Marihuana "High": A Model of Senile Dementia?

MARIHUANA "HIGH": A MODEL OF SENILE DEMENTIA? ADAM SULKOWSKI* The evidence for marihuana-induced brain atrophy [ 1] and "amotivational syndrome" [1,2] has not been convincing so far [3-8]. There are, however, some striking similarities between certain features of acute marihuana intoxication and the clinical syndromes of presenile and senile dementia (Alzheimer's disease). These similarities become puzzling and thought provoking when one compares the experimental psychological , neurophysiological, neuropathological, and pharmacological studies of these two, apparently so different, phenomena. Psychological studies of acute intoxication with marihuana of mild to moderate potency have shown no effects on sensory acuity and simple reaction time tests [9-11]. Psychogeriatric literature provides no evidence for motor and/or sensory deficits in early stages of Alzheimer's disease [12, 13]. Careful studies of attention, psychomotor speed, memory and learning in our laboratory [11, 14] have not shown marihuanainduced impairment except for the subjects' ability to use effectively already memorized task-relevant information. We called this deficit a failure in information processing. The same finding has been repeatedly described by many authors in the aged and demented populations [15, 16]. Another intriguing similarity is in self-evaluation regarding one's performance. Under the influence of marihuana—and in contrast to alcohol effects—people tend to perceive their performance as much worse than it is in reality (i.e., they overestimate impairment) and as the result they exercise considerable caution and restraint (Sulkowski, unpublished data). As a matter of fact, in real life, marihuana users are said to occasionally endanger safety by driving too slowly. One needs only to observe daily traffic to see how exasperatingly "cautious" elderly people can be. This age-related psychological characteristic has been dealt with extensively by psychologists of old age [17-19].»Bedford VA Medical Center GRECC, 200 Springs Road, Bedford, Massachusetts 01730 and Boston University School of Medicine.© 1980 by The University of Chicago. 0031-5982/80/2302-0139$01.00 Perspectives in Biology andMedicine · Winter 1980 \ 209 A unique and reliable effect ofmarihuana is alteration in time perception which has been seen especially clearly in "time production" paradigm (e.g., a subject is asked to signal the limits of a 10-second interval of time) [14, 20, 21]. It has been speculated that the drug alters our internal psychological clock. Identical defects in this hypothetical clock have been described in the elderly and have been considered responsible for decrements on many behavioral tests [22, 23]. Some experts contend that the left (dominant) hemisphere functions are more affected by marihuana than the right (nondominant) hemisphere functions [24, 25]. This reportedly results in disinhibition of the right hemisphere and leads to an altered state of consciousness. Recently published neurological theories postulate that this interhemispheric imbalance is responsible for clinical symptoms of dementia [26]. Rigorous tests of these theories are difficult to design [27] and supportive experimental data are very scant. On the psychosocial (interpersonal) level marihuana produces a quiet detached withdrawal from social environment which might be an analogue of so-called gradual social disengagement typical of very old and demented individuals [28]. It is possible that the failure to actively process information when "high" reinforces marihuana use through the mechanism of negative reinforcement by protecting the user from stressful cognitive overload with multiple and contradictory messages typical of modern society. Neurophysiological data from EEG studies of marihuana's acute effects show nonspecific and generalized slowing of alpha rhythm and slight to moderate increase in amplitude [29, 30]. These also happen to be the most common findings in very old subjects and patients suffering from Alzheimer's disease [31, 32]. Psychophysiological theorists ofaging have provided some experimental data to support their theory of autonomic nervous system overarousal in the aged and demented [33, 34]. This hyperarousal has been held responsible for interoceptive sensory overload which in turn interfered with CNS adaptive functions. Powerful sympathetic activation is a characteristic and dose-related effect of marihuana. Difficulties with theoretical interpretation notwithstanding, the decrease in cerebral blood flow in Alzheimer's disease has been well documented. Again, there are some preliminary data (L. Miller, personal communication) suggestive of diminished blood supply to the brain in intoxicated marihuana smokers. Pharmacologic studies seem to indicate...