Stress, Inflammation and Neuroimaging in Major Depressive Disorder as Compared to Premenstrual Dysphoric Disorder

Premenstrual dysphoric disorder (PMDD) is a sex-specific depressive disorder where depressive symptom severity drastically changes in relation to menstrual cycle phase. It is characterized by late luteal phase symptoms of affective lability, irritability, depressed mood, and anxiety. A lot remains unclear and further studies are needed in order to improve the understanding of PMDD and to differentiate it from major depressive disorder (MDD). To date, and in contrast to MDD, the neural correlates of PMDD have been sparsely and poorly investigated. The aim of this study is therefore to investigate the neural correlates of PMDD as compared to MDD and to relate them to stress reactivity. Therefore, three groups of naturally cycling women will be investigated and compared, namely (1) women with MDD, (2) women with PMDD, and (3) healthy control women. Stress and HPA axis activity are assumed to play a crucial role in the development of many mental disorders, including MDD. How stress reactivity and HPA axis activity are connected to PMDD still needs to be investigated. Furthermore, the HPA axis can affect or suppress the activity of the hypothalamic-pituitary-gonadal (HPG) axis, which is involved mainly in the reproductive, but also the immune system, making it an important candidate for the investigation of sex-specific differences in stress reactivity. There are sex-specific differences in stress reactivity, but also in the prevalence of stress-related diseases. Women are twice as likely to suffer from depression than men and the first onset of MDD usually peaks during the reproductive years. As to why these differences exist, a recent theory suggests that ovarian hormone fluctuations function as modulators of women's susceptibility to stress and that altered reactivity to stressors during different cycle phases plays a role in the etiology of depressive disorders. This hypothesis extends the Social Signal Transduction Theory of Depression which first and foremost relates depression to inflammation. They postulate a critical role of cytokines for understanding the pathogenesis of depression. Therefore, ovarian hormone fluctuations, but also inflammation in regard to MDD and PMDD and stress reactivity will be investigated in this study.