Research Item – Jean-Christophe Terrillon, PhD, and Sirley Marques‐Bonham, PhD
Isolated sleep paralysis (ISP) is a poorly understood phenomenon that has attracted increased attention in recent years both in the medical community (M. Dahlitz & JD Parkes, 1993 , Y. Hishikawa & T. Shimizu, 1995 ) and in psychological research (Fukuda et al., 1987-1994 [3-6], Wing et al., 1994 ). Although the occurrence of ISP is relatively common, recurrent ISP (RISP) is a rarer variant of sleep paralysis characterized by frequent episodes or a complex of sequential episodes whose total duration may exceed one hour, and particularly by the range and sense of perceived reality of the subjective phenomena experienced during episodes. Although such phenomena are usually categorized as hypnagogic or hypnopompic hallucinations, there is at present no integrated model that adequately explains the ensemble of physiological, neurological, cognitive and psychological components of RISP. As researchers who experience RISP, in this paper we attempt to synthesize information on RISP gathered from various sources and to conjecture possible connections between RISP and other as yet poorly understood phenomena at different levels: at a neurophysiological level, with anxiety disorders (A.S. Suarez, 1991 , C.M. Paradis et al., 1997 ), the Periodic Paralyses (R.E. Stedwell et al., 1992  ), and with Sudden Unexplained Nocturnal Death Syndrome (SUNDS) (S. Nimmanit et al., 1991 , B.B. Randall, 1992 , S.R. Adler, 1995 ); at a neurocognitive level, with lucid dreaming (S. Laberge, 1985 ); and finally, at a level that examines the possibility of the manifestation of paranormal phenomena during RISP episodes, with Out-of-Body Experiences (OBE) (C.T. Tart,1968 , K. Osis, 1981 ) and with Near-Death-Experiences (NDE) (R.A Moody, 1976 , K. Ring, 1979 ). Finally, we performed a statistical analysis on RISP by use of a sample of 250 direct or indirect respondents to a message posted initially by one of the authors on the sleep web site of the University of California in Los Angeles (UCLA) . Preliminary results indicate that over 90% of respondents experience intense fear during their RISP episodes, about 50% have invoked a paranormal or supernatural explanation, and that a typical RISP episode may be described as consisting of three main phases. We conclude with a brief description of possible strategies to cope with RISP.