Race and Drug Use Over Time Related to Stress Hormones

Understanding the relationship between drug use and the stress responsive hormone cortisol may help identify those at greatest risk for substance use disorder.  Addictive drugs trigger a stress-response across a wide range of physiological systems (Lovallo, 2006).  For some people drug use may be a stressor capable of shifting psychobiology into hypo-responsiveness. The combination of exposure to drugs and blunted stress-response leads to further drug use.  The impact of stress exposure depends in part on previous stress exposure. The Adaptive Calibration Model (Del Guidice, Ellis, & Shirtcliff, 2011; Skinner, et al 2011) suggests that race differences in exposure to stressors may lead to race differences in how drug use is related to cortisol regulation. This study examines the relationship of drug use in adolescence and early adulthood with diurnal cortisol at age 20.

Participants include black (n=162) and white teens (n=168) recruited in the 8^th grade in 2001/02 and followed to age 22. Early drug use was reported in 10^thgrade (sum of alcohol, cigarettes, and marijuana), concurrent use at age 20, and later use at age 22. Hierarchical linear models estimated intercept (waking level) and slope (decline over the day) for salivary cortisol assayed at 4 times/ day on 3 days.  Main effects for drug use and interactions with race were tested controlling for income and gender.

Results revealed significant interactions on cortisol waking cortisol for adolescent drug use such that the effect was not significant for whites (B=-.01, p=.24) and predicted higher waking levels for blacks (B=.05, p< .01). No effect was found on slope. 

Concurrent cigarette use (age 20) was not significantly related to waking cortisol. For whites smoking was associated with flatter slope (B=.03, p< .01) but not for blacks (B=-.01, p=.13). Concurrent alcohol use was related to lower waking cortisol regardless of race (B=-.12, p=.02). Race moderation on the slope (F=7.46, df=2,  596, p< .01) indicted flatter slopes for blacks than whites, and this race difference was more pronounced among drinkers than non-drinkers. Concurrent marijuana use was not related to waking cortisol or slope.

 Age 20 waking cortisol was related to more frequent alcohol (B=-.05, p < .01) and marijuana use (B=-.03, p=.01) 2 years (30 day frequency@ age22) regardless of race. Lower waking level was associated with more cigarette use at age 22 for whites (B=-.05, p=.04) but not blacks (B=.03, p=.29).  Diurnal slope at age 20 was not related to later drug use.

Lower waking cortisol and flatter slope is associated with concurrent and later drug use in early adulthood with some race moderation. Implications for prevention will be discussed in the context of stress exposure and the Adaptive Calibration Model.