Is Cannabis Use Associated with Various Indices of Motivation among Adolescents?

Anhedonia, Apathy, Pleasure, and Effort-Based Decision-Making in Adult and Adolescent Cannabis Users and Controls

BACKGROUND

Cannabis use may be linked with anhedonia and apathy. However, previous studies have shown mixed results, and few have examined the association between cannabis use and specific reward sub-processes. Adolescents may be more vulnerable than adults to harmful effects of cannabis. This study investigated (1) the association between non-acute cannabis use and apathy, anhedonia, pleasure, and effort-based decision-making for reward; and (2) whether these relationships were moderated by age group.

METHODS

We used data from the "CannTeen" study. Participants were 274 adult (26-29 years) and adolescent (16-17 years) cannabis users (1-7 d/wk use in the past 3 months) and gender- and age-matched controls. Anhedonia was measured with the Snaith-Hamilton Pleasure Scale (n = 274), and apathy was measured with the Apathy Evaluation Scale (n = 215). Effort-based decision-making for reward was measured with the Physical Effort task (n = 139), and subjective wanting and liking of rewards was measured with the novel Real Reward Pleasure task (n = 137).

RESULTS

Controls had higher levels of anhedonia than cannabis users (F1,258 = 5.35, P = .02, η p2 = .02). There were no other significant effects of user-group and no significant user-group*age-group interactions. Null findings were supported by post hoc Bayesian analyses.

CONCLUSION

Our results suggest that cannabis use at a frequency of 3 to 4 d/wk is not associated with apathy, effort-based decision-making for reward, reward wanting, or reward liking in adults or adolescents. Cannabis users had lower anhedonia than controls, albeit at a small effect size. These findings are not consistent with the hypothesis that non-acute cannabis use is associated with amotivation.

Effort-based decision making and self-reported apathy in frequent cannabis users and healthy controls: A replication and extension

INTRODUCTION

Amotivational syndrome is a term used to refer to lack of motivation and passive personality related to chronic cannabis use. Given mixed findings, the current study aimed to replicate and extend previous research on frequent cannabis use, motivated behavior, and self-reported apathy.

METHOD

Cannabis users (on average, ≥3 days/week of cannabis use over the past year), and healthy controls (≤1 day/month of cannabis use over the past year) completed the Apathy Evaluation Scale (AES), and the Effort Expenditure for Rewards Task (EEfRT). Repeated measures analysis of covariance was used to 1) examine the effects of group, reward magnitude, probability, and their interaction on hard task selections on the EEfRT, and 2) examine between-group differences on the AES, controlling for alcohol use and depressive symptoms.

RESULTS

There were significant main effects of reward magnitude, probability, and an interaction between reward magnitude and probability on hard task selection (p's < 0.05). Specifically, as reward magnitude and probability of winning the reward increased, participants were more likely to select hard tasks on the EEfRT. Relative to healthy controls, cannabis users were significantly more likely to select hard tasks on the EEfRT (F(1,56) = 6.49, p = 0.014, η_p² = 0.10). When controlling for alcohol use and depressive symptoms, no significant group differences in self-reported apathy were present (p = 0.46).

CONCLUSIONS

Cannabis users exhibit a greater likelihood of exerting more effort for reward, suggesting enhanced motivation relative to healthy controls. Thus, the current results do not support amotivational syndrome in adult frequent cannabis users. Despite some harms of long-term cannabis use, amotivation may not be among them.

Apathy and Anhedonia in Adult and Adolescent Cannabis Users and Controls Before and During the COVID-19 Pandemic Lockdown

BACKGROUND

COVID-19 lockdown measures have caused severe disruptions to work and education and prevented people from engaging in many rewarding activities. Cannabis users may be especially vulnerable, having been previously shown to have higher levels of apathy and anhedonia than non-users.

METHODS

In this survey study, we measured apathy and anhedonia, before and after lockdown measures were implemented, in n = 256 adult and n = 200 adolescent cannabis users and n = 170 adult and n = 172 adolescent controls. Scores on the Apathy Evaluation Scale (AES) and Snaith-Hamilton Pleasure Scale (SHAPS) were investigated with mixed-measures ANCOVA, with factors user group, age group, and time, controlling for depression, anxiety, and other drug use.

RESULTS

Adolescent cannabis users had significantly higher SHAPS scores before lockdown, indicative of greater anhedonia, compared with adolescent controls (P = .03, η p2 = .013). Contrastingly, adult users had significantly lower scores on both the SHAPS (P < .001, η p2 = .030) and AES (P < .001, η p2 = .048) after lockdown compared with adult controls. Scores on both scales increased during lockdown across groups, and this increase was significantly smaller for cannabis users (AES: P = .001, η p2 = .014; SHAPS: P = .01, η p2 = .008). Exploratory analyses revealed that dependent cannabis users had significantly higher scores overall (AES: P < .001, η p2 = .037; SHAPS: P < .001, η p2 = .029) and a larger increase in scores (AES: P = .04, η p2 =.010; SHAPS: P = .04, η p2 = .010), compared with non-dependent users.

CONCLUSIONS

Our results suggest that adolescents and adults have differential associations between cannabis use as well as apathy and anhedonia. Within users, dependence may be associated with higher levels of apathy and anhedonia regardless of age and a greater increase in levels during the COVID-19 lockdown.

The acute and non-acute effects of cannabis on reward processing: A systematic review

Cannabis use has historically been thought to cause amotivation, but the relationship between cannabis and apathy, anhedonia, and reward processing remains poorly characterised. In this systematic review, we evaluated whether cannabis exposure acutely and/or non-acutely was associated with altered reward processing using questionnaire, behavioural, or functional neuroimaging measures. Questionnaire studies demonstrated greater anhedonia in adolescent cannabis users, and some indication of greater apathy in young adult cannabis users. Behavioural studies yielded some evidence of reduced reward learning in adolescent cannabis users, though there were too few studies in this category for reliable conclusions. Finally, longitudinal and acute functional neuroimaging studies showed an association between cannabis and blunted neural responses to reward, which did not emerge consistently in cross-sectional studies. The current results suggest that cannabis use is associated with specific impairments in reward and motivation. Future large-scale, longitudinal studies which use multiple behavioural and neuroimaging measures of reward processing may further clarify the impact of cannabis use on motivational and reward processes, and neural networks.

Residual Effects of Cannabis Use on Effort-Based Decision-Making

OBJECTIVE

Acute Δ9-tetrahydrocannabinol (THC) administration in humans (Lawn etal., 2016) and rats (Silveira, Adams, Morena, Hill, & Winstanley, 2016) has been associated with decreased effort allocation that may explain amotivation during acute cannabis intoxication. To date, however, whether residual effects of cannabis use on effort-based decision-making are present and observable in humans have not yet been determined. The goal of this study was to test whether prolonged cannabis use has residual effects on effort-based decision-making in 24-hr abstinent cannabis using adults.

METHOD

We evaluated performance on the Effort Expenditure for Reward Task (EEfRT) in 41 adult cannabis users (mean age = 24.63 years, 21 males) and 45 nonusers (mean age = 23.90 years, 19 males). A mixed 2x3x3 ANOVA with age as a covariate was performed to examine the effect of group, probability of winning, and reward amount on EEfRT performance. EEfRT performance was operationalized as % of trials for which the hard (vs. easy) condition was chosen. Pearson's correlations were conducted to test the relationship between EEfRT performance and measures of cannabis use, anhedonia and motivation.

RESULTS

We found that cannabis users selected hard trials significantly more than nonusers regardless of win probability or reward level. Frequency of cannabis use was positively correlated with amount of % hard trials chosen. There were no significant correlations between % hard trials chosen, self-reported anhedonia, or motivation.

CONCLUSIONS

These results suggest that unlike acute effects, residual effects of cannabis following 24 hrs of abstinence are associated with greater effort allocation during effort-based decision-making.

Evidence Lacking for Cannabis Users Slacking: A Longitudinal Analysis of Escalating Cannabis Use and Motivation among Adolescents

OBJECTIVE

Reduced motivation is often noted as a consequence of cannabis use. However, previous work has yielded mixed results and focused largely on adults. To address these limitations, this study examined longitudinal associations between cannabis use and self-reported motivation in a large adolescent sample.

METHOD

Participants were 401 adolescents aged 14-17 at baseline who completed five bi-annual assessments. We assessed motivation at three timepoints using two self-report questionnaires: the Apathy Evaluation Scale and the Motivation and Engagement Scale (disengagement, persistence, planning, self-efficacy, and valuing school subscales). Controlling for relevant covariates, we used latent growth curve modeling to characterize patterns of cannabis use and motivation over time, examining bidirectional influences between these processes.

RESULTS

On average, adolescent cannabis use frequency increased significantly over time. The disengagement and planning facets of motivation also increased significantly over time, whereas other aspects of motivation remained stable. At baseline, greater cannabis use was associated with greater disengagement, lower planning, and lower valuing of school. Greater baseline cannabis use also predicted lesser increases in disengagement over time. After controlling for the effect of sex, age, depression, and use of alcohol and nicotine, only the baseline association between cannabis use and valuing school remained significant.

CONCLUSIONS

Our results do not support a prospective link between cannabis use and reduced motivation among adolescents. Although most observed associations were accounted for by covariates, greater cannabis use was cross-sectionally associated with lower perceived value of school, which may contribute to poorer educational and later life outcomes.

The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review

Background: Cannabis is known to have a broad range of effects on behavior, including experiencing a "high" and tranquility/relaxation. However, there are several adverse behavioral sequalae that can arise from cannabis use, depending on frequency of use, potency (e.g., THC content), age of onset, and cumulative exposure. This systematic review examined evidence for cannabis-related adverse behavioral sequalae in otherwise healthy human subjects. Methods: Following PRISMA guidelines, we conducted a systematic review of cross-sectional and longitudinal studies from 1990 to 2020 that identified cannabis-related adverse behavioral outcomes in subjects without psychiatric and medical co-morbidities from PubMed and PsychInfo searches. Key search terms included "cannabis" OR "tetrahydrocannabinol" OR "cannabidiol" OR "marijuana" AND "anxiety" OR "depression" OR "psychosis" OR "schizophrenia" "OR "IQ" OR "memory" OR "attention" OR "impulsivity" OR "cognition" OR "education" OR "occupation". Results: Our search detected a total of 2,870 studies, from which we extracted 124 relevant studies from the literature on cannabis effects in the non-clinical population. Effects of cannabis on several behavioral sequelae including cognition, motivation, impulsivity, mood, anxiety, psychosis intelligence, and psychosocial functioning were identified. The preponderance of the evidence suggests that frequency of cannabis use, THC (but not CBD) content, age of onset, and cumulative cannabis exposure can all contribute to these adverse outcomes in individuals without a pre-existing medical condition or psychiatric disorder. The strongest evidence for the negative effects of cannabis are for psychosis and psychosocial functioning. Conclusions: Although more research is needed to determine risk factors for development of adverse behavioral sequelae of cannabis use, these findings underline the importance of understanding vulnerability to the adverse effects of cannabis, which has implications for prevention and treatment of problematic cannabis use.

A Comprehensive Examination of the Links between Cannabis Use and Motivation

Background: Cannabis use is widely perceived to produce an "amotivational syndrome" characterized by reduced desire to work or compete, passivity, and lower achievement orientation. The notion that cannabis diminishes motivation has been perpetuated in popular culture, despite the equivocal results of past research. Moreover, previous literature has largely failed to consider the potentially confounding influences of depression, other substance use, and personality, despite known relationships between these variables and cannabis use.Purpose: The purpose of this study was to elucidate the nature of the relationships between specific aspects of motivation and cannabis use/misuse. Moreover, we sought to determine whether depression, alcohol and other substance use, and/or personality could account for these relationships.Method: A total of 1,168 participants completed a survey comprising self-report measures of motivation (self-efficacy, apathy, goal orientation, reward-sensitivity, and behavioral inhibition/approach systems) and cannabis use/misuse (cannabis use status, cannabis use frequency, quantity, age of onset of cannabis use, symptoms of cannabis use disorder, problematic cannabis use).Results: The results revealed small (r < .30) but significant correlations between various aspects of cannabis use and motivation, which were largely accounted for by cannabis-related differences in depression, alcohol and other substance use, and personality. However, relationships between cannabis misuse and apathy remained statistically significant after controlling for confounds, indicating that individuals who misuse cannabis may demonstrate higher levels of apathy specifically.Conclusion: Collectively, these results suggest that differences in depression, substance use, and personality between cannabis users and non-users largely explain differences in motivation between these groups.

Effects of Adolescent Cannabis Use on Motivation and Depression: A Systematic Review

Purpose of review

This article reviews recent behavioral and neuroimaging studies to elucidate whether adolescent cannabis use is related to reduced motivation and increased risk of depression.

Recent findings

Recent work suggests that heavy adolescent cannabis use predicts poorer educational outcomes, often presumed to reflect reduced academic motivation, as well as increased levels of depressive symptoms. However, evidence of a link between cannabis use and general motivation was lacking. Factors such as concurrent alcohol and tobacco use, trajectories of cannabis use during adolescence, and cannabis-related changes in underlying neurocircuitry may impact associations among cannabis use, motivation, and depression.

Summary

Heavy adolescent cannabis use is associated with poorer educational outcomes and increased levels of depressive symptoms. The role of depression in how cannabis may affect motivation, broadly, is not yet clear, as most studies have not examined associations among all three constructs. Future work should explore possible overlap between cannabis effects on motivation and depression, and clarify the temporality of these associations.