People who started using cannabis as teenagers made worse decisions in a gambling task

This was a cross-sectional study of 72 participants (19 women, 53 men) divided into three groups via purposive sampling: early-onset cannabis consumers, late-onset consumers, and non-consumer controls. Decision-making was assessed using the "Cartas" program (computerized Iowa Gambling Task) in both direct and inverse versions. The Prospect Valence Learning computational model was applied to characterize decision-making along four dimensions: utility, loss aversion, recency, and consistency.

Decision-making is a fundamental executive function that affects everything from financial choices to risk behavior. If starting cannabis before the brain finishes developing (around age 25) specifically impairs this capacity, it provides a concrete reason for prevention efforts to focus on delaying the age of first use rather than simply preventing all use.

This study adds to a growing body of evidence suggesting that cannabis exposure during adolescence, when the prefrontal cortex is still developing, has different consequences than adult-onset use. The decision-making deficits observed align with what we know about prefrontal cortex function and its protracted development through the mid-twenties.

The sample was small at 72 participants, and the cross-sectional design cannot determine whether pre-existing decision-making differences led to earlier cannabis use rather than the reverse. The study did not control for concurrent use of other substances. Purposive rather than random sampling limits generalizability.