Among inner-city youth, trajectories of increasing marijuana use from adolescence to adulthood were associated with over three times the odds of engaging in violence involving weapons.
Read this if you want to understand the research linking marijuana use trajectories to violent behavior in urban settings.
3.37x odds of weapon violence in the increasing marijuana use trajectory
What the researchers found
In a longitudinal study of 838 inner-city African American and Puerto Rican participants, researchers identified distinct trajectories of marijuana use from adolescence to adulthood and examined their association with violent behavior. Compared to the no/low use trajectory, the increasing marijuana use trajectory was associated with 3.37 times the odds of engaging in violence involving weapons (shooting or hitting someone).
The moderate use trajectory (AOR = 1.98) and even the "quitter" trajectory (AOR = 1.70) were also associated with increased odds of weapon-related violence compared to no/low use. The analyses controlled for other predictors of violent behavior.
Why it matters
Understanding the association between marijuana use patterns and violent behavior has implications for both public health prevention and criminal justice approaches. The finding that even "quitter" trajectories showed elevated violence risk suggests that exposure history matters beyond current use.
The numbers in context
838 participants. Increasing use trajectory: AOR = 3.37 (P < .001). Moderate use trajectory: AOR = 1.98 (P < .01). Quitter trajectory: AOR = 1.70 (P < .05). All compared to no/low use.
How the study worked
Longitudinal study following 838 inner-city African American and Puerto Rican participants. Growth mixture modeling identified marijuana use trajectories from adolescence to adulthood. Logistic regression examined associations between trajectory group membership and weapon-related violence.
What this study cannot tell us
Observational design cannot establish causation. The specific inner-city, minority population limits generalizability. Weapon violence is rare and affected by many contextual factors. Self-reported marijuana use and violence may be subject to reporting bias. Confounders related to socioeconomic conditions and neighborhood exposure were not fully captured.
How to read the evidence
Longitudinal trajectory analysis with appropriate statistical methods, though limited by observational design and specific population.
When this study was published
Published in 2014.
The bigger picture
This study does not establish that marijuana causes violence. The association likely reflects shared risk factors in inner-city environments, including poverty, exposure to violence, deviant peer networks, and limited educational opportunity. However, the dose-response pattern (heavier use trajectories = stronger association) warrants attention.
Questions still open
- Would these associations hold in different socioeconomic and demographic contexts? Does marijuana use directly increase aggression, or do shared environmental risk factors explain the association? Why did even the "quitter" trajectory show elevated risk?
Common questions
Does marijuana cause violent behavior?
Did quitting marijuana reduce violence risk?
Read the original research
Developmental trajectories of marijuana use from adolescence to adulthood: relationship with using weapons including guns.
Aggressive behavior, 40(3), 229-37
Citation
Brook, Judith S; Lee, Jung Yeon; Finch, Stephen J; Brook, David W. (2014). Developmental trajectories of marijuana use from adolescence to adulthood: relationship with using weapons including guns.. Aggressive behavior, 40(3), 229-37. https://doi.org/10.1002/ab.21520
Explore the wider topic
- How to Talk to Your Teenager About Weed (Without Losing Them)
- My Kid's Friends Smoke Weed: A Parent's Guide
- I Smoke Weed But Don't Want My Kids To: Navigating the Hypocrisy
- Quitting Weed as a Parent: Why It Is the Hardest and Most Important Quit
- Quitting Weed as a Teen or Young Adult
- My Kid Is Smoking Weed: A Parent's Guide