This study rules out the use of SSRIs as a cause of osteoporosis, but suggests that an imbalance in the immune or inflammatory systems in women with depression may be to blame.
For the study, rate of bone loss was examined using X-ray absorptiometry in 89 women who had been diagnosed with mild depression, or had recently suffered a depressive episode, and 44 women without depression. All were aged 21 to 45.
The two groups were similar for all other osteoporosis risk factors. Over the course of the two year study, researchers found that 17 per cent of depressed women had thinner bone in a vulnerable part of the hip, the femoral neck, compared with only 2 per cent of those without depression.
Low bone mass in the lumbar spine was found in 20 per cent of depressed women, but in only 9 per cent of the control group.
No significant link was seen between the degree of bone loss and the severity of depression.
Blood and urine samples revealed that depressed women had higher concentrations of proinflammatory cytokines and tumour necrosis factor alpha and lower levels of anti-inflammatory factor IL-13, compared with healthy women.
Researchers propose that the imbalances in the levels of inflammatory substances may cause osteoporosis in depressed women.
Lead researcher Dr Giovanni Cizza, from the US National Institute of Mental Health, said: 'Depression is not on doctors' radar as a major risk factor for osteoporosis, particularly for premenopausal women.
'We know that depression can be a red flag, that depressed women are more likely than other women to approach menopause with a higher risk of fractures.'
Arch Intern Med 2007; 167: 2,329-36
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