Differential Association Between Chronic Cannabis Use and Brain Function Deficits

Abstract

To summarize, 12 objective tests that generated 16 test variables were administered to 850 male regular cannabis users and 839 nonusers. The tests were designed to assess various modalities, including speed of psychomotor performance, distance estimation, time estimation, immediate memory, and visuomotor coordination. Most of the test variables differentiated significantly between consumers and controls. At the same time, a significant second-order interaction emerged in most cases. This interaction meant that, under certain conditions that relate to the two dimensions "literacy-illiteracy" and/or "urbanism-ruralism," the superiority of controls over cannabis users became impressive, whereas under other conditions it almost disappeared. To account for this complex pattern of results, a working hypothesis was presented to the effect that "other conditions being equal, the lower the nondrug level of proficiency on tests of cognitive and psychomotor performance the smaller the size of function deficit associated with drug usage." For an empirical examination of the hypothesis, six predictions were formulated. Three predictions defined specific relationships between level of performance, on one hand, and each of three organismic variables, on the other: literacy, urbanism, and age. The remaining predictions delineated relationships to be expected between size of function deficit and the three organismic variables. All our predictions were confirmed, showing less function impairment to be contingent with cannabis usage among the illiterates, rurals, and older subjects. Level of cortical arousal was suggested as the central process associated with the three organismic variables. Because the version of our working hypothesis was formulated with reference to chronic material, the possibility of a transposition of the paradign to research on the acute effects of the drug was discussed. The suggestion was made that our working hypothesis, in either version, is capable of establishing genuine integration between reports that present conflicting results on possible function deficits contingent with cannabis consumption.

The effects of cannabis on memory function in users with and without a psychotic disorder: findings from a combined meta-analysis

“…5). More speculatively, this may be related to the changing potency of cannabis that is used recreationally (Bowman & Pihl, 1973; Soueif, 1976). In contrast to old-fashioned herbal cannabis and resin consumed in the 1970s and 1980s, for example comprising about 3–4% THC (Poulsen & Sutherland, 2000), THC content in currently available herbal cannabis has increased to about 8%, and ‘skunk’ or sinsemilla is increasingly dominating the market in the UK and other European countries, a more potent variant containing about 16% THC (Hardwick & King, 2008).…”

Residual effects of cannabis use on neurocognitive performance after prolonged abstinence: A meta-analysis.

“…Several studies were unable to find cognitive effects among moderate to heavy cannabis users (Bowman & Pihl, 1973;Carlin & Trupin, 1977;Grant, Rochford, Fleming, & Stunkard, 1973). Other studies, however, found residual effects on verbal memory, attention, speed and accuracy, and perceptual-motor tasks among cannabis users when compared to controls (Entin & Goldzung, 1973;Fletcher et al, 1996;Soueif, 1976;Varma, Malhotra, Dang, Das, & Nehra, 1988). In a review of empirical literature on residual effects of cannabis, major methodological problems afflicting most of the existing research were identified and may explain these seemingly inconsistent findings (Pope, Gruber, & Yurgelun-Todd, 1995).…”

Possible amotivational effects following marijuana smoking under laboratory conditions.

“…The amotivational syndrome is a set of characteristics that frequently have been associated with chronic marijuana use (McGlothlin & West, 1968; Smith, 1968). Specific characteristics of the amotivational syndrome that have been noted are general apathy (Bindelglas, 1973; Kolansky & Moore, 1972, 1975; Smith, 1970), loss of productivity (McGlothlin & West, 1968; Nahas, 1976; Soueif, 1976), difficulty in carrying out long-range plans (Page, 1983), lethargy (Brill et al, 1970; Kolansky & Moore, 1975), depression (Bindelglas, 1973; Kolansky & Moore, 1975), inability to concentrate (Bindelglas, 1973, Soueif, 1976), and inability to sustain attention (Kolansky & Moore, 1972; Smith, 1970).…”