Clinical depression is one of the most common medical problems. Approximately 8% of men and 16% of women will experience an episode of major depression during their lifetime. Depression is a serious problem that can dramatically decrease quality of life, functioning at work and home and, when serious, can increase risk of suicide. PTSD sufferers seem to be at a much greater risk for developing depression--over 59% of veterans with PTSD also had depression, as well as 53% of those whose PTSD was caused by an automobile accident. Fortunately, the selective serotonin reuptake inhibitors (SSRIs) that treat PTSD are also effective for depression.

Depression is not just a problem of low mood. Many people who have depression find that loss of interest in usually enjoyable activities is the prominent feature. Other common problems are difficulty with sleep (too little or too much), change in appetite, fatigue, difficulty concentrating, anxiety, thoughts of death and low self-esteem.