Nonorganic hypersomnia - Epidemiology, diagnosis and treatment

Daytime tiredness and daytime sleepiness are frequent complaints occurring in 29% and 14% of the Austrian population. Epidemiological studies demonstr ate a high comorbidity between nonorganic hypersomnia and mental disorders. Especially comorbidity with affective disorders increases steadily from th e general population over primary to tertiary care settings. Diagnostic cri teria of nonorganic hypersomnia have been described in the International Cl assification of Diseases (ICD-10). Nonorganic hypersomnia can be primary or associated with a number of psychiatric disorders such as reaction to seve re stress or adjustment disorders, affective disorders, other functional di sorders, tolerance to or withdrawal of CNS-stimulating substances and chron ic use of CNS-sedating substances. Diagnostic procedures comprise case hist ory and symptom evaluation, sleep-specific and supplementary investigations . Concerning the latter, this article will focus on sleep questionnaires, v igilance and psychological tests as well as CNS investigations. Therapy of nonorganic hypersomnia rests on 3 pillars: psychological, somatic and pharm acological treatment. In view of the wide variety of psychiatric causes, re sulting in a number of therapeutic options, it seems desirable that apart f rom subjective clinical assessment also objective methods be used in diagno sis and treatment. On the neurophysiological level objective measures can b e obtained by means of EEG mapping during the day and polysomnography at ni ght. Different mental disorder patients show different brain activity patte rns as compared with normal controls and different classes of psychotropic substances cause different changes in neuro-physiological variables. The fa ct that the changes in electrophysiological brain activity caused by mental disorders are exactly opposite to those induced by the psychotropic drugs used for their treatment suggests a key-lock principle in the diagnosis and treatment of nonorganic hypersomnia.