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 .
High-Potency Marijuana Impairs Executive Function and Inhibitory Motor Control
Human performance studies have usually relied on low-potency marijuana ( 4 % THC ) for determining THC-induced impairment . The present study was design ed to assess the effects of high-potency marijuana ( 13 % THC ) on human performance . In all , 20 recreational users of marijuana participated in a double-blind ,  placebo  controlled , three way cross-over study . The treatments consisted of single doses of 0 , 250 , and 500 μg/kg THC .  Performance tests were conducted at regular intervals between 15 min and 6 h postsmoking and included measures of motor control ( Critical tracking task ) , executive function ( Tower of London ) motor impulsivity ( Stop signal task ) , and risk taking ( Iowa gambling task ) . THC significantly impaired performance in the Critical tracking task and decreased the number of correct decisions in the Tower of London task . In addition , THC significantly increased stop reaction time and the proportions of commission and omission errors in the Stop signal task . THC-induced impairments lasted up to 6 h postsmoking as indicated by the absence of a THC × Time after smoking interaction . Effect sizes for performance impairments produced by THC 250 μg/kg were relatively low but generally increased by a factor of two in case of THC 500 μg/kg . These data suggest that high potency marijuana consistently impairs executive function and motor control . Use of higher doses of THC in controlled studies may offer a reliable indication of THC induced impairment as compared to lower doses of THC that have traditionally been used in performance studies
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 .