Early Cannabis Use May Affect How We Learn From Mistakes, Study Suggests

People who begin using cannabis at a young age may be worse at correcting their past mistakes, a new study suggests.

Published in PLOS One, the study used a routine behavioral test to measure how cannabis users and non-users would react to making errors. While they found no significant differences between the cannabis users and the control group, the University of Melbourne researchers did find that those who had been using cannabis from a young age were generally worse at correcting the errors that they were making, even if they recognized that they had made a mistake, compared to other cannabis users.

These findings would suggest that cannabis use may not be so tightly linked to error processing as once thought. However, the researchers believe their findings also highlight the general lack of research and understanding into how specific aspects of cannabis use – such as a young age of onset or frequent use – might affect performance and behavior.

How do we measure learning from mistakes?

In this trial, researchers recruited 36 cannabis users and 34 control participants from the University of Melbourne campus network, all aged between 18 to 44 years old. Being a cannabis user was defined as having used cannabis on at least a weekly basis for the past year, although it was noted that roughly half of the cannabis users enrolled in the study did report near-daily use.

The participants were first asked to complete a set of questionnaires aimed at characterizing each individual’s cannabis use habits, use of alcohol and other substances, physical health, and mental wellbeing.

Once these initial questionnaires were complete, the participants each took part in a “Go/No-Go” task, which was designed to assess how aware people are of their errors and how well they correct following an error.

The Go/No-Go task is a standard psychological test normally used to measure impulse control and inhibition. In a typical test, the participant is asked to perform an action when exposed to a certain stimulus (press a button when you see a certain prompt, for instance) and to not perform that action if exposed to a different stimulus (do not press the button if there is a different unique prompt).

In the present study, the cannabis users and control group members were shown a series of alphabet letters on a screen, each letter being flashed up on the screen one at a time. If the letter they saw was different to the previous letter, they were told to press “button 1”. If consecutive letters were shown, they were asked to press no buttons. In the event that the study participant made a mistake, they were told to press “button 2” on the following screen in order to acknowledge their mistake.

By analyzing these responses, the researchers were able to detect mistakes as well as whether the individual was aware of the mistake. By assessing their subsequent behavior when consecutive letters appeared again later in the task, the researchers could also see whether individuals would correct their previous mistakes or not.

Early onset cannabis use may impair learning and error correction

Contrary to the researchers’ initial hypothesis, they found no significant differences in error awareness when comparing the Go/No-Go task performances between the cannabis users and the control group. They also found no differences when looking at the relationship between accuracy of responses, or the reaction time needed for a response, when comparing the groups.

However, they did find that those reporting an earlier onset age of cannabis use were less likely to correct their earlier mistakes, even if they had been aware of making them. This was also true for cannabis users who scored higher on the “cannabis use index”, which was scored by the researchers based on reported cannabis use frequencies and responses to the cannabis use disorder and substance use questionnaires.

While the researchers did not detect any significant differences between the cannabis users and non-users, this within-group difference in error correction among cannabis users may have interesting implications.

“A lot of work has shown that there is some effect of age of onset, so the earlier that they start using cannabis the more likely they are to show impaired performance,” Gazelle Dali, the study’s lead researcher, recently told the Canberra Times.

“That is likely to be a function of the fact that when you’re young, your brain is still developing – it doesn’t stop developing until you’re about 25 years old.”

Previous studies have suggested that impaired error awareness in drug users may play a role in their continued drug use, as they could be less sensitive to the outcomes of their use. Compromised error processing in those with a substance use disorder has also been found to potentially interfere with users’ treatment retention and their ability to engage in intervention programs.

While error awareness specifically did not seem to be impacted here, the researchers do note that error processing in chronic cannabis users has not yet been extensively studied. In light of this previous research and new findings, the researchers say that additional research and systematic testing would be warranted.