Prevalence and Correlates of Simultaneous and Separate 30-Day Use of Tobacco and Cannabis: Results from the California Adult Tobacco Survey.

: There is limited information on separate use and simultaneous use of tobacco and cannabis products, particularly for new electronic nicotine delivery systems (ENDS). This study presents detailed information about the prevalence and correlates of individual use, separate use, and simultaneous use of tobacco and cannabis in California, the first state to allow medical marijuana in the US. It specifically distinguishes between simultaneous use (both substances used in the same occasion) and separate use (both products used, but not simultaneously). : Participants in the 2016 California Adult Tobacco Survey ( = 3,058; age range 18-64 years) completed online surveys between February and March 2016 that assessed tobacco and cannabis use in the past 30 days. : Participants' use of tobacco (15% cigarettes) was higher than use of ENDS (6%) or cannabis (10%); the overall rate of separate use was 6% and the overall rate of simultaneous use was 3%. Correlates of tobacco use included lower levels of education and income. Correlates of simultaneous tobacco and cannabis use included being unemployed or having a disability. : This survey of California residents suggests how use patterns change in states that legalize medical marijuana prior to recreational cannabis, although it may underestimate prevalence due to reliance on self-reported use. Persons who were unemployed and persons with disabilities were at higher risk for simultaneous use of tobacco and cannabis. These findings suggest that prevention and cessation interventions intended to target simultaneous use should address these populations, as well as adolescents and young adults.