Environmental factors that have been consistently associated with the propensity to self-administer drugs include structural factors (eg, low socioeconomic status and associated lack of social support systems), proximal factors (eg, parental drug use and dependence, as per the DSM-IV, poor quality of parenting, parental depression, and sibling and peer influences), and more distal factors (eg, drug availability, school, neighbourhood characteristics, advertising, and the media).177,178 Stress is also a common feature that increases the risk for drug abuse. The mechanisms that are responsible for stress-induced increases in vulnerability to drug use and relapse in those who are addicted are not yet well understood, but evidence suggests that the stress-responsive neuropeptide CRF is involved through its effects in the amygdala and hypothalamic-pituitary-adrenal axis.20
