Neuropsychological Performance in Long-term Cannabis Users

Abstract

Some cognitive deficits appear detectable at least 7 days after heavy cannabis use but appear reversible and related to recent cannabis exposure rather than irreversible and related to cumulative lifetime use.

Abstinent adolescent marijuana users show altered fMRI response during spatial working memory

“…This could relate to residual drug effects or withdrawal symptoms during early abstinence, less need for neural compensation, or a change in neurocognitive strategy as the brain adapts to different stages of sobriety. We did not observe a correlation between brain response and recency of marijuana use in this sample, but most neuropsychological recovery appears to occur during the first week of abstinence (Pope et al, 2001). Thus, there may be little change in neurocognitive functioning after 28 days of abstinence, or such an effect may be too subtle to detect with a relatively small sample.…”

“…However, it is unclear whether these neurocognitive findings only represent effects of recent use. Pope et al (2001) demonstrated deficits on verbal learning up to 7 days after use among current heavy marijuana users compared with former users and non-using controls. However, after 28 days of abstinence, current users performed similarly to former users and controls on all tests, suggesting that neurocognitive decrements may resolve within a month of abstinence (Pope et al, 2001).…”

“…Pope et al (2001) demonstrated deficits on verbal learning up to 7 days after use among current heavy marijuana users compared with former users and non-using controls. However, after 28 days of abstinence, current users performed similarly to former users and controls on all tests, suggesting that neurocognitive decrements may resolve within a month of abstinence (Pope et al, 2001). Importantly, fMRI evidence indicates that both abstinent users and active users show brain response abnormalities relative to controls during visual attention (Chang et al, 2006), suggesting lasting changes in patterns of neural activity.…”

“…After controlling for baseline performance and demographics, they found that current heavy marijuana users showed deficits in immediate and delayed memory, processing speed, and overall IQ. Further, a longitudinal study of 10 cannabis-dependent adolescents demonstrated incomplete recovery of learning and memory impairments after 6 weeks of monitored abstinence (Schwartz et al, 1989), indicating that adolescents may be more susceptible to long-term changes than adults (Pope et al, 2001). Together, these studies point to dysfunctional working memory and attention abilities among adolescents who are heavy marijuana users that may persist after several weeks of abstinence.…”

Cannabis Use Disrupts Eyeblink Conditioning: Evidence for Cannabinoid Modulation of Cerebellar-Dependent Learning

“…This last issue regarding whether EBC performance is recoverable will be important to elucidate from a public health perspective. Current neuropsychological data suggest a recovery of cannabis-induced cognitive impairments after 1 month of abstinence (Pope et al, 2001;Harrison et al, 2002). However, these neuropsychological tasks are typically sensitive to distributed cortical networks not specific to cerebellar processes, as is the EBC procedure.…”