[The incubus phenomenon: A sleep-related condition, not to be confused with psychosis]

The incubus phenomenon is a paroxysmal condition characterised by sleep paralysis coinciding with a sensed presence and the frightening sensation that something or somebody is exerting pressure on the thorax.To present an overview of the literature on the incubus phenomenon and to provide practical advice regarding diagnosis and treatment.To obtain information for our paper we carried out a search in PubMed and the historical literature.The incubus phenomenon is a relatively unknown condition, even though, world-wide, it has a lifetime prevalence rate of 30% in the general population. The prevalence is even higher among students, psychiatric patients and patients with narcolepsy. It is attributed to a dissociation of the rem sleep phase and the subsequent intrusion of endogenously mediated percepts. The condition rarely requires treatment because it is self-limiting, and generally occurs only once in a lifetime. Repeated attacks, however, may warrant additional diagnostic testing with the aid of polysomnography and may require treatment with anxiolytics, antidepressants, anticholinergics or anti-epileptics.The incubus phenomenon is an intrusive condition, but, as far as we currently know, it is benign. Nevertheless, it is important that the condition is recognised and not confused with a psychotic disorder or any other type of severe mental illness. When necessary, it should be treated lege artis.