Tentative classification of neuropsychiatric disturbances in Prader-Willi syndrome.

Prader-Willi syndrome presents behavioural characteristics at the temperamental level which can be described as oppositional, explosive and at times antisocial. These traits may fluctuate and be driven by unknown biological anxiety symptoms are also frequent. Delusional psychotic thinking is manifest in some cases, but may be latent in several such patients. A third set of manifestations is a 'refusal-lethargy' syndrome of akinesis, refusal of food and drink, and soiling, which seems to be triggered by environmental circumstances but resembles the hypersomnic, lethargic depressions. These three sets of phenomena are documented through the clinical observation of nine cases and may be useful in the study of the genotype-phenotype relationship in this and other syndromes, particularly those in which similar manifestations are observed and cyclic changes are seen. The use of drugs in this syndrome can also become more rational if this classification is used to identify clearer targets for treatment. The possibility that most manifestations of the syndrome may be an expression of a hyposerotonergic defect is suggested.