The level of bone density loss attributed to depression in the study was similar to that previously associated with other well- known osteoporosis risk factors, including smoking cigarettes and getting little or no exercise.
The average age of the women in the study was 35 and none had reached menopause.
"The question of whether depression is associated with osteoporosis had not really been addressed in younger women," researcher Giovanni Cizza, MD, PhD, of the National Institute of Mental Health (NIMH) tells WebMD.
Depression and Bone Loss
Earlier research suggested a link between depression and bone density loss in older women, and a study published earlier this year found that use of selective serotonin reuptake inhibitor (SSRI) antidepressants may exacerbate bone thinning in older women.
The newly published study, published today in the Archives of Internal Medicine, included 89 women with mostly mild depression between the ages of 21 and 45 and 44 similarly-aged women without depression.
Except for depression, the women in the two groups had similar risk factors for osteoporosis.
Bone mineral density testing revealed that 17% of the depressed women showed evidence of bone thinning at a particularly vulnerable area of the thigh bone, compared to 2% of women who were not depressed.
Lower bone density at the lumbar spine was also seen in 20% of the depressed women, compared to 9% of women without depression.
Cizza says depression was associated with a 2% reduction in bone mass at the hip -- roughly seven times the expected loss for a healthy premenopausal woman and comparable to the accelerated loss seen each year in the first few years following menopause.
Other risk factors for bone loss, like low calcium intake, cigarette smoking, and lack of exercise did not explain the difference in outcomes. And a subanalysis of patients taking antidepressants suggested that the medications were not a factor in the bone loss.
"This study shows that even mild depression can have very real consequences for bones," Cizza tells WebMD. "Depression needs to be recognized as a risk factor for bone loss in premenopausal women and general practitioners should consider testing women with depression for osteoporosis and treating them if necessary."
Hormones and Bones
It has been suggested that specific hormonal changes associated with depression lead to bone loss, and the study strengthens the case for the link.
Study participants with depression had much higher blood levels of inflammatory proteins secreted by the immune system than the participants without depression and much lower levels of anti-inflammatory proteins.
An inflammatory protein that has specifically been linked to bone loss -- interleukin-6 -- was found to be significantly elevated in the women with depression, compared to women without depression.
Ten million older Americans have osteoporosis, and an estimated 1.5 million experience fractures related to osteoporosis every year.
Because early osteoporosis is primarily a silent disease, knowing that even mild depression can lead to bone loss years before fractures occur is of major clinical importance, NIMH deputy director Richard Nakamura, PhD, said in a press statement.
"Too often, the first symptom a clinician sees is when a patient shows up with a broken bone," he notes. "Now we know that depression can serve as a red flag -- that depressed women are more likely than other women to approach menopause already at higher risk of fractures."