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What are the implications of individual differences and sex differences in the oxytocin and vasopressin systems for human mental health?
Tanya Procyshyn1, Bernard Crespi1
1Department of Biological Sciences, Simon Fraser University
On-going Research Objectives
Develop and test models of interactions between hormones, hormone receptor genes, and social behaviour and cognition
Improve understanding of sex differences in the effects of oxytocin and vasopressin on human social behaviour and cognition
Improve understanding of how individual differences and sex differences in hormone systems relate to risk of mental health disorders, particularly autism and schizophrenia
Current Research
To further develop and test our proposed models, we are collecting data that allow us to examine multiple hormones and multiple dimensions of hormone systems simultaneously. The protocol is as follows:
Problem Statement
Mental health disorders remain an important issue in Canada. One approach to better understanding mental health disorders is to analyze what adaptive systems are dysregulated in mental health disorders and how they are dysregulated. Such information may be useful for developing new treatments and therapies.
Hormones & Mental Health Disorders
Growing evidence suggests that hormone systems, which motivate and modulate many aspects of cognition and social behaviour, are dysregulated in common mental health disorders. Dysregulation may relate to the hormone itself (level of hormone present deviates from optimum) or to the receptors that hormones bind to in the brain (number of receptors or sensitivity deviates from optimum).
Oxytocin & Vasopressin
Closely-related hormones with distinct functions in brain & body
Evolutionarily ancient mediators of sociality that influence social behaviour in diverse taxa from fish to humans
May have “pro-social” effects: associated with social bonding, cooperation, communication, trust, and empathy 1
Interact with sex hormone systems to have different - sometimes opposite - effects on social behaviour in males and females 2
Implicated in many mental health disorders, including disorders with sex differences in prevalence rates 3
Hypothesized multi-hormone model of sex differences in risk of mental health disorders. Adapted from (3).
Vasopressin 1A Receptor & Autistic-Like Traits
Multiple studies have linked variation in the vasopressin 1a receptor (AVPR1a) gene with autism risk in clinical populations, as well as with reduced social behaviour in general populations5. We tested if AVPR1a variation was associated with autistic-like traits in a population of university students. .
Method
DNA was obtained from 873 research participants. Two AVPR1a microsatellites associated with autism risk, RS1 and RS3, were analyzed by length. Participants also completed the Autism Quotient questionnaire, which quantifies five domains altered in autism spectrum disorders: social skill, communication, attention switching, imagination, and attention to detail. Statistical tests were performed to assess differences in average Autism Quotient scores between AVPR1a genotype groups (short/short, short/long, long/long).
Results
The AVPR1a RS3 long/long genotype group and carriers of a specific RS3 variant (the 327bp “target allele” associated with autism risk and reduced altruism and pair-bonding) had significantly higher Autism Quotient scores (p = , males and females). This difference was due mainly to the attention switching measure. When the data were analyzed for sex differences, the relationships were significant only for females.
Conclusions
These results support that individual differences in the vasopressin system relate to autistic-like traits in healthy individuals, establishing continuity with previous studies. The results also highlight the need to test for sex differences when studying the effects of hormones on social behaviour or cognition.
Saliva sample collection to measure baseline hormone levels (oxytocin, vasopressin, testosterone) via ELISA.
Viewing of an empathy-inducing video known to increase oxytocin levels.6
Sites of variation in the human vasopressin receptor 1a gene.5
Saliva sample collection to assess post-video changes in hormone levels.
Questionnaires assessing autistic-like traits, schizophrenia-like traits, empathy, etc.
DNA collection to analyze genes relating to hormone systems. (oxytocin receptor, vasopressin 1a receptor, androgen receptor)
Data analysis to examine relationships between baseline hormone levels, hormone reactivity, hormone receptor genes, and questionnaire scores in males and females.
Works Cited
1 Donaldson, Z. R., & Young, L. J. (2008). Oxytocin, vasopressin, and the neurogenetics of sociality. Science.
2 Dumais, K. M., & Veenema, A. H. (2015). Vasopressin and oxytocin receptor systems in the brain: Sex differences and sex-specific regulation of social behavior. Frontiers in Neuroendocrinology.
3 Crespi, B. (2015). Oxytocin, testosterone, and human social cognition. Biol. Rev.
4 Cochran, D., Fallon, D., Hill, M., and Frazier, J. (2013). The role of oxytocin in psychiatric disorders: A review of biological and therapeutic research findings. Harv Rev Psychiatry.
5 Meyer-Lindenberg, A., Domes, G., Kirsch, P., & Heinrichs, M. (2012). Oxytocin and vasopressin in the human brain: social neuropeptides for translational medicine. Nature Reviews Neuroscience.
6 Barraza, J. A., & Zak, P. J. (2009). Empathy toward strangers triggers oxytocin release and subsequent generosity. In Annals of the New York Academy of Sciences.
Known associations between hormone systems and common mental health disorders. 2, 3, 4
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