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 .
Developmental sensitivity to cannabis use patterns and risk for major depressive disorder in mid-life: findings from 40 years of follow-up.
BACKGROUND Evidence regarding the association between cannabis use and depression  remain conflicting , especially as studies have not typically adopted a longitudinal design with a follow-up period that was long enough to adequately cover the risk period for onset of depression . METHOD Males from the Cambridge Study in Delinquent Development ( CSDD ) ( N = 285 ) were assessed seven times from age 8 to 48 years to prospect ively investigate the association between  cannabis use and risk of  major depressive disorder ( MDD ) .  A combination of multiple analyses ( logistic regression , Cox regression , fixed-effects analysis ) was employed to explore the strength and direction of effect within different developmental stages . RESULTS Multiple regression analyses revealed that early-onset cannabis use ( before age 18 ) but not late-onset cannabis use ( after age 27 ) was associated with a higher risk and shorter time until a subsequent MDD diagnosis . This effect was present in high-frequency [ ( odds ratio ( OR ) 8.83 , 95 % confidence interval ( CI ) 1.29 - 70.79 ] ; [ hazard ratio ( HR ) 8.69 , 95 % CI 2.07 - 36.52 ) ] and low-frequency early-onset users ( OR 2.41 , 95 % CI 1.22 - 4.76 ; HR 2.09 , 95 % CI 1.16 - 3.74 ) . Effect of increased frequency of cannabis use on increased risk of subsequent MDD was observed only for use during adolescence ( age 14 - 18 ) but not at later life stages , while controlling for observed and non-unobserved time-invariant factors . Conversely , MDD in adulthood ( age 18 - 32 ) was linked to a reduction in subsequent cannabis use ( age 32 - 48 ) . CONCLUSIONS The present findings provide evidence implicating frequent cannabis use during adolescence as a risk factor for later life depression . Future studies should further examine causality of effects in larger sample
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 .