Research indicates that pre-menopausal women with depression have significantly lower bone mineral density (BMD) than pre-menopausal women without depression. Although the mechanisms of BMD loss are unclear, researchers believe that individuals with depression have impaired calcium absorption. However, it is unknown whether the abnormal absorption is a result of depression or a side effect of the drugs used to treat it. This study will compare calcium absorption in women with depression and in healthy women without depression.