Study finds testosterone levels influence link between cerebellum density and neuroticism

New research indicates that the amount of gray matter in the cerebellum is linked to neuroticism, and this link is influenced by testosterone levels.

With the help of structural magnetic resonance imaging scans, the study of 149 adolescents and young adults found larger cerebellar gray matter volumes were associated with lower levels of neuroticism. The study also uncovered that in male participants — but not female participants — higher testosterone levels were associated with lower levels of neuroticism and larger cerebellar volumes.

The study was published in the journal Psychoneuroendocrinology. PsyPost interviewed the study’s corresponding author, Dennis J.L.G. Schutter of Radboud University. Read his explanation of the research below.

PsyPost: Why were you interested in this topic?

Schutter: Research has shown that the steroid hormone testosterone has anxiolytic properties and is associated with positive mood states. In spite of findings showing that cerebellar damage can lead to alterations in cognitive functioning as well as mood, the majority of studies focuses on the involvement of the prefrontal cortex. In fact, in a previous study we found an inverse relation between cerebellar gray matter volume and neurotic personality traits which is linked to stress vulnerability and negative mood. Building upon the anatomical fact that the cerebellum has unique direct reciprocal connections to the hypothalamus and that animal studies have demonstrated organizational effects of testosterone on the brain, we were interested in whether the link between cerebellar volumes and neuroticism would be influenced by endogenous levels of testosterone.

What should the average person take away from your study?

The cerebellum is typically seen as a structure associated with motor functions. In the present study further evidence is provided that the cerebellum is linked to non-motor related behaviour. This is the first time study to show that endogenous testosterone levels moderate the relation between cerebellar gray volumes and the tendency to experience stress and negative mood. Our results show that contemporary brain models that emphasize cortico-limbic networks should include the cerebellum, and that testosterone may have neuroprotective properties.

Are there any major caveats? What questions still need to be addressed?

Even though the available literature suggests that testosterone has protective factors both on the neural as well as behavioural level, the correlational nature of our study does not allow to make strong inferences on the direction of the observed relationships. Next to testosterone, the role of the stress hormone cortisol, end-product of the hypothalamic-pituitary-adrenal axis, needs to be addressed. In contrast to testosterone, cortisol has catabolic effects and is positively associated with neuroticism. It is anticipated that the ratio between testosterone and cortisol will have more predictive power in explaining the observed relation between the cerebellum and neuroticism.

Is there anything else you would like to add?

Steroid hormones have significant functional and organizational effects in the brain that contribute to our behavior. It is currently hypothesized that the cerebellum is involved in brain processes related to uncertainty minimization routines. Impairment in these routines compromises psychological resilience and is a risk factor for developing mood disorders.

The study, “Exploring the role of testosterone in the cerebellum link to neuroticism: From adolescence to early adulthood“, was also co-authored by Rosa Meuwese, Marieke G.N. Bos, Eveline A. Crone, and Jiska S. Peper.