Sleep dysfunction is common among patients with Parkinson's disease and occurs in approximately two thirds of patients. The problems range from nocturnal issues such as difficulty with sleep initiation, sleep fragmentation, disturbance of circadian rhythm, and rapid eye movement sleep behavior disorder, to daytime problems such as excessive daytime sleepiness. Frequent nighttime awakening and sleep disruption are the most common sleep problems in Parkinson's disease. Dopamine plays an important role in maintaining wakefulness. To improve sleep in Parkinson's disease, it is important to achieve the critical balance of adequate dopaminergic therapy and control of symptoms. Increased dopaminergic agents can cause dyskinesias and painful dystonia, and undertreatment can cause nighttime akinesia, rigidity, and worse quality of sleep. Other nondopaminergic drugs commonly used in Parkinson's disease can also affect sleep. In patients with advanced Parkinson's disease, deep brain stimulation of the subthalamic nucleus has a favorable impact on sleep quality and sleep architecture.

Although Parkinson's disease is defined by its motor symptoms, the symptoms that are most devastating to patients and caregivers are dementia and psychosis. In addition, sleep has a tremendous impact on patient well being and quality of life. Eighty percent to 90% of Parkinson's disease patients have a sleep disorder affecting their ability to fall asleep, ability to stay asleep, dreams, motor activity during sleep, post-sleep behavior, or day-time somnolence. Treatment plans for patients with Parkinson's disease who experience sleep disorders aim to improve nighttime sleep or daytime wakefulness, and treatment options vary by sleep disorder.

Psychosis in Parkinson's disease refers to a combination of hallucinations and delusions occurring with a clear sensorium and a chronic course. Hallucinations may involve several sensory modalities. Complex visual hallucinations are the most common type. “Minor” hallucinatory phenomena are frequently present and include visual illusions, passage hallucinations, and sense of presence. Insight may be lost in patients with cognitive impairment. Delusions of a paranoid type are more rare than hallucinations. Both hallucinations and delusions are more frequent in Parkinson's disease patients with dementia. Pathogenesis involves complex and probably multifactorial mechanisms, including pharmacologic (dopaminergic treatment and others) and disease-related factors.

It is essential to recognize and treat psychosis in Parkinson's disease for several reasons. Studies have shown that psychosis in Parkinson's disease patients is a strong risk factor for nursing home placement. Psychosis may be the greatest source of stress for caretakers of Parkinson's patients; it is often persistent, and its presence markedly increases mortality. Treatment of psychotic symptoms should occur only after potential medical and environmental causes of delirium have been eliminated or addressed. Initial pharmacologic changes should include limiting the patient's antiparkinsonian medications to those that are necessary to preserve motor function. Should that fail, an atypical antipsychotic is presently the treatment of choice. An emerging treatment option is acetylcholinesterase inhibitors. This article reviews what is currently known about the course, prognosis, and treatment strategies in Parkinson's disease psychosis.