Psychomotor Function in Chronic Daily Cannabis Smokers during Sustained Abstinence

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.

Phase I and II Cannabinoid Disposition in Blood and Plasma of Occasional and Frequent Smokers Following Controlled Smoked Cannabis

“…In frequent smokers, 16.7% of participants were positive for Ͼ30 h at 5 g/L. There is evidence supporting continued psychomotor impairment after 3 weeks of abstinence in chronic frequent smokers (19 ), suggesting that driving ability is impaired at the time of these low blood THC concentrations. Hence, long windows of detection may be necessary to document residual impairment.…”

Acute and Chronic Effects of Cannabinoids on Human Cognition—A Systematic Review

“…Numerous studies report impairment in adolescent and adult cannabis users with a wide range of exposure as well as former users abstinent for several weeks on measures of sustained and divided attention, processing speed, rapid visual information processing, visual search, tracking, trail making, and paced serial addition (46,54,55,57,61,(91)(92)(93)(94). Users abstinent for 23 days remained impaired relative to control subjects despite improvements in sustained and divided attention with increasing abstinence (91) with poor attentional performance associated with younger age of onset in this study (91) and another study of adolescents abstinent for 30 days (95). However, no difference between abstinent former users and control subjects on broader measures of attention was also reported (57,63,64,79,95).…”

“…Findings regarding the chronic effects of cannabis on psychomotor function are mixed, being reported as impaired (51,54,80,108), improved (48), and unaffected (46,78). Psychomotor function was impaired in users abstinent for 23-35 days (57,65,67,91), with a trend also after 12 months of abstinence (finger tapping) (64). The weight of evidence suggests that psychomotor function is affected by acute intoxication and that this likely persists for some time after chronic cannabis exposure.…”

Legalizing marijuana

“…1,2 Chronic users exhibit cognitive deficits, 1,3 and up to 15% of users will become dependent. 2,4 During periods of abstinence, milder cognitive and psychomotor impairments can persist for weeks in heavy users (average 11 joints per day for 10 years), 5 similar to the extended withdrawal effects seen following the chronic use of other substances. 6,7 Neurobiological differences in brain structure, 8 connectivity, 9 and function 10 have been tentatively identified, though some morphological differences, at least, might reflect pre-existing traits.…”