Impact of lifetime violence exposure on age of substance use initiation in context of intrauterine exposures

In the U.S. 17% of children age 12-17 witness and 39% are victims of violence, while 1% experience intrauterine cocaine exposure (IUCE). Although exposure to violence (EV) has been shown retrospectively to be a risk factor for earlier age of substance initiation, prospective data are limited, particularly in the context of intrauterine exposures. 149 adolescents involved from birth in a longitudinal study examining the effects of intrauterine cocaine exposure (IUCE) were evaluated to age 16 for lifetime (EV) using the Violence Exposure Scale for Children-Revised (VEX-R). Participant age of initiation of illicit substance use was determined by audio computer assisted interviews and urine assays. The impact of EV was analyzed as a time dependent predictor of age of substance initiation in Cox proportional hazard models, controlling for level of intrauterine exposures to cocaine, marijuana, alcohol, and tobacco and relevant demographic variables.

In this adjusted model, having VEX-R scores in the third or fourth quartiles compared to the first had a moderate-to-strong association with earlier age of initiation (third quartile: HR=2.29, 95% CI: 1.1, 4.7 p=0.03; fourth quartile: HR=3.44; 95% CI: 1.7, 6.9, p=0.0006). A moderate positive association between IUCE and earlier age-at-initiation was also found, with hazard ratios of 2.19 for heavier IUCE exposure vs. unexposed (95% C.I.: 1.10, 4.36, p=0.03) and 1.69 for lighter IUCE exposure vs. unexposed (95% C.I.: 0.95, 3.03, p=0.07).

Although both IUCE and EV predict earlier age of substance initiation, prospectively ascertained EV is a stronger predictor and more prevalent risk factor.