Cannabis and Cognitive Functions: a re‐evaluation study

Abstract

Out of 25 each of long-term, heavy bhang (marihuana) ingestors, 25 charas (hashish) smokers and 25matched non-user controls earlier studied and reported by us, 11 bhang users, 19 charas smokers and 15 controls could be re-studied after a lapse of 9-10 years. All the users had continued the use during the intervening years. Tests of intelligence, memory and perceptuo-motor tasks earlier administered to the subjects were repeated. This showed a significant additional deterioration in case of the users on a number of psychological measures, i.e. on digit span, speed and accuracy tests, reaction time and Bender visuo-motor gestalt test. The deterioration in the cannabis users was significantly greater than in the case of the non-users controls. The study thus further corroborates our earlier findings of impairment of cognitive functions associated with long-term, heavy cannabis use.

Role of cannabis and endocannabinoids in the genesis of schizophrenia

“…Schneier and Siris (1987) propose that there is a clear association between the emergence of psychotic symptoms and personality alterations in cannabis abusers. Mendhiratta et al (1988) reported that neuroticism as evaluated through the Minnesota Multiphasic Personality Inventory test is more intense in subjects with toxic psychosis, and Negrete (1983) reported similar results.…”

Hormonal status and age differentially affect tolerance to the disruptive effects of delta-9-tetrahydrocannabinol (Δ9-THC) on learning in female rats

“…Foremost among the findings from longitudinal studies such as the Dunedin study are that executive functioning ( Meier et al, 2012 ) and processing speed or reaction time ( Mendhiratta et al, 1988 ; Wilson et al, 1994 ; Hunault et al, 2009 ) tend to be the most susceptible to the long-term marijuana use and that disruptions of these neurocognitive processes can eventually lead to motivational and academic difficulties (for reviews, see Lynskey and Hall, 2000 ; Gruber and Pope, 2002 ; Volkow et al, 2014 ). These findings have also been bolstered by the human studies examining the acute and chronic effects of Δ 9 -THC, which have documented Δ 9 -THC-induced disruptions in a number of domains of neuropsychological functioning.…”

Neuropsychological consequences of regular marijuana use: a twin study

“…Pope et al (2002) found similar memory impairments up to 7 days after marijuana use ceased, but were unable to find a significant difference between users and controls after 28 days of abstinence. Other studies provide mixed evidence regarding residual neuropsychological deficits resulting from marijuana use (Mendhiratta et al 1988;Schwartz et al 1989 ;Solowij et al 1991 ;Lyketsos et al 1999 ;Varma et al 2000). Where differences between users and non-users have been found, they are often on only one or two tests out of a large number administered ; moreover, the differences are often modest, and users' scores are usually within the range of normal cognitive variability (Block & Ghoneim, 1993).…”