Hypnotic Susceptibility, Dissociation, and Marijuana Use: a Relationship between High Hypnotic Susceptibility, Marijuana Use, and Dissociative Ability

Participants were 413 introductory psychology students from West Chester University. Participants completed the AnomalousExperiences Inventory (AEI) (Kumar, Pekala, & Gallagher, 1994) and the Dissociative Experiences Scale (DES) (Bernstein &Putnam, 1986). Participants then experienced the Harvard Group Scale of Hypnotic Susceptibility (Shor & Orne, 1962). Participants were divided into five groups of low to high susceptible participants (based on their responses to the Harvard) and ANOVA analyses were performed for the AEI drug items (use of alcohol, LSD, cocaine, heroin, and marijuana) as a function of hypnotizability and dissociative ability. A significant interaction between drug use and hypnotizability as a function of dissociative ability was found only for the use of marijuana. For participants who were highly hypnotizable (Harvard Scale scores of 10 to 12), endorsement of having used marijuana was associated with .significantly higher DES scores of about 1 SD in comparison to those participants who did not use marijuana. The interrelationships among dissociation, marijuana use, and hypnotizability are reviewed with reference to the above research findings. Pending replication, implications concerning the use of marijuana as a means for experimentally assessing dissociative processes are discussed. This paper first reviews current theorizing on the interrelationships among dissociation, the limbic system, marijuana intoxification, and hypnotizability and then delineates 112 a research protocol that fortuitously discovered an interesting relationship between marijuana use, high hypnotizability, and dissociation that, pending replication, may have relevance for understanding the dissociative disorders. DISSOCIATION AND THE LIMBIC SYSTEM Multiple memory systems have been postulated for some time now (Tulving, 1972). The term, "multiple memory system, " refers " to the idea that two or more (memory) systems are characterized by fundamentally different rules of operation" (Sherry & Schacter, 1987, p. 440). Tulving (1987) has proposed a three-tiered system involving procedural memory, semantic memory, and episodic memory. Procedural memory is action-based knowledge that refers to "knowing how," while semantic (general knowledge) and episodic memory (personal experiences) refer to "knowing that." Although controversial (Wilhite & Payne, 1992) , research by several investigators has suggested the functional dissociation of various memory systems (McDonald & White, 1993; Wilhite & Payne, 1992). Kihlstrom (1980) demonstrated a dissociation between semantic and episodic tasks as a function of hypnotic susceptibility level. Specifically, he found "the hypnotizability of the participants (being) strongly associated with performance on the episodic but not on the semantic task" (1980, p. 234). McDonald and White (1993) postulated a physiological basis for the separation of memory systems. They suggested that: a) "a normal hippocampus appears to be necessary for tasks that require the use of information about relationships among stimuli" (1993, p. 3), b) the amygdala may mediate the rapid acquisition of behaviors based on biologically significant events with affective properties" (p. 3), and c) the dorsal striatum "may mediate the formation of reinforced stimulus-response associations" (p . 3 ) . MARIJUANA, MEMORY, AND THE LIMBIC SYSTEM Cannabis intoxification has been implicated in the manifestation of dissociation. Marijuana has been found to affect short-term memory in clinical participants (Schwartz, 1991). Not only is there an immediate decrement in short-term memory, but this recent memory decrement can have more longDISSOCIATION, Vol. 1 III. No. 2, June 1995 PEKALA/KUMAR/MARCANO term effects. Its continuation is dependent on the amount of tetrahydrocannabinol (THC) in the limbic system. Essman (1984) made a distinction between the immediate decrements in short-term memory from acute marijuana intoxification and a "retroactive memory impairment apparently resulting from the disruption by marijuana or one of its constituents of memory-trace consolidation" (1984, p. 566). He suggested that this latter effect is dependent "upon delta-9THC accumulation in the hippocampus " (p. 563). A relationship between marijuana use, human memory, and dissociation was posited over two decades ago (Stillman, Weingartner, Wyatt, Gillin, & Eich,1974). Stillman et al. found that participants recalled material better when they were in the same marijuana drug state as when they learned the material than if they learned the material in a marijuana-intoxicated state and then tried to recall it in a sober state. They observed that state-dependent recall phenomenawith marijuana in toxification has been demonstrated as well with other drugs, including alcohol, stimulants, and barbiturates. However, these investigators found that the state-dependency effects of marijuana were test-specific, with the picture arrangement test showing especially clear state-dependent effects" (Stillman et al., 1974, p. 84). This test relies on participants having to remember the order or sequence of the pictures and is consistent with the results of Hill, Schwin, Powell, and Goodwin (1973), who also found state-specific effects for recall of ordered objects, but not for word associations or word recall. Thus, marijuana intoxification appears to affect a particular type of memory processing, that is, the temporal ordering of information. Further evidence concerning disruption of temporal memorywas noted by Melges, Tinklenberg, Hollister, and Gillespie (1970). They measured temporal disintegration (defined as a confusion of past, present, and future while a person attempts to pursue goals) both subjectively and objectively. It was subjectively measured by a self-report scale and was objectively measured by a (cognitive) mental arithmetic task. In addition, they measured depersonalization by a 12-item self-report inventory. Melges et al. found that increasing THC concentrations induced significantly greater subjective and cognitive temporal disintegration. Additionally, temporal disintegration and depersonalization were highly correlated (r = .87), suggesting that "as each subject became more temporally disorganized, he simultaneously became more depersonalized" (p. 207). The temporal disintegration was due to "mistakes in serially coordinating and keeping track of information in immediate memory" (p. 209). Miller and Branconnier (1983) suggested that cannabis acts selectively on the limbic system by "modulating the activity of cholinergic neurons in the septal-hippocampal pathway" (p. 441), leading to inconsistent retrieval of information from memoryand memory intrusions. According to Miller and Branconnier, cannabis probably effects two cholinergic limbic circuits: the temporoammonic circuit, which consists of interconnections between the hippocampus, mammillary bodies, anterior and dorsal medial nuclei of the thalamus, limbic, temporal, and entorhinal cortices (Meissner, 1968); and the inhibitory septal-hippocampal circuits to the reticular activating system.(Miller & Branconnier, 1983, p. 453) The first circuit would involve memory decrements involving ineffective retrieval of information from long-term memory, while the second circuit would lead to failure to habituate to novel or irrelevant stimuli. Thus, it seems reasonable to suggest that the same or similar cortical systems are involved in marijuana-induced temporal disintegration and psychological dissociation the limbic system. THE LIMBIC SYSTEM AND HYPNOTIZABILITY Hypnotizability also seems to involve the limbic system in an important way. Hypnotizability is a trait that relates to issues of increased absorption and attention (Hilgard, 1977; Kumar & Pekala, 1988, 1989). Crawford (1994) concluded from her review of the literature that high hypnotizables, relative to lows: a) "demonstrate greater cognitive flexibility, the ability to shift cognitive strategies, and states of awareness, than do lows " (p. 223), and h) have a greater ability " to sustain focused attention on relevant activities and disattend to non-important stimuli in the environment " (p. 223). She further posited that the anterior fronto-limbic system is crucial to this ability. She cited EEG, evoked potential, cerebral blood flow, electrodermal, and neuropsychological studies in support of her conclusions. De Benedittis and Sironi (1986, 1988) have examined the electrical activity of the hippocampus and amygdala of epileptic patients during hypnosis. They suggested that the hypnotic trance state "is associated with the hippocampal activity, concomitantwith a partial amygdaloid complex functional inhibition " (1988, p. 104), and that two relatively discrete aspects of the limbic system, the hippocampus and the amygdala, are probably "the possible neurodynamic core underlying at least some aspects of trance experience" (1988, p. 101). MARIJUANA, DISSOCIATION, HYPNOTIZABILITY, AND THE LIMBIC SYSTEM The aforementioned review suggests that the hippocampal system and related limbic structures are involved in the changes in cognitive processes associated with dissociation, cannabis intoxification, and hypnotizability. Since