background   There is considerable evidence to support the notion that mood disturbances, stressful life events, and psychiatric disorders are closely connected with the neuroendocrine and immune systems. Increasing interest is being shown in the role that cytokines play in these interactions.
aim   An attempt is made to cast light on the modulating function of cytokines in the pathophysiology of major depression.
method   Pubmed was used to review the literature published between 1980-2004 on the basis of the key words 'cytokines', 'depression', 'stress' and 'interleukins'. Additional information was obtained via the bibliographic references attached to the articles concerned.
results   In depressed patients a combined dysfunction of the immune system, serotonin turnover and the hypothalamic-pituitary adrenal axis seems to form part of the etiology of depression.
conclusion   This model, which associates depression with the immune system, can explain both the organic etiology (internal stressors) and the psychosocial etiology (external stressors) of major depression; both types of stressors cause depression by activating the immune system and increasing the release of pro-inflammatory cytokines.