Methylphenidate Studies for Drug Abuse Vulnerability Molecular Genentics

Study Summary

Background: * Research has shown that several human genes have been associated with vulnerability to substance abuse and dependence. However, little is known about how people with these genetic tendencies react to drugs in controlled settings. * Methylphenidate, also known as Ritalin, is commonly prescribed for a number of conditions, including attention deficit disorder. Because methylphenidate is widely used in studies of brain chemistry and behavior and has relatively low risks associated with it use, researchers are interested in seeing how it affects the thinking processes of people with apparent genetic vulnerability to drug abuse. Objectives: \- To evaluate whether individuals with apparent genetic vulnerability to drug abuse react differently to methylphenidate than people who do not have this vulnerability. Eligibility: \- Individuals at least 18 years of age or older who have participated in the NIDA protocol Allelic Linkage in Substance Abuse. Design: * Participants will be asked to avoid using a number of over-the-counter medications, including antihistamines, cough medicines, and nasal decongestants, for 24 hours before the study day. Participants will also be asked to avoid consuming caffeinated beverages, nicotine or tobacco products, or alcohol on the morning of the day of the study, and will provide a urine sample at the start of the study to be tested for chemicals that may interfere with the study. * Because of the nature of the study drug, participants will not be allowed to drive to the clinical center on the day of the study. (Return transportation will be arranged.) * At the start of the study, participants will take two tablets (each 1 hour apart), and will not be told whether the tablets are the study drug or a placebo. * Participants will give regular answers to questions about mood and thinking processes on a computer for approximately 5 hours. Blood samples will be taken during this part of the study.