Group items tagged

The phenomenon arises just prior to falling asleep or on awakening (ASDA, 1990; Takeuchi, Fukuda, Sasaki, Inugami, & Murphy, 2002) and is often accompanied by hypnagogic (sleep-onset) or hypnopompic (sleep-offset) hallucinations. Sleep paralysis can also affect individuals without excessive daytime sleepiness or cataplexy—that is, without a diagnosis of narcolepsy—and is referred to in those cases as isolated sleep paralysis (ISP; ASDA, 1990; Fukuda, 1994; Hishikawa & Shimizu, 1995; Takeuchi, Miyasita, Sasaki, Inugami, & Fukuda, 1992)

HHs to be vivid auditory, tactile, or kinesthetic images most often associated with fear, terror, or dread.

PRES occurring with ISP tends to be associated with fear as well as with visual and, less often, auditory hallucinations; together, these components constitute a particular type of HH referred to as the “intruder” (Cheyne, 2001; Cheyne, Rueffer, & Newby-Clark, 1999).

The hallucinated presence, in turn, triggers intense fear, which leads to a brief search for signs of danger to corroborate the feeling of presence.

Apart from some work assessing panic disorder among African American samples, few studies have systematically investigated possible links between anxiety and ISP (with associated HHs).

An early study by Bell et al. (1986) revealed that 15.5% of subjects with ISP also had panic disorder. However, only 25 subjects participated in this study, and no controls were assessed.

Another study revealed that 7 out of 18 African Americans diagnosed with panic disorder and hypertension also had ISP (Neal, Rich, & Smucker, 1994). Unfortunately, the prevalence of ISP among hypertensives without panic disorder was not assessed.

The fact that PRES is the most prevalent form of HH and is frequently associated with fear is consistent with the possibility that the individual experiencing it may be frightened by the presence of others in a more general sense. In this respect, ISP with PRES shares many commonalities with social anxiety, which is a marked and persistent fear of social situations involving unfamiliar people or scrutiny by others

Third, evidence from neurobiology supports a hypothesized link between the HHs accompanying ISP and social anxiety. A recent study using the positron emission tomography technique found an overactivation of the amygdala among socially anxious subjects while they spoke in public (Tillfors et al., 2001). Consistent with this, it has been proposed that intruder hallucinations might be associated with increased activity in the amygdala (Cheyne, 2001; Cheyne, Rueffer, & Newby-Clark, 1999).

Fear, visual imagery, and PRES might constitute a constellation of cognitive-emotional processes also common to socially anxious individuals.

“the presence is watching or monitoring the subject.”