Abstract
BackgroundThe present study assessed psychomotor function in chronic, daily cannabis smokers during 3 weeks continuously monitored abstinence on a secure research unit. We hypothesized that psychomotor performance would improve during abstinence of chronic, daily cannabis smokers.Methodology/Principal FindingsPerformance on the critical tracking (CTT) and divided attention (DAT) tasks was assessed in 19 male chronic, daily cannabis smokers at baseline and after 8, 14–16 and 21–23 days of continuously monitored abstinence. Psychomotor performance was compared to a control group of non-intoxicated occasional drug users. Critical frequency (λc) of the CTT and tracking error and control losses of the DAT were the primary outcome measures. Results showed that chronic cannabis smokers’ performance on the CTT (p<0.001) and the DAT (p<0.001) was impaired during baseline relative to the comparison group. Psychomotor performance in the chronic cannabis smokers improved over 3 weeks of abstinence, but did not recover to equivalent control group performance.Conclusions/SignificanceSustained cannabis abstinence moderately improved critical tracking and divided attention performance in chronic, daily cannabis smokers, but impairment was still observable compared to controls after 3 weeks of abstinence. Between group differences, however, need to be interpreted with caution as chronic smokers and controls were not matched for education, social economic status, life style and race.
Highlights
Cannabis is the most commonly used illicit substance worldwide [1]
Pearson R analyses revealed that age was not significantly correlated with critical tracking and divided attention performance parameters of chronic daily smokers and controls (r = 20.06, p = 0.679; r = 20.049, p = 0.738; r = 0.276, p = 0.055 for the CTT, control losses and tracking error of the DAT respectively)
Results showed that psychomotor performance of chronic, daily cannabis smokers improved throughout 3 weeks of abstinence, but remained significantly poorer than performance of a control group of occasional drug users
Summary
Cannabis is the most commonly used illicit substance worldwide [1]. In 2009, approximately 1.7% of Americans 12 years or older were cannabis dependent [2], and greater than 1% of Europeans smoked cannabis daily or almost daily [3].Long-term cannabis use is associated with neuropsychological deficits such as memory impairment (e.g. [4,5,6]) and changes in brain morphology [7]. Long-term cannabis use is associated with neuropsychological deficits such as memory impairment As performance in long-term cannabis smokers returned to normal over 3 weeks of abstinence [8]. CB1 receptor density was down-regulated in chronic, daily cannabis smokers, returning to normal levels after 4 weeks abstinence [11]. Together, these data indicate that cannabisrelated memory alterations and CB1 receptor down-regulation in chronic cannabis smokers are reversible and related to recent use, rather than irreversible and related to cumulative lifetime intake.It is not clear if other neuropsychological dysfunctions observed in long-term cannabis smokers such as psychomotor impairment, are transient. We hypothesized that psychomotor performance would improve during abstinence of chronic, daily cannabis smokers
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