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

The takeaway

Early-onset cannabis users (before age 18) performed worse on the Iowa Gambling Task than late-onset users and non-users, showing decision-making driven more by short-term gains and less by loss avoidance.

Read this if you started using cannabis as a teenager and are curious about how age of onset might affect decision-making.

Early-onset users showed worse decision-making; late-onset users performed like non-users

What the researchers found

Researchers compared decision-making ability across three groups: 72 participants divided into early-onset cannabis users (who started before 18), late-onset users (who started at 18 or later), and non-using controls. They used a computerized version of the Iowa Gambling Task, where participants choose from card decks with varying risk-reward profiles.

Early-onset consumers performed significantly worse than both late-onset users and controls. When researchers applied a computational model to understand the decision-making process, they found that early-onset users were more influenced by the raw magnitude of gains and losses rather than their probability, and their choices were more determined by short-term results without adequate aversion to losses.

Late-onset users did not show the same decision-making deficits, performing similarly to non-users. This pattern suggests that the age at which cannabis use begins may be more important than cannabis use itself for long-term decision-making ability.

Why it matters

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.

The numbers in context

72 participants total: 19 women, 53 men. Three groups: early-onset users, late-onset users, non-users. Early-onset users showed significantly worse IGT performance. Computational modeling revealed early-onset users had less loss aversion and more recency bias in their decisions.

How the study worked

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.

What this study cannot tell us

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.

How to read the evidence

This is a small cross-sectional study with purposive sampling, providing preliminary evidence of an association between early cannabis onset and decision-making deficits.

When this study was published

Published in 2018. Research on cannabis onset age and neurocognitive outcomes continues to develop.

The bigger picture

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.

Questions still open

Do the decision-making deficits observed in early-onset users recover with prolonged abstinence? Are these deficits a cause or consequence of early cannabis use? Does the type or potency of cannabis matter for long-term decision-making outcomes?

Common questions

Does starting cannabis young permanently affect decision-making?

This study found worse decision-making in early-onset users but could not determine whether the effects are permanent. The cross-sectional design captured a snapshot rather than tracking changes over time. Recovery with abstinence was not assessed.

Does it matter when you start using cannabis?

This study found that people who started before 18 showed decision-making deficits, while those who started at 18 or later performed similarly to non-users. This suggests that age of onset may be more important than cannabis use itself for certain cognitive outcomes.

Read the original research

Age of onset of cannabis use and decision making under uncertainty.

PeerJ, 6, e5201

View on PubMed ↗Publisher’s paper ↗

Citation

Alameda-Bailén, Jose Ramón; Salguero-Alcañiz, Pilar; Merchán-Clavellino, Ana; Paíno-Quesada, Susana. (2018). Age of onset of cannabis use and decision making under uncertainty.. PeerJ, 6, e5201. https://doi.org/10.7717/peerj.5201