Frequency of cannabis use among primary care patients in Washington State.

This is the Results Article for CTN-0065.

Over 12% of U.S. adults report past-year cannabis use, and among those who use daily, 25% or more have a cannabis use disorder. Use is increasing as legal access expands, yet cannabis use is not routinely assessed in primary care, and little is known about use among primary care patients and relevant demographic and behavioral health subgroups. This study, from NIDA Clinical Trials Network protocol CTN-0065 (Evaluation of Drug Screening Implementation in Primary Care), describes the prevalence and frequency of past-year cannabis use among primary care patients assessed for use during a primary care visit.

This observational cohort study included adults who made a visit to primary care clinics with annual behavioral health screening, including a single-item question about frequency past-year cannabis use (March 2015-February 2016; n=29,857). Depression, alcohol, and other drug use were also assessed by behavioral health screening. Screening results, tobacco use, and diagnoses for past-year behavioral health conditions (e.g. mental health and substance use disorders) were obtained from EHRs.

Among patients who completed the cannabis use question (n=22,095; 74% of eligible patients), 15.3% (14.8-15.8%) reported any past-year use: 12.2% (11.8-12.6%) less than daily, and 3.1% (2.9-3.3%) daily. Among 2228 patients age 18-29 years, 36% (34-38%) reported any cannabis use and 8.1% (7-9.3%) daily use. Daily cannabis use was common among men age 18-29 years who used tobacco or screened positive for depression: 25.5% (18.8-32.1%) and 31.7% (23.3-50%) respectively.

Conclusions: This study of the prevalence and frequency of cannabis use among primary care patients, in a state with legalized use, found that most primary care patients who completed recommended routine behavioral health screening (e.g., depression and alcohol) also completed a question about past-year cannabis use. In addition, while 15% of all primary care patients reported any past-year cannabis use, the prevalence was much higher in important patient subgroups. Most notably, more than 1 in 4 younger men who used tobacco or screened positive for depression reported high-risk daily cannabis use. Routinely asking about cannabis use could promote recognition of patients who may benefit from primary care discussions about their cannabis use.