Researchers investigated immune function and health outcomes in women with depression, as compared with a non-depressed control group. Depression is a biological, psychological, and social illness that affects roughly 15 million American adults in any given year. Depression costs billions of dollars in lost time, productivity, personnel replacement, medical care and, tragically, loss of life. The cost to women is disproportionally higher, with women representing about two-thirds of those affected .
According to psychoneuroimmunology theory, the central nervous system (CNS), peripheral nervous system (PNS), endocrine system, and immune system are part of an intricate communication and feedback system. Any action that causes change or illness in one part of this system, such as the CNS, can potentially cause changes in the other parts of the psychoneuroimmunology system, such as endocrine or immune systems. Evidence suggesting that psychological stressors such as depression can alter immunological functions and possibly increase susceptibility to physical disease has accumulated over the past several decades .
Scores on the Beck Depression Inventory (BDI) were used to divide 40 non-hospitalized Caucasian women between the ages of 18 and 65 years into either the control or depression comparison group using psychoneuroimmunology theory and a descriptive comparison design.
Women with depression reported significantly more incidences of illness over the previous two months, and they had significantly more indicators of illness at the time of the exam as compared to the controls. Thus, this research suggests that depression may play a role in the subsequent development of minor acute infectious and inflammatory conditions as measured by outcomes on a brief physical exam.
However, contrary to what has been documented in some earlier research, women with depression in the current study did not have significantly different immune function measures as compared to the control group. There was also no significant correlation between scores on the BDI and natural killer cell cytotoxicity in this study.
While these results support a connection between depression and both increased self-report of illness and increased signs and symptoms of minor illness or inflammation on physical exam, this study did not find that these effects were related to decreased immune function as measured by natural killer cell activity or white blood cell counts.
However, researchers could not rule out the effect of depression on other immune system parameters, or the effect of depression on health outcomes via behavioral choices. Future research should include a wider variety of both behavioral measures and immune function outcomes to further delineate the effects of all of these factors on health outcomes in women with depression.
Material adapted by CFisher from:
Howk, C., & Bennet, M. (2010). Immune function and health outcomes in women with depression. BioPsychoSocial Medicine, 4:3.
 Kessler RC, Chiu W, Demler O, Walters EE: Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Arch Gen Psychiatry 2005 , 62(6):617-27.
 Glaser R: Stress-associated immune dysregulation and its importance for human health: a personal history of psychoneuroimmunology. Brain Behav Immun 2005 , 19(1):3-11.