Osteoporosis and major depression: open debate on a bidirectional relationship

Osteoporosis and depression are two chronic diseases that affect large population groups with great impact on morbidity, mortality and quality of life. Existing studies of the relationship between depression and osteoporosis have been heterogeneous in their design and use of diagnostic instruments for depression, which might have contributed to the different results on the comorbidity of these two conditions. Moreover, the direction of the causative link is still controversial and the etiology remains unclear. Definitely, limited data suggest that osteoporosis may enhance depressive symptoms, while far more studies have shown that depression adversely affects bone density and increases fracture risk. Thus the correlation of these diseases is still under research. This review comments on a plausible causative relationship and underlying mechanisms that might elucidate the link between two very common diseases. We describe the possible impact of osteoporosis on moods and the effect of depression on bone health. In particular, we focus on the role of the hypothalamic-pituitary-adreno-cortical and sympathoadrenal axes, of the parathyroid hormone and cytokines. We also describe the effect of the antidepressant drugs as well as lifestyles that may explain this effect.