Longitudinal associations between susceptibility to tobacco use and the onset of other substances among U.S. youth.

We examined whether tobacco susceptibility at Wave (W) 1 (2013-2014) predicts the onset of tobacco and other substances at W2 (2014-2015) among 5325 U.S. youth (12-17 years) never substance users at W1 in the Population Assessment of Tobacco and Health (PATH) Study. Tobacco susceptibility was based on curiosity, use intentions, and response to a best friend's offer to use. Onset of use included past 12-month use of a specific substance or group of substances at W2 among those who had never used any substance at W1. Approximately, 31.3% of W1 youth were susceptible to tobacco use. W2 onset was 8.2% (SE = 0.4) for alcohol exclusively, 5.0% (SE = 0.4) for polysubstance including tobacco, 4.4% (SE = 0.3) for tobacco exclusively, 3.1% (SE = 0.3) for other drugs (misused prescription stimulants and painkillers, cocaine, other stimulants, heroin, inhalants, solvents and hallucinogens) exclusively, 1.4% (SE = 0.2) for polysubstance excluding tobacco, and 0.9% (SE = 0.1) for marijuana exclusively. Tobacco-susceptible compared with non-tobacco susceptible youth had higher odds of onset of exclusive tobacco use (AOR: 2.4; 95% CI: 1.7, 3.3), exclusive alcohol use (AOR: 1.5; 95% CI: 1.2, 1.8), and polysubstance use (AOR: 3.9; 95% CI: 2.8, 5.6 including tobacco and AOR: 1.8; 95% CI: 1.1, 3.0 excluding tobacco) compared with W2 never substance use. In this national study, tobacco susceptibility identified U.S. youth at risk for onset of tobacco and other substances, perhaps reflecting common etiology and clustering of substance use in youth. Identifying and preventing tobacco-susceptible youth from progressing to using addictive substances must remain a public health priority.