Background: Obsessive compulsive disorder (OCD) shares several features with depressive illness (e.g., comorbidity, early escape from dexamethasone suppression, effectiveness of serotonergic pharmacotherapy). It was of interest to establish whether OCD, like major depression, was also associated with immune alterations, notably elevations of circulating natural killer (NK) cells. Method: Circulating lymphocytes were determined from morning blood samples taken from OCD and major depressive patients, as well as from age- and sex-matched controls. Stress perception and coping styles were evaluated in order to assess whether such variables accompanied the NK alterations. Finally, in a subset of patients, symptoms of the illness, stress/coping, and circulating lymphocytes, were also evaluated following 12 weeks of antidepressant medication (serotonergic reuptake inhibitor). Results: The major depressive and OCD patients reported increased perception of day-to-day stresses, coupled with reliance on emotion focused coping styles. Moreover, circulating NK cells were elevated among male OCD and major depressive patients, whereas only a modest increase of NK cells was seen in female major depressives. Twelve weeks of medication alleviated depressive and OCD symptoms, and resulted in normalization of NK cells in the major depressives. However, in OCD patients the reduction of symptoms was not accompanied by significant variations of circulating NK cells. Conclusions: Although major depression and OCD are both accompanied by elevated circulating NK cells, at least in males, normalization of NK cells following treatment was only evident in depression. The persistent elevations of NK cells among male OCD patients may reflect either a trait characteristic of the illness, or symptom reduction and not true remission. Limitations: Although elevations of lymphocyte subsets in major depressive and OCD patients were observed, conclusions concerning immune status in OCD ought to be held in abeyance pending assessment of other indices of immune and cytokine functioning.

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Keywords Depression, Immune, NK cells, Obsessive compulsive disorder, Serotonin reuptake inhibitor
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Journal Journal of Affective Disorders
Ravindran, A.V. (Arun V.), Griffiths, J. (Jenna), Merali, Z. (Zul), & Anisman, H. (1999). Circulating lymphocyte subsets in obsessive compulsive disorder, major depression and normal controls. Journal of Affective Disorders, 52(1-3), 1–10. doi:10.1016/S0165-0327(98)00072-X