Depression[1] is well recognized in PD, having been identified as "melancholia" by James Parkinson in his original report of the disease in 1817. Estimated prevalence rates of depression vary widely according to the population sampled and methodology used, although depressive symptoms, irrespective of classically defined DSM criteria for depression, are present in 35% of patients[13] There is an increased risk for any individual with depression to go on to develop Parkinson's disease at a later date.[14][15][16] It is increasingly thought to be a consequence of the disease rather than an emotional reaction to disability, although ample evidence shows that the relationship between depression and PD is bidirectional.[17][18] General risk factors for depression are actually stronger markers for depression in PD patients than PD specific factors.[19] Since Parkinson's affects many areas of the brain that control mood (specifically the frontal lobe as well as those areas that produce serotonin, norepinephrine and dopamine), depression may result.[20] Depression is one of the most common neuropsychiatric conditions found in patients who have PD, and it is associated with more rapid progression of physical symptoms and a greater decline in cognitive skills.