The immunoregulatory effects of antidepressants

Abstract There is some evidence that major depression is accompanied by activation of the inflammatory‐response system (IRS). It has been hypothesized that increased production of proinflammatory cytokines may play a role in the etiology of major depression. If increased production of proinflammatory cytokines is at all involved in the etiology of depression, one would expect antidepressive treatments to have negative immunoregulatory effects. This paper reviews the effects of antidepressants, such as tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), heterocyclic antidepressants (HCAs), serotonin‐noradrenaline reuptake inhibitors (SNRIs), lithium, l ‐5‐hydroxytroptophan (L‐5‐HTP), reversible inhibitors of MAO‐A (RIMA) on the production of proinflammatory cytokines, e.g. interferon‐γ (IFNγ), and negative immunoregulatory cytokines and agents, e.g. interleukin‐10 (IL‐10). In depressed patients, prolonged treatment with antidepressants and mood stabilizers normalizes signs of activation of the IRS, such as increased serum IL‐6 and acute phase protein concentrations. In vitro, it has been shown that various types of antidepressive drugs, including TCAs (imipramine; clomipramine); SSRIs (citalopram, fluoxetine, sertraline); lithium; SNRIs (venlafaxine); HCAs (trazodone); RIMAs (moclobemide) and L‐5‐HTP significantly suppress the ratio of IFNγ/IL‐10 production by peripheral blood immunocytes. These antidepressant drugs appear to have a common effect on the IRS, i.e. in vitro they increase the production of IL‐10 by peripheral blood leukocytes. Thus, the results suggest that antidepressants have negative immunoregulatory effects. It may be speculated that antidepressants exert some of their antidepressant effects through their negative immunoregulatory capacities. Copyright © 2001 John Wiley & Sons, Ltd.