Depression and anxiety in Parkinson's disease

Parkinson's disease (PD) is accompanied by nonmotor symptoms (NMS) such as mood disorders. Among them, depression and anxiety complicate PD and are present at high rates in PD patients. Organic depression is generally known to affect a patient's recovery from the sequelae of the primary disease; thus early detection and appropriate treatment are essential. Depression in PD is thought to result from different factors such as disappearance of neurons in the dopamine, noradrenaline, and serotonin as well as from psychogenic reactions associated with the onset of the disease. Moreover, anxiety may also be a side effect of PD treatment. As morbid states of depression and anxiety are complicated, these symptoms are often difficult to diagnose. Moreover, the validity of these diagnostic methods has not been established. Therefore, accurate diagnoses of morbid states in the early stage of the disease and corresponding appropriate treatments are vital.