The consequences of legal access to medical marijuana for individuals' well-being are controversially assessed. We contribute to the discussion by evaluating the impact of the introduction of medical marijuana laws across US states on self-reported mental health considering different motives for cannabis consumption. Our analysis is based on BRFSS survey data from close to eight million respondents between 1993 and 2018 that we combine with information from the NSDUH to estimate individual consumption propensities. We find that eased access to marijuana through medical marijuana laws reduce the reported number of days with poor mental health for individuals with a high propensity to consume marijuana for medical purposes and for those individuals who likely suffer from frequent pain.