RESULTS Although causality is unclear , heavy and dependent cannabis use is consistently associated with a high prevalence of comorbid psychiatric disorders and learning and memory impairments that seem to recover after a period of abstinence .
Evidence regarding other cognitive domains and neurological consequences including cerebrovascular events is limited and inconsistent .
Abstinence after treatment is only achieved in a minority of cases ; treatment targeted at reduction in use appears have some success .
Potential moderators of the impact of CUD on the brain include age of onset , heaviness of use , CUD severity , the ratio of ∆9-tetrahydrocannabinol to cannabidiol , and severity of comorbid disorders .
Current evidence of long-term effects of daily cannabis use and cannabis use disorder on brain-related outcomes is suggestive rather than conclusive but use is associated with psychiatric morbidity and with cognitive impairments that recover after a period of abstinence
AIMS To summarize and evaluate our knowledge of the relationship between heavy cannabis use , Cannabis Use Disorder ( CUD ) , and the brain .
Verbal learning and memory in adolescent cannabis users, alcohol users and non-users
Rationale Long-term heavy cannabis use can result in memory impairment .  Adolescent users may be especially vulnerable to the adverse neurocognitive effects of cannabis . Objectives and methods In a cross-sectional and prospect i ve neuropsychological study of 181 adolescents aged 16–20 ( mean 18.3 years ) , we compared performance indices from one of the most widely used measures of learning and memory — the Rey Auditory Verbal Learning Test — between cannabis users ( n = 52 ; mean 2.4 years of use , 14 days/month , median abstinence 20.3 h ) , alcohol users ( n = 67 ) and non-user controls ( n = 62 ) matched for age , education and premorbid intellectual ability ( assessed prospect ively ) , and alcohol consumption for cannabis and alcohol users . Results Cannabis users performed significantly worse than alcohol users and non-users on all performance indices . They recalled significantly fewer words overall ( p < 0.001 ) , demonstrating impaired learning ( p < 0.001 ) , retention ( p < 0.001 ) and retrieval ( p < 0.05 ) ( Cohen ’s d 0.43–0.84 ) . The degree of impairment was associated with the duration , quantity , frequency and age of onset of cannabis use , but was unrelated to alcohol exposure or other drug use . No gender effects were detected and the findings remained after controlling for premorbid intellectual ability . An earlier age of onset of regular cannabis use was associated with worse memory performance after controlling for extent of exposure to cannabis . Conclusions Despite relatively brief exposure , adolescent cannabis users relative to their age-matched counterparts demonstrated similar memory deficits to those reported in adult long-term heavy users . The results indicate that cannabis adversely affects the developing brain and reinforce concerns regarding the impact of early exposure
RESULTS Although causality is unclear , heavy and dependent cannabis use is consistently associated with a high prevalence of comorbid psychiatric disorders and learning and memory impairments that seem to recover after a period of abstinence .
Evidence regarding other cognitive domains and neurological consequences including cerebrovascular events is limited and inconsistent .
Abstinence after treatment is only achieved in a minority of cases ; treatment targeted at reduction in use appears have some success .
Potential moderators of the impact of CUD on the brain include age of onset , heaviness of use , CUD severity , the ratio of ∆9-tetrahydrocannabinol to cannabidiol , and severity of comorbid disorders .
Current evidence of long-term effects of daily cannabis use and cannabis use disorder on brain-related outcomes is suggestive rather than conclusive but use is associated with psychiatric morbidity and with cognitive impairments that recover after a period of abstinence
AIMS To summarize and evaluate our knowledge of the relationship between heavy cannabis use , Cannabis Use Disorder ( CUD ) , and the brain .