Behavioral testing of adolescents identified 3 distinct subgroups, suggesting there is not a clear-cut explanation for the disorder.
Yale researchers recently conducted a study that found patients with different types of attention deficit/hyperactivity disorder (ADHD) have impairments that represent unique brain systems. This could indicate there may not be a clear-cut explanation for the cause of the disorder.
Unlike a single disorder that contains small variations, the findings of this study suggest that the diagnosis instead encompasses a “constellation” of different types of ADHD during which the brain functions in drastically different ways, researchers reported in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
This study was based on behavioral tests for 117 adolescents with ADHD to assess different types of impulsive behavior, which is a typical feature of ADHD. Based on the results, adolescents with ADHD fit into 3 subgroups. Each subgroup established distinct impairments in the brain with no common abnormalities between them. One group displayed an inclination towards immediate reward, another showed impulsive motor responses during fast-moving visual tasks, and the third group showed normal performance on both tasks when compared with 134 non-ADHD adolescents.
“This study found evidence that clearly supports the idea that ADHD-diagnosed adolescents are not all the same neurobiologically,” said one of the authors of the study, Michael Stevens, PhD.
After the tests were conducted, Yale researchers then used functional magnetic resonance imaging (fMRI), which allows administrators to make connections between behavior and brain function.
“Far from having a core ADHD profile of brain dysfunction, there was not a single fMRI-measured abnormality that could be found in all 3 subgroups,” said Stevens. Rather, the tests showed dysfunction in brain regions related to the specific type of behavioral impairment displayed.
“Ultimately, by being open to the idea that psychiatric disorders like ADHD might be caused by more than one factor, it might be possible to advance our understanding of cause and treatments more rapidly,” he said.