Why people with attention-deficit/hyperactivity disorder (ADHD) are at greater risk of substance dependence, particularly methamphetamine dependence, and have greater difficulty overcoming their addiction is the subject of a new study by researchers at the UC Davis MIND Institute.
Earlier research has established that individuals with ADHD are at greater risk of substance abuse and of becoming dependent upon drugs. However, the reasons for the tendency are not well understood, the researchers said. Stimulants such as methylphenidate (Ritalin) or amphetamine (Adderall) are broadly prescribed for children and adults with ADHD.
"Methamphetamine abusers with ADHD often say that abusing methamphetamine helps calm them down and helps them to maintain focus," said Catherine Fassbender, a researcher with the MIND Institute, Imaging Research Center and Department of Psychiatry and Behavioral Sciences. "This may be a reinforcing factor in their continuing to abuse meth. Of course, there is a very big difference between taking a prescription medication and substance abuse."
Fassbender and her colleagues are examining how the cognitive deficits among people with ADHD may contribute to their being at greater risk of substance abuse. The study specifically looks at whether having the condition makes it difficult for people to realize that they're making an error in behavior.
"Cognitive control and insight into one's behavior are essential to optimal decision making and resisting impulses to engage in risky behaviors, such as substance abuse," Fassbender said. "We believe that impaired cognitive control contributes to developing and maintaining substance dependence, as well as to transitioning from recreational use to dependence or addiction."
To test that hypothesis, Fassbender and her colleagues are examining whether people with ADHD have difficulty detecting their own performance errors on a computerized laboratory test and using that information to optimize their performance. The study will compare people who do not have ADHD; people who do have ADHD; people who abuse methamphetamine; and people who both have ADHD and abuse methamphetamine.
The study participants' brain activity then will be examined for differences using functional magnetic resonance imaging (fMRI).
"The areas of the brain that activate when an addict is exposed to environmental cues that remind them of drug use are similar to regions that are involved when they are engaging in complex cognitive activities. Decision making about drugs could overload this cognitive control system and place you at greater risk of relapse," Fassbender said.
"This study is so important because it gives us the potential to identify targets that we can address to prevent and treat substance abuse in ADHD," said collaborator Julie Schweitzer, associate professor of psychiatry and behavioral sciences and director of the UC Davis ADHD Clinic. "I see so many people with ADHD who have talent and potential, yet they are unable to achieve their goals because they acquire other problems along with the ADHD, such as substance abuse, that limits their potential. This study is a crucial step toward teasing out the cognitive factors that interfere with their ability to be successful and increase their vulnerability for substance abuse."
"Dr. Fassbender's study is a very important one as the comorbidity of ADHD and methamphetamine dependence has not been studied in great depth," said Ruth Salo, associate professor of psychiatry and behavioral sciences at UC Davis at the UC Davis Imaging Research Center and a study collaborator.
"As there appear to be links between early-childhood attention deficits and exacerbated clinical symptoms among methamphetamine abusers, this study has the potential to increase our understanding of this relationship," Salo said.
The study is funded by a one-year, $150,000 grant from the National Institutes on Drug Abuse of the National Institutes of Health.
Based in Sacramento, Calif., the UC Davis MIND Institute is a collaborative international research center committed to the awareness, understanding, prevention, care and cure of neurodevelopmental disorders. Utilizing the advanced biomedical technology and research infrastructure of UC Davis, the institute's scientists and clinicians pursue investigations that will ensure better futures for the one in twenty Americans with neurodevelopmental disorders. For information, visit www.ucdmc.ucdavis.edu/mindinstitute