Acute and chronic effects of cannabinoids on effort-related decision-making and reward learning: an evaluation of the cannabis ‘amotivational’ hypotheses

Abstract

RationaleAnecdotally, both acute and chronic cannabis use have been associated with apathy, amotivation, and other reward processing deficits. To date, empirical support for these effects is limited, and no previous studies have assessed both acute effects of Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), as well as associations with cannabis dependence.ObjectivesThe objectives of this study were (1) to examine acute effects of cannabis with CBD (Cann + CBD) and without CBD (Cann-CBD) on effort-related decision-making and (2) to examine associations between cannabis dependence, effort-related decision-making and reward learning.MethodsIn study 1, 17 participants each received three acute vaporized treatments, namely Cann-CBD (8 mg THC), Cann + CBD (8 mg THC + 10 mg CBD) and matched placebo, followed by a 50 % dose top-up 1.5 h later, and completed the Effort Expenditure for Rewards Task (EEfRT). In study 2, 20 cannabis-dependent participants were compared with 20 non-dependent, drug-using control participants on the EEfRT and the Probabilistic Reward Task (PRT) in a non-intoxicated state.ResultsCann-CBD reduced the likelihood of high-effort choices relative to placebo (p = 0.042) and increased sensitivity to expected value compared to both placebo (p = 0.014) and Cann + CBD (p = 0.006). The cannabis-dependent and control groups did not differ on the EEfRT. However, the cannabis-dependent group exhibited a weaker response bias than the control group on the PRT (p = 0.007).ConclusionsCannabis acutely induced a transient amotivational state and CBD influenced the effects of THC on expected value. In contrast, cannabis dependence was associated with preserved motivation alongside impaired reward learning, although confounding factors, including depression, cannot be disregarded. This is the first well powered, fully controlled study to objectively demonstrate the acute amotivational effects of THC.Electronic supplementary materialThe online version of this article (doi:10.1007/s00213-016-4383-x) contains supplementary material, which is available to authorized users.

Can we make cannabis safer?

“…A recent study found that CBD given orally up to 800mg did not influence the pleasurable, reinforcing or intoxicating effects of a smoked cannabis cigarette (~4.4mg THC) 23 . Two studies of inhaled cannabis vapour, with combinations including 8mg THC, 8mg THC + 10mg CBD and 8mg THC + 16mg CBD, found no differences in ratings of 'stoned' 24,25 . Lastly, a study where participants smoked their own cannabis found no difference in 'stoned' ratings when comparing low to high CBD:THC ratio strains of cannabis 26 .…”

Neuropsychiatric Effects of Marijuana

“…In simple terms, a joint made out of skunkweed, nether weed and other potent subspecies of Cannabis sativa, may contain around 150 mg of THC, or 300 mg if laced with hashish oil. Thus, the modern cannabis smoker may be exposed to doses of THC many times greater than its counterpart of the 1960s and 1970s; 2,6 yet another argument as to why its use among young people and their developing brains is worrisome (Figure 1). …”

“…Although many studies argue about tolerance, dependence and withdrawal in Cannabis use, 6 these effects are substantial. Moreover, tolerance, dependence, withdrawal effects can develop over time from chronic cannabis use.…”

“…2,15 Further, in spite of skepticism, long term use of Cannabis has also been linked to a motivational syndrome. 6 A motivational syndrome presents like a depression and is symptomatic of apathy, dullness, lethargy, and impairment of judgment. …”

Another Nasty Effect of Opioids: Attenuating the Benefits of Motivational Interviewing in Fibromyalgia?

“…It is possible that even a low dose of opioids suffices to affect motivation in susceptible persons and we know that adverse mood changes and hormonal effects are associated with more prolonged administration of opioids 17,18 . Finally, molecules closely aligned with opioids are the cannabinoids, which are known to induce an "amotivational" disorder 19 . Although it would be incorrect to extrapolate to opioids the cannabinoid effects on motivation, the similarities in adverse and psychoactive effects of these 2 drug categories suggests that amotivation may also be a plausible effect of opioids.…”