Learning about personal genetic risk for cannabis-psychosis made people more likely to avoid marijuana

Participants told they had a genetic predisposition for marijuana to increase schizophrenia risk rated the likelihood and importance of avoiding marijuana as significantly higher than controls. In the nationally representative sample, this effect was strongest among those who had previously used marijuana. Conversely, being told one lacked such a predisposition tended to lower avoidance intentions, raising concerns about a "genetic license" effect.

Two randomized experiments. Experiment 1: 801 US young adults from Mechanical Turk. Experiment 2: 800 nationally representative US adults aged 18-30. Participants randomized to three conditions: genetic predisposition present, absent, or no genetic testing (control). Measured intentions to avoid marijuana.

As genetic testing becomes more common, understanding how personalized risk information affects substance use behavior is critical. This study suggests genetic cannabis-psychosis risk information could be a powerful prevention tool, but the "no predisposition" condition raises ethical concerns.

The finding that prior marijuana users were most responsive to genetic risk information is encouraging for targeted prevention. However, the risk that genetic "all-clear" results could reduce caution (the genetic license effect) needs careful consideration before implementing such testing.

Hypothetical scenarios, not actual genetic tests. Self-reported intentions may not predict behavior. Mechanical Turk sample in Experiment 1 may not be representative. Short-term measurement only.