Cognitive Outcomes among Cannabis Users with and without a History of Polysubstance Use

Abstract

Abstract Despite substantial efforts to understand the impact of cannabis use on cognition, the potential effects remain debated. More research focusing on how cannabis is used, specifically around the quantity used and cannabis co-use with other substances, is needed to better understand the outcomes of cannabis use. Current cannabis users were asked to report all substance use history and current daily grams of cannabis use, and they completed a battery of cognitive assessments: BART-impulsivity/risk-taking, Face/Name-memory, Iowa Gambling-risk aversion and decision making, Stroop-attention, Tower of London-planning, and Trier Social Stress Task. Cognitive measures and stress response were compared between two groups of cannabis users: those with a polysubstance use history (CUP, 47%) and those without (CU, 53%), using linear or Poisson regression models. Models were also fit to assess the associations between daily grams of cannabis, cognitive measures, and stress response. Between groups, CUP scored 2.41 points higher ( p = 0.02) in the cognitive domain of planning than CU. Associations with quantity of cannabis use were observed for stress response (cortisol) and cognitive domains: impulsivity, memory, and risk aversion. For each 1-gram increase in daily cannabis use, cortisol changes following stress were 0.02 mcg/dL smaller ( p = 0.01); following a recovery period, cortisol changes were 0.02 mcg/dL larger ( p = 0.02). For cognitive domains, impulsivity scores were 2.94 points lower ( p = 0.03), memory scores were 18.7% lower ( p = 0.03), and risk aversion scores were 2.34 points higher ( p = 0.05) for each 1-gram increase in daily cannabis use. We found minimal differences between groups and unexpected differences in stress response and cognition based on the quantity of cannabis use. Given our sample size and the temporal aspect of polysubstance use in this sample, more work is needed to understand the impacts of the quantity of cannabis and polysubstance use on outcomes in cannabis users.

In the evidence

This study is part of the evidence base for a synthesis in the library. Here is how each one recorded it.

• State of the evidence: Cannabis ↕Mixed

  Polysubstance users scored 2.41 points higher on planning than cannabis-only users, while greater daily cannabis quantity was associated with blunted stress cortisol response, lower impulsivity and memory scores, and higher risk aversion.

  Synthesized October 19, 2026

Comparable studies

Other observational and cohort studies on cannabis, most cited first.