Cannabis Legalization in California Was Linked to Changes in Alcohol Use — But the Direction Depends on Age | Research

The takeaway

After California legalized recreational cannabis, heavy drinking rates gradually declined among younger adults (21–34) but showed some increases among older adults (65+), based on over 8 million primary care screenings.

Public health officials, policymakers evaluating cannabis legalization effects, and researchers studying substance use substitution patterns.

What the researchers found

Following cannabis legalization passage in 2016, rates of exceeding weekly alcohol limits and frequent heavy episodic drinking showed statistically significant gradual declines overall, but age-stratified analysis revealed the reductions were concentrated in adults 21–34, while adults 65+ showed some increases.

Why it matters

The substitution hypothesis — that legal cannabis might replace some alcohol use — appears to hold for younger adults but not older ones. This has implications for how we evaluate the public health impact of cannabis legalization across different demographics.

The numbers in context

Over 8 million screenings from 3.5 million unique patients. Significant gradual decline in exceeding weekly limits after legalization passage (slope change = -0.013, p < 0.001). Significant decline in frequent heavy episodic drinking (slope change = -0.015).

How the study worked

Interrupted time series analysis using ARIMA models examined monthly rates of positive alcohol screens from over 8 million screenings across Kaiser Permanente Northern California (2015–2019), evaluated at two intervention points: legalization passage (Nov 2016) and sales implementation (Jan 2018).

What this study cannot tell us

Observational data from one healthcare system in California may not generalize. Cannot confirm individuals actually used cannabis. Other temporal trends could explain changes. Screening data may not capture all drinking behavior.

How to read the evidence

Large-scale interrupted time series design with over 8 million screenings and rigorous ARIMA modeling, though observational limitations apply.

When this study was published

Published 2025, analyzing data from 2015–2019.

The bigger picture

The relationship between cannabis legalization and alcohol use is not one-size-fits-all. Age appears to be a key modifier, with younger adults potentially substituting cannabis for alcohol while older adults may add cannabis without reducing drinking.

Questions still open

Why do older adults respond differently to legalization than younger adults? Are younger adults substituting cannabis for alcohol, or are other factors driving the decline? Do these age-specific patterns persist in other states that legalized cannabis?

Common questions

Does cannabis legalization reduce alcohol problems?

For younger adults (21–34), this study suggests it may. But the effect varies by age — older adults (65+) did not show the same decline, and some measures increased. The relationship is nuanced.

Does this prove people are switching from alcohol to cannabis?

Not directly. The study shows alcohol screening rates changed after legalization, but it cannot confirm that individuals substituted cannabis for alcohol. Other societal trends may be involved.

Read the original research

Are cannabis policy changes associated with alcohol use patterns? Evidence for age-group differences based on primary care screening data.

Addiction (Abingdon, England), 120(11), 2282-2294

View on PubMed ↗Publisher’s paper ↗

Citation

Van Doren, Natalia; Chi, Felicia W; Young-Wolff, Kelly C; Satre, Derek D; Sterling, Stacy A. (2025). Are cannabis policy changes associated with alcohol use patterns? Evidence for age-group differences based on primary care screening data.. Addiction (Abingdon, England), 120(11), 2282-2294. https://doi.org/10.1111/add.70134