Parkinson's disease (PD) is traditionally regarded as a motor or a movement disorder. In recent years, however, an increase interest has been directed to its nonmotor symptoms as they seem to determine significant disability at all stages of the disease. Among these nonmotor symptoms, neuropsychiatric syndromes (or behavioral and psychological symptoms) are of paramount importance. They include a wide array of syndromes, such as anxiety, depression, psychosis, impulse control disorders, and apathy, that represent a challenge in the management of PD patients.

We take interest in all manuscripts that report the epidemiology of these neuropsychiatric syndromes in clinical and community settings, their impact on clinical management and quality of life, their neurobiological basis, and their therapeutic approaches. Papers dealing with clinical criteria of specific neuropsychiatric syndromes in PD are also welcome. The intention of the present issue is to become an international forum for researches to report original data and to summarize the most recent development on the neuropsychiatry of PD. Potential topics include, but are not limited to:

• Clinical criteria for different neuropsychiatric syndromes in PD
• Epidemiology of different neuropsychiatric syndromes in PD
• Impact of neuropsychiatric syndromes on morbidity and mortality of PD patients
• Neurobiological mechanisms and correlates of neuropsychiatric syndromes in PD
• Biomarkers of neuropsychiatric syndromes in PD
• Structural and functional neuroimaging in PD
• Pharmacological therapeutics to specific neuropsychiatric syndromes in PD
• Nonpharmacological approaches to neuropsychiatric syndromes in PD, including deep brain stimulation and transcranial magnetic stimulation