Digital media use and subsequent cannabis and tobacco product use initiation among adolescents.

Background: Digital media engagement, such as browsing the internet or social media posting, may be associated with cannabis and tobacco product use initiation among adolescents. Whether certain digital media exposure confers greater - or reduced - risk for specific cannabis or tobacco products is unknown.

Methods: Adolescents completed surveys on digital media and substance use every 6 months from 2015 to 2017 (4 waves). Self-reported digital media use (14 items) was classified into six subcategories (e.g., "social media posting," "reading news/articles & browsing photos"). Random-effect repeated-measures regression models examined the association of exposure to each digital media subcategory with subsequent cannabis or tobacco product use initiation in the next 6 months, among baseline cannabis and tobacco never-users (n = 1841; n = 1558, respectively).

Results: High frequency digital media use (multiple times/day) of "social media posting" (vs. no high frequency use; OR = 1.95; 95%CI:1.20-3.17) and "checking in" (OR = 1.71; 95%CI:1.23-2.38) was associated with greater odds of any cannabis product use initiation 6 months later. "Reading news/articles & browsing photos" was associated with decreased odds of initiation (OR = 0.52; 95%CI:0.34-0.79). "Checking in" and "reading news/articles & browsing photos" were similarly associated with any tobacco use initiation. "Chatting and shopping" was associated with greater odds (OR = 4.63; 95%CI:1.53-14.06) of e-cigarette initiation, but not of other product use initiation.

Conclusions: Some subcategories of digital media use conferred increased odds, others conferred reduced odds, and others were not associated with cannabis and tobacco use initiation. Research exploring mechanisms that put users of specific digital media at greater risk for substance use initiation is warranted.