In Brief

Keep a close eye on granny's mental health: A new study shows that even mild chronic depression may affect her ability to fight off infections and cancer. The study, published in the January Journal of Abnormal Psychology (Vol. 111, No. 1) finds that sub-clinical chronic depression is linked to a slower immune response in older adults.

Lead researcher Lynanne McGuire, PhD, now at Johns Hopkins School of Medicine, and Janice K. Kiecolt-Glaser, PhD, and Ronald Glaser, PhD, of the Ohio State University College of Medicine recruited adults from a larger longitudinal study on stress and health in older adults. Of the 78 participants--who had an average age of 72.5 years--slightly more than half were spousal caregivers for dementia patients and the rest were non-caregivers who were controls in the larger study. The researchers looked at their symptoms of depression and their white blood cell counts, which provide a model of the body's response to infectious agents.

They found that only 22 of the 78 participants showed signs of depression. In fact, fewer than half of those 22 met the formal criteria to diagnose depression. But they all showed a diminished immune response--an especially serious result in older adults.

Indeed, the authors found that the combination of mild depression and the normal effects of aging create an even slower immune system response than either factor does individually. However, the researchers note that participants in this study were selected for "presence or absence of chronic depressive symptoms" and the results might not be the same in adults with more severe or episodic symptoms of depression.

McGuire and her colleagues suggest that in order to maintain the highest level of immune function in older adults, health-care professionals must track even subclinical depression. They say their research shows that "failure to address chronic, mild depressive symptoms in older adults has important negative physiological consequences."