Major depression, it appears, cannot only gnaw away at one’s happiness, but at one’s bones.

The first longitudinal study underscoring depression’s deleterious effects on bone density is reported in the January American Journal of Psychiatry by a group of German investigators. "The identification of depression as a risk factor for osteoporosis has important public health implications," they write, since 5 percent to 10 percent of any population succumbs to a major depression at some point.

The lead author of the study was Ulrich Schweiger, M.D., of the Medizinische Universität zu Lübeck. In 1994 Schweiger and his coworkers published the first cross-sectional study describing low bone density in depressed patients. This finding was confirmed by several other groups. However, it was possible that the subjects scrutinized in these studies already had low bone density before they developed depression. So the only way to ascertain whether depression really could lead to bone loss, Schweiger and his colleagues reasoned, was to conduct a longitudinal study.

With computerized tomography they measured bone density in 18 depressed male and female patients older than 40 years and in 21 healthy male and female controls. (Four of the women in the depression group and three of the women in the control group were postmenopausal, but none took estrogens or fluorides to prevent bone loss.) Two years later they measured the bone density of the 39 subjects again. Bone density at follow-up, the researchers found, was significantly lower in the depressed group than in the control group after adjusting for the effects of initial bone density, age, and gender.

An unexpected finding also emerged from the results: Depressed men had lost more bone than women had. While Schweiger could not explain that finding, he told Psychiatric News that he had two possible explanations. For one, perhaps depressed men in their study had been more despondent than the depressed women had been, and as a result, had experienced more dramatic bone loss. For another, perhaps women are better protected against depression-provoked bone loss than are men, at least before the onset of menopause. The researchers, however, did not examine their data to see whether they might have supported this explanation.

In any event, the important message of these findings for psychiatrists, other physicians, and the general public, Schweiger believes, is that depressed patients need not only psychiatric treatment but also established medications to prevent bone decline. He pointed out, however, that the early treatment of depression with antidepressants might also have a protective effect on bone density since antidepressants normalize the endocrine consequences of depression, and it is probably via hormones that depression harms bone metabolism.