By Mark Cowen, Senior medwireNews Reporter
Bipolar disorder (BD) patients with and without comorbid attention-deficit hyperactivity disorder (ADHD) differ in neural activation patterns during response inhibition, results from a US study show.
The team found that BD patients with ADHD (BD+ADHD) had significantly greater activation in a number of brain regions than those with BD alone.
The findings, published in the Journal of Affective Disorders, suggest that in neuroimaging studies, "grouping the BD [alone] and BD+ADHD participants together may lead to incorrect conclusions about the pathophysiology of BD," say Lori Altshuler (David Geffen School of Medicine at the University of California Los Angeles) and colleagues.
The researchers studied 16 patients with BD alone, 16 with BD+ADHD, 16 with ADHD alone, and 30 mentally healthy controls.
All four groups were similar in term of mean age and gender distribution. In addition, there were no significant differences between the BD alone and BD+ADHD groups regarding mood symptom severity, and no significant difference between the ADHD alone and BD+ADHD groups regarding ADHD symptom severity.
All of the participants underwent functional magnetic resonance imaging of the brain while performing a response inhibition task (the Go/No-Go task).
Analysis of the findings revealed that patients in the BD+ADHD group had significantly greater activation in the anterior cingulate (Brodmann area [BA] 24/32), the posterior cingulate, and bilateral thalamus than those with BD alone.
BD+ADHD participants also showed significantly greater activation than those with BD alone in the left inferior frontal cortex (BA 44), the right superior frontal gyrus (BA 10), the right parahippocampal, and left supramarginal gyrus. There were no significant areas of increased activation in BD alone patients versus BD+ADHD patients.
The team also found that BD+ADHD patients had significantly greater activation than controls in the bilateral anterior cingulate (BA 24/32), posterior cingulate, right thalamus, bilateral medial frontal gyrus (BA 9) and left parahippocampal gyrus. There were no areas where controls had significantly greater activation than BD+ADHD patients.
Altshuler et al conclude: "Future studies that examine not only neural differences in specific brain regions, but also assess how these regions may interact (connectivity studies) may provide further insight into the differences in neural patterns in BD, BD+ADHD, and ADHD."
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