Schizophrenia: The new etiological synthesis

Schizophrenia has been an evolutionary paradox: it has high heritability, but it is associated with decreased reproductive success. The causal genetic variants underlying schizophrenia are thought to be under weak negative selection. To unravel this paradox, many evolutionary explanations have been suggested for schizophrenia. We critically discuss the constellation of evolutionary hypotheses for schizophrenia, highlighting the lack of empirical support for most existing evolutionary hypotheses—with the exception of the relatively well supported evolutionary mismatch hypothesis. It posits that evolutionarily novel features of contemporary environments, such as chronic stress, low-grade systemic inflammation, and gut dysbiosis, increase susceptibility to schizophrenia. Environmental factors such as microbial infections (e.g., Toxoplasma gondii) can better predict the onset of schizophrenia than polygenic risk scores. However, researchers have not been able to explain why only a small minority of infected people develop schizophrenia. The new etiological synthesis of schizophrenia indicates that an interaction between host genotype, microbe infection, and chronic stress causes schizophrenia, with neuroinflammation and gut dysbiosis mediating this etiological pathway. Instead of just alleviating symptoms with drugs, the parasite x genotype x stress model emphasizes that schizophrenia treatment should focus on detecting and treating possible underlying microbial infection(s), neuroinflammation, gut dysbiosis, and chronic stress.</p

Toxoplasma gondii and Psychopathology: Latent Infection Is Associated with Interpersonal Sensitivity, Psychoticism, and Higher Testosterone Levels in Men, but Not in Women

Objective The ability of parasites to hijack the nervous system, manipulating the host's physiology and behavior in ways that enhance the parasite's fitness while damaging host fitness, is a topic of ongoing research interest in evolutionary biology, but is largely overlooked in mental health research. Nevertheless, recent evidence has shown that Toxoplasma gondii infection can change host testosterone levels and influence the development of some psychiatric disorders. Here, we tested this hypothesis in a mixed sample of 213 non-clinical subjects.Methods Participants (n(males) = 108, n(females) = 105) provided 5 ml of blood to quantify testosterone levels and Toxoplasma gondii antibodies. The Symptom Checklist-90-Revised was used to assess psychopathological symptoms.Results The results showed that Toxoplasma-infected men had higher testosterone levels and scored higher in Interpersonal Sensitivity and Psychoticism symptoms than non-infected men. Toxoplasma-infected women did not differ from control women.Conclusions Framed in an evolutionary framework, the findings suggest that the elevated testosterone levels and the expression of psychopathological symptoms can be seen as the result of the manipulation exerted by Toxoplasma gondii either to reach its definitive host or to increase its spread. Future research can benefit from integrating insights from evolutionary biology and parasite-host interactions with physiology, immunology, and mental health to develop a better understanding of mental health etiology.</div

Self-Perceived Facial Attractiveness, Fluctuating Asymmetry, and Minor Ailments Predict Mental Health Outcomes

Objective Phenotypic markers associated with developmental stability such as fluctuating asymmetry, facial attractiveness, and reports of minor ailments can also act as indicators of overall physical health. However, few studies have assessed whether these markers might also be cues of mental health. We tested whether self- and other-perceived facial attractiveness, fluctuating asymmetry, and minor ailments are associated with psychopathological symptoms in a mixed sample of 358 college students, controlling for the effects of body mass index, age, and sex.Methods We applied the Symptom Checklist-90-Revised (SCL-90-R) questionnaire to assess psychopathological symptoms, a battery of questionnaires about self-perceptions of facial attractiveness, and gathered information about the number of previous minor ailments as well as demographic data. Other-perceived attractiveness was assessed by an independent mixed sample of 109 subjects. Subjects' facial fluctuating asymmetry was determined by geometric morphometrics.Results The results revealed that in both men and women, higher self-perceived attractiveness and fewer minor ailments predicted lower scores of Somatization, Obsessive-Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Phobic Anxiety, Paranoid Ideation, Psychoticism, and a General Psychopathology Index. Higher facial fluctuating asymmetry was associated with higher Interpersonal Sensitivity, but did not contribute to its prediction when controlling for the other studied variables.Conclusions The observed strong associations between self-perceived attractiveness, minor ailments, and psychopathology indicate common developmental pathways between physiological and psychological symptomatology which may reflect broader life history (co)variation between genetics, developmental environment, and psychophysiological functioning.</p

Socioeconomic position, immune function, and its physiological markers

The development of costly traits such as immune function and secondary sexual traits is constrained by resource availability. The quality of developmental conditions and the availability of resources in ontogeny may therefore influence immune system functions and other biological traits. We analyzed causal pathways between family socioeconomic position, strength of immune response, and five physiological biomarkers in young Latvian men (n = 93) using structural equation modeling. Men from wealthier families had higher testosterone levels (rs = 0.280), stronger immune response (rs = 0.551), and higher facial attractiveness (rs = 0.300). There were weak, non-significant correlations between family income, body fat percentage (rs = −0.147), and fluctuating asymmetry (rs = −0.159). Testosterone partially (33.8%) mediated the effect of family income on facial masculinity. Testosterone (positively) and adiposity (negatively) partially (4%) mediated the relationship between family income and immune function. Higher facial masculinity, higher facial symmetry, and lower adiposity were reliable and independent cues of better immune function (R2 = 0.238) in a larger sample of young Latvian men (N = 146). Resource availability in ontogeny has an important role for the development of immune function and physical appearance, and it is a key parameter to be included in human eco-immunological research

Javier I. Borráz-León's Quick Files

The Quick Files feature was discontinued and it’s files were migrated into this Project on March 11, 2022. The file URL’s will still resolve properly, and the Quick Files logs are available in the Project’s Recent Activity

Choosing Fighting Competitors Among Men: Testosterone, Personality, and Motivations

Higher testosterone levels have been positively related to a variety of social behaviors and personality traits associated with intrasexual competition. The aim of this study was to evaluate the role of testosterone levels and personality traits such as aggressiveness, competitiveness, and self-esteem on the task of choosing a fighting competitor (a rival) with or without a motivation to fight. In Study 1, a group of 119 men participated in a task for choosing a rival through pictures of men with high-dominant masculinity versus low-dominant masculinity. Participants completed three personality questionnaires and donated two saliva samples (pre-test and post-test sample) to quantify their testosterone levels. We found that the probability of choosing high-dominant masculine men as rivals increased with higher aggressiveness scores. In Study 2, the task of choosing rivals was accompanied by motivations to fight (pictures of women with high or low waist-to-hip ratio [WHR]). In this context, we observed that the probability of choosing dominant masculine men as rivals depended on the WHR of the women. Overall, average levels of post-test testosterone, aggressiveness, and high self-esteem increased the probability to fight for women with low WHR independently of the dominance masculinity of the rivals. Our results indicate that human decisions, in the context of intrasexual competition and mate choice, are regulated by physiological and psychological mechanisms allowing men to increase their biological fitness. We discuss our results in the light of the plasticity of human behavior according to biological and environmental forces

Cortisol reactivity to psychosocial stress in vulnerable and grandiose narcissists: An exploratory study

Introduction: Narcissistic personality manifests itself in at least two different forms: grandiose and vulnerable. In the present study, we compared cortisol and emotional responses to psychosocial stress between subjects high in vulnerable and grandiose narcissism scores, and examined possible associations between narcissism, other personality traits, and stress responses. We hypothesized that subjects with higher scores of vulnerable narcissism would show stronger emotional and physiological reactivity than those with high scores of grandiose narcissism. Methods: A final sample of forty-seven participants underwent a Trier Social Stress Test (TSST), provided saliva samples to assess cortisol levels, and completed several personality questionnaires. Results: Consistent with our hypothesis, subjects with higher scores of vulnerable narcissism had a stronger cortisol and emotional response than those with high scores of grandiose narcissism. Vulnerable narcissism was positively correlated with schizotypal traits, while grandiose narcissism was positively correlated with psychopathic traits. Participants with a mixed-type of narcissism were also discussed. Discussion: This study provides the first evidence of differential physiological and emotional reactivity to social evaluation threat according to scores of vulnerable and grandiose narcissism. Since this is an exploratory study, the results must be interpreted with caution. However, the results will be informative for future confirmatory research with larger and more heterogeneous samples.</p