<unk> , as developed in the 19th century, used primarily three categories: Insomnia, Hypersomnia and Nightmare. In the 20th century, increasingly in the last half of it, technological discoveries led to rapid advances in the understanding of sleep and recognition of sleep<unk> . Major sleep<unk>  were defined following the development of Electroencephalography (EEG) in 1924 by Hans Berger. Three systems of<unk>  are in use worldwide: * the International<unk>  of diseases (ICD) developed by the World Health Organization (WHO) and intended for use by general and more specialized practitioners, * the Diagnostic and Statistical Manual (DSM) from the American Psychiatric Association (APA) for psychiatrists and general practitioners, and * the International<unk>  (ICSD), an advanced system cultured by the American Academy of Sleep Medicine (AASM) for sleep specialists. The ICD and DSM lump different<unk>  together while the ICSD tends to split related<unk>  into multiple discrete categories. There has, over the last 60 years, occurred a slow confluence of the three systems of<unk> . Diagnoses of sleep<unk>  are based on self-assessment questionnaires, clinical interview, physical examination and laboratory procedures. The validity and reliability of various sleep<unk>  are yet to be proved and need further research within the ever-changing field of "Sleep Medicine". Admittedly, the development of sleep<unk> unk>  remains as much an art as it is a science.
Classification of sleep disorders
Cognitive neuroscience of dreams
Eating recovery
Sleep emailing
Sleep epidemiology
Assessment of suicide risk
Prognosis of schizophrenia
General movements assessment