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There's no apparent connection between depression and osteoporosis. But researchers at the Hebrew University of Jerusalem have found that depression can cause a loss of bone mass.
They say their findings constitute a significant step forward in understanding how the mind and the skeletal system interact and have already demonstrated the efficacy of antidepressant drugs in preventing bone mass loss. The researchers findings have just been published in the the prestigious American journal PNAS (Proceedings of the National Academy of Sciences).
Loss of bone mass is the leading cause of osteoporosis and bone fractures among the aged in general and among post-menopausal women in particular. Several studies indicate that people suffering major depression generally have lower than average bone mass density, but until now, no direct link between these two conditions has been established.
The project was conducted by researchers from HU's brain and behavior laboratory headed by Prof. Raz Yirmia; from the bone lab headed by Prof. Itai Bab; and from the brain trauma lab headed by Prof. Esther Shohami. Also participating were doctoral students Inbal Goshen, Alon Bajayo, Tirza Kreisel, Sharon Feldman and Yosef Tam.
They used mice to study the connection between depression and bone mass loss. After inducing a depressionlike condition in the rodents, they developed behavioral symptoms mirroring those seen in depressed humans, including a reduction in pleasurable activity and in social interaction. After four weeks in a depressed state, the mice showed a dramatic bone mass loss, including in the hip bone and vertebrae.
This loss was caused by impairment in the bone renewal process, which is essential to maintaining normal bone density. The impairment was caused by a reduction in the number of bone-building cells, which are called osteoblasts.
Tests showed that chronic use of an antidepressant drug halted not only the depression itself but also the loss of bone density.
The researchers were also able to describe the process linking depression to the skeletal structure. They found that depression sets off a neural system connecting the brain to the internal organs, including the skeleton. This system is called the sympathetic nervous system, and its activation causes the secretion within the bone of noradrenaline, a chemical that has a detrimental effect on the bone-building cells. The researchers were able to show that chronic treatment with a drug that blocks noradrenaline in the bone also blocks the detrimental influence of depression on the bone.
The research is expected to serve as the basis for new, efficient drugs for treatment of osteoporosis, which is the most prevalent degenerative disease in western society. The HU's technology transfer company, Yissum, has applied for a patent for treatment of osteoporosis with antidepressants.
"The connection between the brain and the skeleton in general, and the influence of depression on bone mass in particular is a new area of research about which we still know very little," said Yirmiya. "The new findings, which we have discovered in HU labs point for the first time to depression as an important element in causing bone mass loss and osteoporosis."
Bab said, "Together with other research that we have published in the past year, we have developed a new area of research that we call 'neuropsycho-osteologyâ€š' which deals with the connection between the brain, mental states and the skeleton."