Evidence is growing that people taking the common antidepressants known as selective serotonin reuptake inhibitors (SSRIs) may be at risk for thin bones, reports the Harvard Mental Health Letter. In the past few years, well-designed studies have not only built a case for a biological link between bone and the brain, but also suggested that SSRIs may be particularly harmful to bone. Researchers have identified several possible mechanisms linking brain and bone. Studies have reported that depression elevates levels of both the stress hormone cortisol and various immune system cells that promote inflammation—changes that can harm bone. More recently, scientists have discovered that bone cells have receptors for various brain chemicals and may be responsive to changes in the brain. For example, researchers have examined the impact of the mood hormone serotonin on bone health. SSRIs enhance serotonin activity by inhibiting a brain target known as 5-hydroxytryptamine (5-HTT). Investigators discovered that bone also has receptors for 5-HTT and wondered if SSRIs might therefore affect the bone. Laboratory research on this possibility has produced mixed results. Still, results from 4 of 5 epidemiological studies support the theory that SSRI use weakens bone and increases the chance of fracture—even after adjusting for other factors such as depression. Dr. Michael Miller, editor-in-chief of the Harvard Mental Health Letter, notes that many questions remain about the link between brain and bone. Notably, none of the research has involved children or adolescents. And current treatment guidelines for osteoporosis do not list SSRI use as a risk factor. But because the growing evidence suggests that SSRIs cause bone loss, it may make sense for clinicians and patients to discuss bone health along with mental health.
(Source: Harvard Mental Health Letter, August 2009)
