ObjectiveThe goal of this study was to investigate whether clinical insomnia is associated with immune alterations by comparing immune functioning between patients with chronic insomnia and good sleepers.MethodsThe good sleepers group was composed of 19 adults with a regular sleep schedule and no complaint of sleep disturbances. The insomnia group was composed of 17 adults meeting criteria for a chronic primary insomnia disorder. Peripheral blood samples were taken at the interview (time 1) and before the second night of polysomnographic assessment (time 2) for immune measures, including enumeration of blood cell counts (ie, white blood cells, monocytes, lymphocytes, and CD3+, CD4+, CD8+, and CD16+/CD56+ cells), natural killer cell activity, and cytokine production (ie, interleukin-1&bgr;, interleukin-2, and interferon gamma).ResultsSignificant between-group differences were observed for CD3+, CD4+, and CD8+ cells, with higher levels found in good sleepers. In addition, a significant group-by-time interaction was found on monocyte counts. Although this was the only significant interaction effect observed, between-group differences were greater at time 2.ConclusionsThis study suggests that chronic insomnia is associated with some immune alterations. More research is needed to determine the clinical significance of these findings.