National cross-sectional survey of US adults to assess the reliability of current and lifetime cannabis smoking

Objective The objective is to examine the test-retest reliability and internal reliability of six self-report questions assessing both current (past 30 days) and lifetime cannabis smoking in an internet survey in the adult US population. Design Cross-sectional national survey. Participants Out of 957 US adults who completed a national 2020 survey administered through Ipsos KnowledgePanel, 557 completed a second survey ('reliability survey') aimed at assessing the test-retest and internal reliability of questions asking about current and lifetime cannabis smoking. The sample size used in the analysis for the six self-report questions varied and was dependent on respondents answering the questions in both the 2020 survey and the reliability survey. Primary outcome measure Test-retest and internal reliability of six self-report questions asking about current and lifetime cannabis smoking. Results Among respondents who had smoked cannabis in the past 30 days, 33.8% were aged 18-34, 29.7% were 35-49, 27.7% were 50-64 and 8.8% were 65 or older. Current cannabis smokers were primarily men (59.5%) and white (63.0%). Almost half of current cannabis smokers had a high school diploma or less followed by some college and a bachelor's degree or higher (45.7%, 30.6%, 23.8%, respectively). The question assessing number of days participants smoked cannabis in the past 30 days demonstrated good test-retest (r=0.87) and excellent internal reliability (alpha=0.94). The questions assessing the number of years, the most common form of use and the number of times participants smoked cannabis over their lifetime also demonstrated test-retest (r=0.77 (acceptable), r=0.75 (acceptable) and kappa=0.65 (substantial), respectively) and excellent-to-good internal reliability (alpha=0.91, alpha=0.87 and alpha=0.88, respectively). Conclusions We found simple questions assessing current and lifetime cannabis use to demonstrate both test-retest reliability and internal reliability. These questions can serve as a simple framework for clinicians to evaluate the frequency of cannabis smoking in their patients. Future work should examine if these simple frequency measures of smoking cannabis are associated with adverse health outcomes.