Premenopausal women with even mild depression have less bone mass than do their nondepressed peers, say researchers in the Nov. 26 issue of Archives of Internal Medicine.
The study included 89 women with mild depression (test group) and 44 women without depression (control group). All participants were between 21 and 45 years old and pre-menopausal. Except for depression, the two groups were similar in risk factors, including calcium, caffeine and alcohol intake; smoking status; level of physical fitness; use of oral contraceptives; and age of first menstrual period. Women in both groups were of relatively high socioeconomic status and well-nourished. The women in the test group were having or recently had had a depressive episode, and they were taking antidepressant medications.
Researchers found that 17 percent of the women in the test group had thinner bone in a vulnerable part of the hip called the femoral neck, compared with 2 percent of those in the control group. They also found low bone mass in the lumbar spine in 20 percent of the women in the test group and 9 percent of the women in the control group. This level of bone loss is at least as high as that associated with recognized risk factors for osteoporosis, including smoking, low calcium intake and lack of physical activity.
Researchers found no significant link between the degree of bone loss and the severity of depression or the cumulative number of depressive episodes.
Test results from blood and urine samples showed that women in the test group had imbalances in immune-system substances, including those that produce inflammation, compared with those in the control group. The immune-system imbalances may be tied to excess adrenalin, since the part of the nervous system that produces adrenalin is overactive in depressed people. Increased adrenalin can overstimulate the immune system.
Compared with the control group, the women in the test group had higher levels of immune-system proteins that promote inflammation and lower levels of those that prevent it. One of these inflammation-promoting proteins, interleukin 6 (IL-6), promotes bone loss. At the molecular level, bones routinely break down, and minerals such as calcium are reabsorbed into the blood where they travel throughout the body to perform crucial functions in cells. At the same time, the body builds the bone back up. Imbalances in this normal loop of bone re-absorption and build-up, such as high levels of IL-6, could promote bone loss, the researchers suggested.
"Depression generally isn’t on clinicians’ radar screens as a major risk factor for osteoporosis, particularly for pre-menopausal women, and it should be," said study co-author Giovanni Cizza, MD, PhD, MHSc, senior investigator, Clinical Endocrinology Branch, National Institute of Diabetes & Digestive & Kidney Diseases.
This study was funded, in part, by the National Institutes of Health National Institute of Mental Health.
