O'Connor et al1 find that self-reported stress seems to increase breast milk secretory IgA levels, and success at relaxation was inversely related to secretory IgA levels in the group learning relaxation. They conclude that research would benefit from a biofeedback system capable of providing minute-to-minute evidence of immune status. The fact that delay-dependent speeding of reaction time, indicating motor readiness, is abolished by depletion of dopamine associated with certain immune functions, cortical silent periods, highlighting of significant stimuli, regulation of the microvasculature and splanchnic blood flow, and mood2- 7 prompts future research on the effect of stress on the immune system1 by monitoring temporal features of expressive activity in spontaneous dialogues.
Friedman E. Relaxation Training and Levels of Secretory IgA in Breast Milk. Arch Pediatr Adolesc Med. 1999;153(6):654-655. doi: