Stress level before self-reported stress (a), smoking (b), drug use (c), and drug craving (e) events in Study 1. Stress level before self-reported smoking (d) and drinking (f) events in Study 2. Vertical dashed line shows the time of the event report, and horizontal bold line shows average daily stress level. Figure (a) shows that the stress level in minutes preceding a voluntary self-report of stress event is higher than average daily stress. Also, stress level in minutes preceding smoking is relatively higher than average daily stress.