Chronic cognitive effects, cannabis

The effects of cannabis on cognition is a complicated issue. Numerous studies have been conducted to measure the mental effects of cannabis, but many of these are fraught with methodological problems. Several variables must be controlled in this type of research, including the dosage and potency of cannabis used, route of administration (e.g., smoking, oral, etc.), chronicity of dose, and the subject population (nonusers, occasional users, chronic users) employed (table 10.7). Population makeup has a large effect on outcome because there have been differences demonstrated between naive and experienced cannabis users (Murray 1986). 

The cognitive effects of cannabis are mild, and have many variables (dosage, chronicity of use, cognitive task employed, etc.). Of prime importance in such studies is the usage (or misusage) of the term impair-... 

Concerns have been raised about the possible adverse effects of acute as well as chronic medicinal and recreational use of cannabis on cognition and the body (104). The author, while acknowledging the therapeutic role of cannabinoids in the management of pain and other conditions, expressed concern that in recent years the prevalence of recreational cannabis use (especially in the young) and the potency of the available products have markedly increased in the UK. 

A study of experienced cannabis smokers tested them on cognitive measures using two doses (1.75% or 3.55%) and placebo (Wilson et al. 1994). The functions most sensitive to the effects of THC were mental processing speed (digit-symbol substitution) and reaction time. When compared with cannabis nonusers, chronic users of cannabis—with a mean duration of use of 6.76 years and an average daily intake of 150 mg of THC—were found to have slower reactions on perceptuo-motor tasks, but no differences on intelligence or memory tests (Varma et al. 1988). 

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