The relationship between chronic pain, immune function, depression, and health behaviors

The objectives of this study were 1) to determine the relationships between pain perceptions, immune function, depression and health behaviors and 2) to examine the effects of chronic pain on immune function using depression and health behaviors as covariates. A nonexperimental cross-sectional design was used to compare 24 chronic back pain patients with 33 asymptomatic no-pain healthy subjects. Immune function measures using natural killer (NK) cell activity, percent and numbers of NK cells, and T-cell lymphocyte proliferation with mitogens concanavalin A (ConA) and pytohemagglutinin (PHA) as well as self-report measures for depression and health behaviors were collected on all subjects. Pain perceptions showed positive significant correlations with depression (P = 0.01) and total percent of NK cells (P = 0.04). Depression and health behaviors were negatively correlated (P = 0.01). Positive associations were observed for depression and 2 PHA mitogen levels (P < 0.05). Comparison of group means, controlling for depression and health behaviors, showed that chronic pain patients' immune function, as measured by the combined NK effector to target (E:T) cell ratio levels, was significantly higher than the no-pain comparison group. Pain perceptions may have a deleterious effect on enumerative NK cell measures and depression levels. However, people with chronic pain may not experience attenuation in functional immune parameters.