c). Past work has shown that countersinging is learned by juveniles over their first year of life as they approach and sing with adult males (White, King, & West, 2002a). This ability to get close to other males, sing with them in duetting bouts, and temper aggression leads to a cascade of learning other breeding skills and is highly variable among males (White et al., 2007a, b; White, King, & West, 2002a).

No other variables for males or females reached the large effect size necessary for statistical significance (other than chatter patterns in females). There is, however, a distinction that should be made between the correlation strength needed for statistical confidence and for biological relevance. Evolution can act on very small effects. Tables 1 and 2 show some of the effects that did not reach significance but will be the subject of future work, as many of them may inform us of the potential directions of effect occurring with other variables. For example, female chatter is highly stimulating and motivating to males (Burnell & Rothstein, 1994; Freed-Brown & White, 2009; Hauber et al., 2001; Lynch et al., 2017; Snyder-Mackler & White, 2011). Perhaps the production and use of chatter is a behavioral mechanism that females use to regulate males’ behavior, stimulate courtship effort, and strengthen the pairbond (Maguire et al., 2013), leading eventually to more egg output. Other interesting positive relationships with females’ spatial cognition include the song attractiveness of their pairmate, and the amount of courtship song they receive only from their pairmate (a measure of pairbond strength we have found in the past to be important for breeding success; Maguire et al., 2013).

The disclaimers here are most likely obvious: the frustratingly low sample size highlights the challenges for neuroecology and studies of animal cognition in general where the depth of understanding of individuals’ cognitive abilities trades off against testing large numbers of subjects and therefore against generalizability and statistical power. The low number of subjects precluded more detailed statistical analyses, and we could only rely on a small number of a priori comparisons requiring very strong relationships to reject a null hypothesis. Also, the birds in this study, while wild caught, experienced years of life in abnormal contexts, raising questions about generalizability to the wild (although in the aviaries they bred in patterns very similar to the resident birds). Finally, it was not the primary goal of the cognitive experiments to subsequently study fitness. Had it been, we would have ensured that we collected measures that were more directly comparable across subjects. As is, it is not clear what cognitive modules we are examining here. The color-discrimination tasks might be measuring visual acuity, attention, learning speed, etc. Spatial cognition here also includes tasks that were focused on numerical discrimination. Thus, this work should be considered an exploratory first step that, even with the limitation inherent in these data, was surprisingly successful in demonstrating relationships between different aspects of cognition and reproductive success. This discovery will drive experiments both in the lab and in aviaries for years to come.

What do these findings mean for the adaptive specialization hypothesis about cowbird spatial memory? We still have not been able to test directly whether spatial cognition abilities allow females to successfully find and select viable nests in the wild – the critical relationship posited by the adaptive specialization hypothesis that started the work with cowbirds. With modern advances in automated tracking technology and advances in neural manipulations, this relationship may be testable in the near future. The findings reported here – that different measures of cognition related to different aspects of effective breeding – support the idea that there are functionally distinct cognitive systems as proposed by Sherry and Schacter (1987). There do seem to be different cognitive domains at work here, similar to food-caching species that show different patterns of performance depending on whether a task is spatially based or color based (Olson et al., 1995). Females’ superiority in behavioral tasks and the hippocampal size evidence suggest that the potential exists for selection to act on spatial cognition through nest-finding abilities. The interconnections between these cognitive systems and diverse aspects of breeding revealed here, however, suggests some cooption, or exaptation of the cognitive system, which significantly complicates determining how selection has acted and may act (Gould & Vrba, 1982; Sherry & Schacter, 1987). Selection may be operating on spatial memory skills for both a specialized demand on the species (finding nests), and also a non-specialized demand (selecting a mate and reproducing). This suggests there are non-additive interactions among cognitive modules and fitness.

The story of how cognition and fitness relate may not be simple, but simple stories and complex systems rarely go together. The complexity of living systems presents many different routes and strategies leading to reproductive success and thus identifying how distinct memory systems relate to fitness can be challenging. Studying the wealth of links between memory systems, however – how they can work independently and together, how they react to different environments, to past experiences and to conspecifics – and ultimately lead to organizing adaptive behavior holds the promise to fully understand the evolution of the brain and intelligence.

Several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions; low birth weight, smallness relative to gestational age and preterm birth with non-violent convictions were higher for men

Adverse perinatal events and offspring criminal convictions in men and women: A population-based study. Sofi Oskarsson et al. Journal of Criminal Justice, Volume 78, January–February 2022, 101879. https://doi.org/10.1016/j.jcrimjus.2021.101879

Highlights

• Adverse perinatal events were associated with an increased risk of violent and non-violent criminal offending

• Associations between some adverse perinatal events with criminal convictions were significantly higher for men than for women

•There was a dose-dependent association between adverse perinatal events with criminal convictions for both men and women

Abstract

Background: We examined associations of adverse perinatal events with offspring violent and non-violent criminal convictions in men and women.

Methods: All singleton births between 1973 and 1995 (n = 1,146,570 men, n = 1,085,217 women) were identified through Swedish population-based registers. Information about adverse perinatal events was retrieved from the Medical Birth Register. Outcomes were criminal convictions collected from the National Crime Register. We estimated absolute and relative risks of being convicted of criminal convictions using the Kaplan-Meier method and survival analyses for men and women separately. We also tested for differences in magnitudes of associations for men versus women.

Results: Several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions in both men and women. Associations between low birth weight, smallness relative to gestational age and preterm birth with non-violent criminal convictions were statistically significantly higher for men than for women. There was a dose-dependent association between adverse perinatal events with violent and non-violent criminal convictions for both men and women, indicated by the strengthened magnitude of HR estimates with exposure to an increasing number of adverse perinatal events.

Conclusions: Adverse perinatal events are associated with violent and non-violent criminal convictions in men and women, with some differences in risk estimates between sexes. Findings are compatible with theoretical accounts implicating disruption of the neurodevelopment during the perinatal period.

4. Discussion

In this large-scale population-based study, we found that several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions. These results are not only in line with findings from previous research (Liu et al., 2009), but also extend these. Specifically, we add to the existing literature by showing that the exposure to adverse perinatal events increases the risk of violent and non-violent criminal convictions, in both men and women. Further, we found evidence for a dose-dependent relationship between adverse perinatal events and criminal behavior, whereby the exposure to an increasing number of adverse perinatal events elevated the risk for violent and non-violent convictions in both men and women. Additionally, our findings suggest that there may be different adverse perinatal events that heightened the risk of violent and non-violent criminal convictions for men compared to women, even though they are few. For example, observed associations for low birth weight and preterm birth with non-violent criminal convictions were significantly higher for men than for women. These findings build on the existing knowledge regarding the potential importance of early risk factors for criminal offending and point to a dose-dependent relationship.

We also found that small head circumference at birth was associated not only with violent criminal convictions as reported in earlier studies (Ikäheimo et al., 2007) but also with non-violent criminal convictions. These findings were evident for both men and women. Small head circumference has in the previous literature been referred to as a minor physical anomaly (Denno, 1990). From a biopsychosocial criminological perspective, minor physical anomalies have been viewed as reflecting physical and neural maldevelopment of the fetus during pregnancy, potentially due to both genetic and environmental influences (Raine, 2002b; Raine, 2019). Minor physical anomalies have long been a known correlate of male aggression (Waldrop et al., 1978) and criminality (Raine, 2013), but the current results indicate that this association extends to criminal offending among women.

One previous study using a sample that overlapped partly with the present study's, reported a reduced risk of any criminal conviction among offspring who were born preterm (D'Onofrio et al., 2013). This association remained even among discordant siblings, pointing to an independent association between being born preterm and later criminal offending. Being born preterm would thus serve as a protective factor for later criminality. We found that in models adjusted for birth year, preterm birth increased the risk for violent and non-violent criminal convictions among men, but not women. However, in mutually adjusted models, preterm birth was associated with violent criminal convictions but not non-violent convictions, among men, but not women. The discrepancy in findings may be due to the fact that the present study examined men and women separately, whereas the previous study (D'Onofrio et al., 2013) used a total population sample with an adjustment for offspring sex. Another explanation may relate to the different outcomes studied: whereas the present study utilized violent and non-violent criminal convictions as separate outcomes and D'Onofrio et al. (2013) employed any criminal conviction as the outcome.

Taken together, these findings highlight the importance of examining men and women separately when studying associations between adverse perinatal events and criminal convictions, as well as studying violent and non-violent criminal convictions as separate outcomes. The male brain has been suggested to be more susceptible to influences early in life that can disrupt normative neurological development (Golding & Fitzgerald, 2019), and it is well-known that preterm birth is associated with behavioral and psychological problems in later life (Bhutta et al., 2002). Our findings suggest that the association between preterm birth and criminal offending should be further investigated to better understand whether this is a factor contributing to the higher overall rate of criminal convictions for men as compared to women.

One previous study has demonstrated associations between adverse perinatal events and later self-reported violent behavior in a dose-dependent manner, among both men and women (Murray et al., 2015). Our results are in line with these findings and suggest that when adverse perinatal events accumulate in the same individual (up to four for men and up to three for women in the present study), the risk for criminal convictions in the offspring increases for both men and women. The dose-dependent association between adverse perinatal events and offspring criminality is in line with biopsychosocial criminological theory, which suggest that adverse perinatal events contribute to a disruption of neuropsychological development, which in turn can heighten the risk for criminal behavior (Raine, 2002c). It is possible that the accumulation of adverse perinatal events in the same individual index disruption of fetal development during pregnancy more effectively than exposure to a single event. This may further be why we see relatively weak associations between individual adverse perinatal events with offspring criminal convictions, as well as low cumulative incidences, even though there are some indications that certain adverse perinatal events are more important than others (e.g., smallness for gestational age). Further research is needed to clarify the nature and etiological basis of the dose-dependent association between perinatal events and later criminal behavior in offspring, which in turn can inform clinical practice and possibly prevention efforts.

Interestingly, the adverse perinatal events that evidenced an association with criminal offending in the mutually adjusted models differed for men and women. For men, the summative index encompassed extremely low and low birthweight, small for gestational age, small head circumference, and post-term birth for non-violent criminal convictions, with the addition of preterm birth for violent criminal convictions. For women, the summative index encompassed of low birth weight, small head circumference, and post-term birth. The implication is that certain adverse perinatal events, when accounting for all others, are more important for men than for women and vice versa. We opted for an empirically driven approach that allowed for different adverse perinatal events to be included in the summative indices for men and women respectively. Our results highlight the need to differentiate between men and women in the study of adverse perinatal events in relation to criminal convictions, since men and women likely are at different risk of experiencing adverse perinatal events (Zeitlin et al., 2002), as well as engage in criminality. This approach was further supported by the HR estimates for the summative index in the total population (Table S3 in Supporting Information), which in general were not significant or in most cases exhibited overlapping CIs. The dose-dependent relationship between adverse perinatal events and offspring criminal behavior should be explored more extensively in future research to better understand the differences between men and women.

Some unexpected findings in our study should also be noted. Certain adverse perinatal events were associated with a decreased risk of violent and non-violent criminal convictions (e.g., breech presentation, assisted vaginal delivery). Breech presentation, as well as other adverse perinatal events, have previously been related to a lack of oxygen to the fetus (i.e., anoxia), which in turn has been described as a risk factor for criminal offending (Tibbetts, 2011). No study thus far has specifically examined breech presentation in relation to criminal offending, let alone different types of breech positions (e.g., frank breech, complete breech). Further research using other samples is needed to explicate the role of different breech presentations and other aspects of delivery on risk for later criminality.

In our sensitivity analyses, we stratified the full sample including men and women based on levels of SES. Previous work has reported associations between exposure to adverse perinatal events in combination with psychosocial adversities, such as maternal rejection (Raine et al., 1994; Raine et al., 1997) and a disadvantaged family environment (Piquero & Tibbetts, 1999) and later criminal behavior in the offspring. However, a few exceptions should be noted though (Murray et al., 2010; Murray et al., 2015). In the current study, HR estimates were largely unaffected by stratifying the sample into levels of SES, if anything they were somewhat attenuated for all groups.

Findings from the present study should be considered in the light of certain limitations. Some of our reported associations, particularly those for the female portion of the sample, need to be interpreted with caution because of the small number of individuals being exposed to particular adverse perinatal events, as well as the small portion of criminal offenders among females. Owing to these factors, HR estimates for females were less precise than those for males, with wider confidence intervals.

Another limitation is that, although the great majority of births in Sweden are recorded in the MBR, there are still 1–3% of all births during each of the past 20 years that are missing from the register (the National Board of Health and Welfare, 2021). While the MBR contains information of varying quality, the adverse perinatal events included in the present study have previously shown high validity (Källén & Källén, 2003). It is also important to acknowledge that our criminal convictions data relied on official records, which may not be representative of all men and women who have engaged in criminal activity. While registry data reduces the risk of misclassification in one way by limiting recall bias that is often associated with interview data, the results in the present study assume the same level of misclassification of criminal convictions for men and women. While more research is needed on this specific topic, especially in relation to registry data, there is some evidence for a more lenient treatment of female offenders as compared to male offenders (Doerner & Demuth, 2014). Lastly, we performed sensitivity analyses in the total sample of men and women, stratified on levels of SES. Ideally, this would have been done in men and women separately but was not possible due to statistical power restrictions.