A new systematic review examining 329 studies found that marijuana legalization is consistently associated with reductions in marijuana-related enforcement, while researchers found no uniform increase in marijuana use among adolescents.
Published August 26 in Substance Use & Misuse, the review was conducted by researchers from COER University in India. Researchers analyzed studies published from 2020 through 2025 examining the public health, criminal justice and broader societal effects of marijuana legalization.
Researchers said the strongest and most consistent evidence involved criminal justice outcomes, with legalization linked to reduced marijuana-specific enforcement, particularly possession arrests.
Adult marijuana use, legal purchasing and perceived access generally increased following legalization, especially in jurisdictions where licensed retail markets expanded. However, researchers found that marijuana use among adolescents did not increase uniformly across the studies they reviewed.
The review did identify several areas of concern involving younger people, including lower perceptions of risk, more frequent use among some groups, accidental ingestion of marijuana products and increases in certain emergency-care and marijuana use disorder-related outcomes.
Researchers also found that legal marijuana markets did not necessarily eliminate illicit sales. Unregulated markets were more likely to persist when legal products were more expensive, difficult to access or otherwise unable to compete with illicit sellers.
The authors concluded that the effects of legalization depend heavily on how individual jurisdictions regulate their markets, including availability, commercialization, enforcement and public health safeguards.
“Legalization is best understood as a regulatory process,” researchers concluded.
