Prevalence of cannabis use among individuals with a history of cancer in the United States.

Cannabis (marijuana) use is increasing in the United States, but we do not have much information on the relationship between cannabis use and cancer. We studied information from a representative group of people and found that younger patients generally reported more past and/or recent cannabis use if they had been diagnosed with cancer whereas older individuals did not. Beliefs about cannabis risk and accessibility differed by age. Clinical trials to study cannabis should account for patient age, and accurate information about cannabis should be provided to help patients with cancer make decisions about cannabis use.