As the third most commonly used drug worldwide, University of Melbourne researchers wanted to establish the ramifications of long-term use.

Researcher Gezelle Dali told ACM they found people who used cannabis from earlier in life were less likely to correct their mistakes, even if they knew they had made them.

"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," she said.

"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."

Ms Dali said the effect of cannabis on the brain could manifest as a behavioural impairment, demonstrated in the study through poorer error processing.

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Chronic cannabis use and error awareness: The effect on learning from errors studied 70 Australians, about half which were chronic cannabis users.

Ms Dali said the study was also motivated by a lack of research into the ramifications of cannabis use, despite it's prevalence.

The study didn't find a difference between cannabis and non-cannabis users. It only found the younger they were when they picked up the cannabis habit, the poorer their error processing was.