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Lymphocyte subsets associated with major depression and dysthymia: modification by antidepressant treatment

A V Ravindran1, J Griffiths, Z Merali

  • 1Department of Psychiatry, University of Ottawa, Ontario, Canada.

Psychosomatic Medicine
|November 1, 1995
PubMed

Insights

Major depression and chronic depression (dysthymia) show increased natural killer (NK) cells. Treatment with serotonin reuptake inhibitors normalized NK cell counts, suggesting a link between depression, stress, and immune function.

Area of Science:

  • Immunopsychiatry
  • Neuroimmunology
  • Cellular Immunology

Background:

  • Major depression and dysthymia are mood disorders associated with significant psychological distress.
  • Previous research suggests a complex interplay between the central nervous system and the immune system in psychiatric conditions.
  • Lymphocyte subsets, including natural killer (NK) cells, are key components of the immune system that may be affected by depression.

Purpose of the Study:

  • To investigate the association between major depression and dysthymia and specific lymphocyte subsets, particularly natural killer (NK) cells.
  • To examine the impact of selective serotonin reuptake inhibitor (SSRI) treatment on NK cell numbers in depressed patients.
  • To explore correlations between stress-related hormones and lymphocyte subsets in different depression subtypes.

Main Methods:

  • Blood samples were analyzed for lymphocyte subsets, including CD16/56 (NK) cells, CD3, CD4, CD8, and CD19.
  • Patients with major depression and dysthymia were treated with SSRIs, and changes in NK cell numbers were monitored.
  • Plasma levels of epinephrine, norepinephrine, cortisol, and ACTH were measured and correlated with immune parameters.

Main Results:

  • Patients with major depression and dysthymia exhibited elevated numbers of CD16/56 (NK) cells compared to controls.
  • SSRI treatment led to a decrease in NK cell numbers, normalizing them to control levels.
  • NK cell normalization occurred within 4 weeks for major depression and 6 months for dysthymia.
  • Correlations between hormones (ACTH, epinephrine, norepinephrine) and lymphocyte subsets varied between patient groups.

Conclusions:

  • Increased NK cell counts are associated with both major depression and dysthymia.
  • SSRI treatment effectively reduces NK cell numbers in depressed individuals, indicating a reversible immune alteration.
  • The differential time course for NK cell normalization suggests distinct pathophysiological mechanisms or stress perception in major depression versus dysthymia.

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