Study Shows Different Networks Involved in ADHD and Substance Use in Teens
The journey through adolescence is a difficult one for all but the rare blessed teen. For teens with ADHD, there are additional challenges and risks. One of these is a higher rate of experimentation with drugs and alcohol. It has been assumed that the impulsivity of ADHD is intrinsically linked with starting to use drugs and alcohol at an early age. A new study, however, challenges that assumption.
For the study, titled "Adolescent impulsivity phenotypes characterized by distinct brain networks" published in the April 29 issue of Nature Neuroscience, international researchers studied data gathered from testing 1,896 14 year olds in Ireland, England, France and Germany. The study is part of a larger project by a European group called Imagen Consortium.
The main goal of the study was to identify which brain networks are involved in this type of cognitive control in early adolescence. The participants were tested while their brains were being imaged using a functional MRI scanner. The teens' were tested using a standard research protocol called the "stop-signal task" that measures how quickly the participants respond to commands. The subjects were asked to perform a series of manual repetitive tasks with their hands. The "stop" part came in when they were periodically given unpredictable orders to stop moving their hands.
The data was first analyzed to identify the brain networks involved in the activity, and then was sorted into groups according to common characteristics, including those with ADHD, those who had experimented with drugs and alcohol and those that did not fall into either group. The brain networks were then compared for those groups.
The data showed that, in general, teens with ADHD and those who had experimented with drugs and alcohol had a slower reaction time to the stop commands than teens who did not fall into either group. The most interesting finding was that different networks were involved in the impulse control problem for the subjects with ADHD and the drug and alcohol group.
A failure to inhibit behavior (impulsivity) is at least part of the reason for both behaviors: teens with ADHD and teens inclined to start using drugs and alcohol. In theory, when they are faced with the choice of drinking or doing drugs, their faulty impulse inhibition is the reason they say, "yes."
What these results show is that while the impulsivity of these two groups may look the same on the surface, they do not share the same neurobiological cause. Different networks mean different causes of impulsivity, and different causes means that the impulsivity associated with ADHD does not necessarily pre-dispose teens with ADHD to drink and do drugs at an early age - a very heartening thing for any parent of a child with ADHD to hear.
A follow-up study is planned that will look at the brain activity of the participants two years later.