Scientifically studying the effects of marijuana has historically been fraught with inaccuracies and unempirical results. However, the studies seem to be pointing to a common thread: marijuana is associated with diminished motivation.
In a recent review, Volkow et al. (1) examined the effects of marijuana on motivation. Animal studies and preliminary human investigations have linked marijuana use with amotivation and apathy. When trained to perform a task, rhesus monkeys demonstrated reduced motivation for reward under the influence of marijuana. The same has been found in human subjects, as marijuana users showed decreased motivation for reward-related behavior. In addition, the amotivational state is negatively associated with reduced dopamine synthesis within the striatum in the brain, and marijuana users show a decreased response to dopaminergic stimuli, suggesting that the decreased production of and dampened sensitivity to dopamine (the neurotransmitter associated with rewards) underlies the lack of motivation in marijuana use.
Consistent with the above findings, Lane, Cherek, Pietras, and Steinberg (2) evaluated the effect of marijuana use on monetary motivation. Adolescents who smoked marijuana on a regular basis (nearly daily) and non-smokers completed two tasks, “work” and “non-work.” The “work” task required increasing response output from the participant and garnered more monetary compensation, compared to the “non-work” task which involved no response and less monetary compensation. Marijuana smokers were found to switch to the ‘non-work’ task earlier, and a higher percentage of their total compensation came from the “non-work” task, indicating reduced motivation. In another study, Cherek, Lane & Dougherty (4) found that marijuana users were not motivated when faced with a small monetary gain, although they were motivated when faced with a large monetary gain.
In relation to mental health, Musty and Kaback (3) studied the role of depression on the relationship between marijuana use and motivation. They found that both light (median of several times per month for 4.5 years) and heavy marijuana users (median of daily use for six years) with depressive symptoms were less likely to think that 1) their environmental stimuli are structured, predictable, and stable, 2) they have the resources to meet the demands of these stimuli, and 3) these demands are worth their engagement. Heavy users with depressive symptoms also reported lower needs to achieve compared to heavy users without depression and light users.
In conclusion, the current literature supports the ideas that marijuana use is associated with reduced motivation, and such amotivation is related to changes in dopaminergic production and response in the brain reward system. However, due to the scarcity of research, there is yet enough evidence to conclude that marijuana has a direct, causal link to a lack of motivation.
One possible method of treatment is neurofeedback, which can help balance the brain so that normal motivation can be restored. This usually involves targeted training in frontal lobe functioning. There is no known research literature to support this, however. Also, in my practice, I would insist that the use of marijuana be stopped in order to give the neurofeedback training a chance to work.
References
- Volker, N, Swanson, J, Evins, A, DeLisi, L, Meier, M, Gonzalez, R, Bloomfield, M, Curran, H, & Baler, R (2016). Effects of Cannabis Use on Human Behavior, Including Cognition, Motivation, and Psychosis: A Review. JAMAL Psychiatry, 73(3):292-297. https://www.yellowbrickprogram.com/ArticlePDF/Cannabis-and-Behavior-JAMA.pdf
- Lane, S, Cherek, D, Pietras, C, & Steinberg, J (2005). Performance of heavy marijuana-smoking adolescents on a laboratory measure of motivation.Addictive behaviors, 30(4), 815-828. https://www.researchgate.net/publication/7902788_Performance_of_heavy_marijuana-smoking_adolescents_on_laboratory_measure_of_motivation
- Musty, R & Kaback, L (1995). Relationships between motivation and depression in chronic marijuana users. Life Sciences, 56(23-24), 2151-2158. https://www.ncbi.nlm.nih.gov/pubmed/7776845
- Cherek, D, Lane, S, & Dougherty, D (2002). Possible amotivational effects following marijuana smoking under laboratory conditions.Experimental and Clinical Psychopharmacology, 10(1), 26. https://psycnet.apa.org/record/2002-00353-004
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