It is thought that most PD patients develop depressive symptoms of some duration, and that depression is associated
with the disease. Depression in PD is similar to that in the general population; but with a higher incidence of feelings
of failure, anxiety, and suicide , and a decreased incidence of feelings of guilt and self-blame. Many patients with PD
find secondary symptoms, including depression, to be more troublesome than the characteristic motor symptoms.
Diagnosis of depression in PD is based on presenting psychological symptoms; patients with PD may be diagnosed
with major depressive disorder, seasonal affective disorder, dysthymic disorder, or minor depression. Assessment for
and diagnosis of depression in patients with PD may be complicated by the fact that some symptoms of PD overlap
with those of depression (e.g., insomnia, fatigue, difficulty concentrating).