fMRI of Stress in Smoking Behavior

Inclusion Criteria: 1. age 18-50 years inclusive; 2. able to read and write English; 3. for women, being in follicular phase of menstrual cycle; 5\) Tobacco dependent sample: smokes 10 or more cigarettes daily for the past year; Non-smokers, no tobacco consumption for more than one year and never having used tobacco daily. Exclusion Criteria: 1. any major neurological illness or injury and any current or prior clinically significant mental health (including PTSD) or substance use disorder (with possible exception of nicotine dependence) as determined by SCID interview; 2. use of any psychoactive medication within past four weeks; 3. any significant unstable medical condition such as asthma or heart disease for which increased cardiovascular reactivity during stress challenge might constitute a significant risk; 4. IQ\<70 based on past intelligence testing; 5. any metal in body that would pose a risk with MRI; and 6. claustrophobia that would interfere with MRI; 7. alcohol and drug use in the 72 hours prior to scanning, with the exception of tobacco; 8. pregnancy for women.