Date of Award

Spring 5-2016

Author's School

Graduate School of Arts and Sciences

Author's Department

Psychology

Degree Name

Master of Arts (AM/MA)

Degree Type

Thesis

Abstract

Elevated stress perception and depression commonly co-occur and have shared genetic and environmental influences, suggesting they may rest upon a common underlying neurobiology. The rostral middle frontal gyrus (RMFG), part of the dorsolateral prefrontal cortex, is critical for executive function, including emotion regulation and working memory. Variability in RMFG cortical thickness has been associated with both depression and stress-related phenotypes, although the directionality of these associations has been inconsistent thus far. The current study examined healthy participants (n=879) who completed the ongoing family-based Human Connectome Project were included in analyses. RMFG cortical thickness was computed from structural magnetic resonance imaging (MRI) scans using FreeSurfer. Depression symptoms, positive affect, personality traits, and perceived stress were assessed using self-report questionnaires: the PROMIS depression scale, the PANAS-X, and the PSS, respectively. After accounting for effects of sex, age, ethnicity, average whole-brain cortical thickness, twin status, and familial structure, as well as correcting for multiple tests, bilateral RMFG thickness was associated with increased perceived stress (left RMFG: p=.0017; right RMFG: p=.0013). Moreover, left RMFG cortical thickness was significantly positively associated with depressive symptoms (p=.0053) and negatively associated with positive affect at levels approaching significance after correcting for multiple testing (p=.0196). Follow-up simultaneous linear models revealed unique associations between bilateral RMFG cortical thickness and perceived stress when accounting for associations with positive affect and depressive symptoms. Heritability analyses showed that bilateral RMFG thickness, depressive symptoms, and perceived stress were all significantly heritable. After decomposing variability between the constructs, shared genetic and environmental contributions to variability were observed among self-reported sadness, positive affect, and perceived stress, as well as between right and left RMFG cortical thickness. Collectively, these findings suggest that increased RMFG cortical thickness is associated with depressive symptoms and linked to the subjective perception of stress. More broadly, these results suggest that stress perception and depressive symptoms share a common underlying biology. What remains unclear from this cross-sectional study is the origin of individual differences in RMFG cortical thickness: it is possible that stress exposure and/or the presence of depressive symptoms may give rise to differences in brain structure, or it may be the case that increased RMFG thickness contributes to stress-related cognitive biases that promote vulnerability to depression.

Language

English (en)

Chair and Committee

Deanna Barch

Committee Members

Ryan Bogdan, Thomas Rodebaugh

Comments

Permanent URL: https://doi.org/10.7936/K7BR8QGX

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