Does cannabis really affect motivation?

People under the influence of cannabis are often regarded as lazy, laid-back and apathetic. But is this a fair assessment? Cambridge University's Martine Skumlien has just published a study, in collaboration with UCL in the International Journal of Neuropsychopharmacology, comparing how frequent cannabis users fare against non users in a series of tasks designed to probe this.

Martine - There's this idea that cannabis will make you lazy and demotivated and apathetic. So think of like The Dude in The Big Lebowski, for example, that's basically what we sought to find out in this study. So we compared people who use cannabis and people who don't use cannabis on a few different assessments of reward and motivation. So they completed a questionnaire with questions like 'I have initiative', 'I get going during the day'. And then they also did a laboratory tasks where they could do these button presses to get chocolate or sweets. So kind of a measure of if you're willing to expend physical effort to get a reward.

Julia - And so what did you find then from these tasks?

Martine - Well, we basically found no difference between people who use cannabis and people who didn't. So really no evidence to support this stereotype of the like demotivated cannabis user.

Julia - So if it's not the drug that's causing this sort of stereotype, what do you think has perpetuated that?

Martine - That's a good question. And I'm not really sure. So I should point out that the people in our study were not under the influence of cannabis, so they were quote unquote 'sober' when they did the tasks. It could obviously be that people are slightly less motivated whilst they're high. So maybe that's why you get this trope. I think also anti-cannabis public safety adverts, particularly in the 90's, but today as well, really, really played up this trope, that cannabis is gonna make you super lazy and take away all of your ambition and you're going to fail at school. And so maybe it, it kind of comes from there as well.

Julia - Do you think that the idea that cannabis uses are apathetic could come from the fact that many people use cannabis as self-medication, if they have other mental health problems?

Martine - I think that could partly be the case. So it could be that cannabis has like an indirect effect through, say, depression or psychosis or something like that. Or, for instance, if you have people who have very strong cannabis use disorder, maybe they would show a stronger effect, but this is still the minority of users and obviously most people who have depression, presumably don't use cannabis. So I don't think it can, it can be the whole story.

Julia - So you think the findings from this research could have any baring on legal standards towards cannabis in the UK?

Martine - So one of the things that I hear quite a lot in this debate is that people are worried about adolescents particularly. So if we legalize cannabis, then adolescents are gonna use more cannabis and adolescents maybe are more vulnerable to harmful effects of cannabis. So we also looked at this in this study. So we did compare cannabis users who were adults and cannabis users who were adolescents and basically we're not finding any adolescent vulnerability effect, though so I guess in that sense our results are somewhat encouraging. Although we have only looked at motivation, there are obviously a bunch of other psychological and cognitive outcomes that people need to assess. And I should just add that obviously we're scientists so our mission is to find the answer and then it's up to other people and policy makers to decide what to do with those.