Defining Neurobiological Links Between Substance Use and Mental Illness

Background: Nicotine dependence leads to about 480,000 deaths every year in the United States. People with major depressive disorder (MDD) are twice as likely to use nicotine compared to the general population. They have greater withdrawal symptoms and are more likely to relapse after quitting compared with smokers without MDD. More research is needed on how nicotine affects brain function in those with MDD. Objective: To understand how nicotine affects symptoms of depression and related brain function. Eligibility: People aged 18 to 60 years, at the time of consent, with and without MDD who do not smoke cigarettes or use other nicotine products. Design: Participants will have 2 or 3 study visits over 1 year. Participants will have 2 MRI scans no less than 4 days apart. Each scan visit will last 5 to 7 hours. At each scan, they will have urine and breath tests to screen for recent use of alcohol, nicotine, and illegal drugs. Before each scan, they will take 1 of 2 medications: nicotine or placebo. Participants will receive each medication once. They will not know which medication they are receiving at each scan. For each MRI scan, they will lie on a table that slides into a cylinder. Sometimes they will be asked to lie still. Sometimes they will complete tasks on a computer. Tasks may include identifying colors or playing games to win money. Each scan will take about 2 hours. Participants will answer questions about their thoughts, feelings, and behaviors before and after each scan. They will have a blood test after each scan.