Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Neuroscience

Supervisor

Hampson, Elizabeth

Abstract

Recent findings suggest that insufficient testosterone levels may be associated with depressive affect in men. Genetic variability in the androgen receptor (polyglutamine [CAG] repeat length) may be important for this relationship. However, the relationship between testosterone, androgen receptor CAG repeat length, and depressive affect remains inconclusive. The current thesis examined the association between testosterone concentration, androgen receptor CAG repeat length, and depressive affect in 218 young men with diverse mood patterns. Saliva samples were collected to quantify bioavailable testosterone, cortisol, and CAG repeat length. Participants completed the Profile of Mood States scale. In men with low testosterone concentrations, lower testosterone and longer androgen receptor CAG lengths predicted greater negative affect. Testosterone, CAG length, and negative affect were unrelated in men with average or higher testosterone concentrations. Cortisol concentrations were not related to negative affect. These findings suggest a complex relationship between testosterone and depressive affect in young men.

Summary for Lay Audience

The regulation of mood is a complex process, and no single model can explain all aspects of mood, or the emergence of pathological mood states like depression. For example, biological, psychological, and environmental mechanisms can all contribute to different mood states in different individuals, as well as the development of mood disorders. Of the biological mechanisms, little is known with respect to the role of the sex hormone testosterone (T) in mood regulation in men. Recent research suggests that insufficient T activity may increase the risk of depressive affect in men. T achieves its effects in the human body primarily by binding to the androgen receptor (AR). Consequently, genetic variability in the AR which produces differences in AR function may be important for understanding the relationship between T and mood regulation. Specifically, a variable polyglutamine (CAG) repeat length within the AR gene produces differences in AR activity and may contribute to mood states, as well as an increased risk of depression. However, the relationship between T levels, AR CAG repeat length, and depressive affect in men remains inconclusive. Consequently, the current thesis sought to investigate the statistical relationship between T activity and depressive affect in 218 physically healthy young men. Participants attended a single test session in our laboratory. Saliva samples were collected to quantify bioavailable T and cortisol levels, as well as to measure AR CAG repeat length. Participants completed the Profile of Mood States (POMS), a standardized mood scale, to measure recent mood, including depressive affect. Principal components analysis of the POMS identified 7 mood components, including a Negative Affect (NA) component. For men with low circulating T concentrations, lower bioavailable T and longer AR CAG repeat lengths were predictive of greater NA. A relationship between T activity and NA was not found in individuals with average or higher T concentrations. Circulating cortisol concentrations were unrelated to NA. The findings of the current thesis suggest a complex relationship exists between circulating T and negative mood in young men, and that levels of bioavailable T may influence the intensity of depressive affect experienced.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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