One joint of marijuana makes you lazy… but only for a short time

We have conducted two studies to investigate the claim that marijuana leads to decreased motivation. When we gave people the equivalent of a spliff of cannabis in controlled conditions, they were less willing to do work for money. They are less motivated than usual. We also compared cannabis addicts with a control group of non-cannabis drug consumers. When neither group had taken drugs for 12 hours or more, we found no difference in the motivation to earn money.

In the short term, our results show that cannabis smoking reduces motivation. Long-term cannabis usage may not affect your motivation if you quit smoking it after 12 hours.

‘Amotivational syndrome’

As cannabis became popular as a recreational drug in the 1950s and 60s, reports on cannabis’s “amotivational disorder” began to appear. Clinicians said, “Regular marijuana [sic] consumption may contribute to the development more passive, inward-turning, amotivational character traits”. These reports were based on the observation of cannabis users’ laziness. To investigate the short- and long-term impacts of cannabis, more research is needed.

Early research on the short-term effect of cannabis on motivation found that it was both motivating as well as demotivating. These studies were not well-controlled and often had a bizarre design. One involved getting people high and having them make stools in the shortest time possible. In a recent study, cannabis was given to participants in a controlled experiment. The results showed that the people were less motivated by money. This experiment was conducted on a small group of only five participants.

In our new study, we used a double-blinded, placebo-controlled design to examine the effect of cannabis on motivation toward money in a larger group of 17 participants. Participants inhaled cannabis vapor through a balloon on two occasions and placebo cannabis vapor on the other. They then completed a task to determine their motivation to earn money. The participants received cash at the end. They could choose to do low-effort or high-effort options in each trial to make varying amounts of money. In the low-effort option, you had to press the spacebar 30 times within seven seconds in order to win 50p. The high-effort version required 100 spacebar presses within 21 seconds to receive rewards that ranged from 80p up to PS2.

One hundred spacebar presses equals more money. BaLL LunLa/

Cannabis users were less likely to select the option requiring high effort. Volunteers on placebo selected the high-effort option 50% of the time to receive a PS2 prize, while volunteers on cannabis chose it only 42% of the time. They were less motivated to earn money when they were high. It has long been believed that being high makes one lazy. However, this is the first time that it can be reliably shown using a large enough sample size.

No difference

It’s more difficult to answer the question of whether long-term cannabis usage makes people demotivated even when they are not high. We can’t do randomized controlled studies in which one group of people receives cannabis for 10 years while the other group gets a placebo. This would be, of course, unethical. We must, therefore, rely on observational research, which examines associations between cannabis consumption levels and motivation. Some research has failed to find a relationship between marijuana use and altered motivation. However, in one study, earlier consumption of cannabis predicted later anhedonia.

In an observational study, we compared 20 people with a cannabis addiction with a control group consisting of 20 non-addicted cannabis users. The control group also used cocaine and MDMA in a similar quantity to the cannabis group. The participants in this study completed the same task as the previous one after being free of drugs for 12 hours (apart from caffeine and tobacco). There was no difference in the willingness of either group to work for money. This indicates that cannabis use over a long period may not affect motivation 12 hours after abstinence.

This study has some limitations. The sample sizes were very small. The study was cross-sectional, so the participants were only studied at one time. A longitudinal study design would have been better, as it would have measured motivation and cannabis consumption at various points in the participants’ lives. It would have been possible to understand better how cannabis use affects motivation in the future. To draw more solid conclusions, longitudinal research is required.

What are the implications of our findings for a typical cannabis consumer? We’ve shown that, after years of hearing that being high made you lazy, it is true. It doesn’t eliminate your motivation, but it does make you more apathetic. On the plus side, long-term cannabis usage may not affect your motivation as some people claim. Just make sure you put down your joint for a little while.

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