In this senes of expenments we explore several behavioral and biological features associated with dysthymic disorder, a subtype of depressive illness characterïzed by chronic, low-grade depression. Although s ymp toms of dy sthymia are less severe, albeit more prolonged, than those associated with major depressive disorder (MDD), dysthymic patients exhibited behavioral dysfunction in many ways sirnilar to that of MDD patients. Specifically, both dysthymic and MDD patients exhibited heightened

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... rception of saessors and diminished positive events relative to controls, while relying on emotionfocused coping strategies at the expense of problem-focused coping. Moreover, iike MDD, dysthymic symptoms were successfully aiIeviated following treatment with a selective serotonin reup take inhibitor (S S RI). While p harmacotherapy assuaged sfressor perception and improved coping strategies, uplift perception was not influenced to the same degree, supporting the notion that despite syrnptom alleviation, residual functional impaimients persisted. In addition to behavioral differences relative to controls, the depres sive patients exhibited elevated circularing lymphocyte su bse ts, particularly n a d killer (NK) ceils. While phamiacotherapy resulted in normalization of C~C U~M~ NK cells in both MDD and dysthymic patients, a more sustained treament interval was required to achieve this effect among the dy sthymic patients. Interestingly, regardless of depressive su btype, significant gender differences were obsented in the levels of circulating NK cells. Although stressor perception was heightened among dysthymic and MDD patients relative to controls, the depressive patients could not be disthguished from controls with respect to their immunological responses to laboratory stressors, such as a cognitive challenges and a clinical interview. However, circulating lymphocytes were exquisitely sensitive to stressors of graded severity. Specifically, arnong nondepressed students exposure to the cognitive challenge and clinical interview resulted in a modest increase of circulating NK cells; however, the more intense stress associated with the anticipation of a ... Ill 1 wouid me to express my sincere gratitude to Dr. Hymie Anisman, for providing guidance, inspiration, and tireless encouragement It has k e n a privilege to work with you.