Biomarker differentiates ADHD subtypes, offers clues for treatment

ADHD is one of the most frequently diagnosed psychiatric illnesses among children, and it's only growing more prevalent. Currently, treatment approaches are more generalized, as subtypes of the disorder have proven tough to distinguish. Now UC Davis researchers think they may have found a biomarker that does just that.

Using a brain-functioning test, the team found differences in the brain waves of adolescents with inattentive and combined subtypes of the condition and those who did not have the condition, suggesting a distinct physiological profile for each. In the past, few markers had been able to detect those differences. "This study shows that there are changes in brain waves related to visual processing and motor planning that can be used to distinguish ADHD subtypes," Ali Mazaheri, a guest researcher at UC Davis from the University of Amsterdam, said in a statement.

Between 2009 and 2013, the researchers studied 57 children between the ages of 12 and 17: 23 ADHD-free participants and 17 in each of two subgroups--inattentive and combined-type. They assessed participants' brain waves while evaluating their performance on a computer test that required them to override their initial impulses in a situation that's particularly challenging for those with ADHD.

The researchers found that those with inattentive ADHD showed different brain-wave patterns from those who struggle with hyperactivity and impulsivity. Alpha-wave patterns of those with the inattentive subtype did not process information offered in the test's visual cues; beta waves, on the other hand, were most distinctly lacking in those with hyperactivity and impulsivity symptoms, suggesting difficulty accomplishing the test's motor task. The team's findings are published in the journal Biological Psychiatry.

The research offers clues for how to develop treatments addressing the underlying processing differences between ADHD subtypes--something most treatments don't take into account, said Catherine Fassbender, a UC Davis researcher, in a statement. As of 2007, parents reported that about 9.5% of children aged 4 to 17--5.4 million in total--have been diagnosed with the disorder, according to CDC data. And with the number of cases on the rise, more specialized approaches could serve a greater need. "Our findings suggest targets for treatment should differ for the ADHD inattentive versus combined subtypes, and that advanced analysis of brain waves may provide a biomarker for testing treatment responses," she said.

- read the release
- and the research abstract

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