Apathy and fatigue, sexual disturbances, mania, sleep disturbances, personality changes, pathologic gambling, and addiction to antiparkinson agents occur in patients with PD and may pose considerable stress on the patients themselves and their caregivers. With the exception of apathy and fatigue, little is known regarding the prevalence of these symptoms in patients with PD. The pathophysiologic mechanisms are unknown, although disturbances of the mesolimbic and mesocortical dopaminergic pathways are probably involved. Antiparkinsonian drugs or surgery seem to be the main etiologic factors for sexual disturbance, hypomania, addiction, and pathologic gambling, whereas hypodopaminergic states may contribute to symptoms such as apathy, fatigue, RBD, and possibly personality changes. Although some placebo-controlled trials have been published recently, no established treatments are currently available for these symptoms (85) (see Table 5-2), and thus future clinical trials are needed.