Immunity in young adults with major depressive disorder

Objective: The authors previously found evidence for an age-related association between major depression and altered immunity. The present study was designed to assess a range of immune measures in young adults with major depression. Method: A homogeneous group of 21 unmedicated, ambulatory young adults with unipolar major depressive episode, as determined with the Structured Clinical Interview for DSM-III-R, were assessed in comparison with 21 matched nondepressed subjects. An extended battery of quantitative and functional immune measures was obtained on the same day from depressed and nondepressed subjects. Results: Young adult subjects with major depression had more circulating leukocytes and granulocytes, fewer CD56+ (natural killer [NK]) cells, and, when the number of circulating NK cells was controlled, less NK cell activity. Mitogen responses, consistent with the authors' previous report, showed little difference between the young adults with and without major depression except for a possibly greater response at the highest dose of phytohemagglutinin. Conclusions: Major depression in young adults is associated with alterations in aspects of the immune system primarily involving NK cells. Some but not all of these immune changes differ from those found in older depressed adults.