fMRI Distinguishes Between Bipolar Disorder and ADHD

Deborah Brauser

June 16, 2011

June 16, 2011 (Pittsburgh, Pennsylvania) — Areas of working memory activation differ between pediatric bipolar disorder (BD) and attention-deficit/hyperactivity disorder (ADHD), according to new research.

A small functional magnetic resonance imaging (fMRI) study showed that youths with BD used more of the limbic brain network and those with ADHD used more of their fronto-subcortical network during working memory tasks.

"This study is among the first to directly compare neural biomarkers in these patient populations [and] the results provide preliminary evidence of differing neural networks that are active," lead author Patricia D. Walshaw, PhD, from the Department of Psychiatry and Biobehavioral Sciences at the University of California, Los Angeles, told delegates here at the 9th International Conference on Bipolar Disorder.

According to the study authors, distinguishing between the 2 disorders in children has been difficult in the past because of a "significant overlap in symptoms."

They note that the goal of this study was to assess biosignatures that would help to "supplement current clinical judgment."

Twelve participants between the ages of 7 and 17 years (mean age, 11.77 years; 72% female) diagnosed with BD and 12 age-matched participants with ADHD were enrolled. All participants performed a spatial working memory task while undergoing fMRI.

"Signal response was then analyzed for each stage of working memory (encoding, maintenance, and retrieval) using whole-brain mixed-effects analysis," report the researchers.

Results showed that the BD group had greater activation than the ADHD group only during the maintenance phase of working memory (in the right and left paraphippocampal gyrus and the left medial geniculate nucleus; P = .05).

The ADHD group showed greater activation than the BD group only during the retrieval phase of working memory (in the ventromedial prefrontal cortex, ventral anterior cingulate, and left caudate nucleus; P = .05).

These results "may indicate that individuals with these disorders may be processing spatial material differently despite having similar behavioral accuracy on the task," the investigators note.

'Exactly What We Need'

"I think it's very helpful to begin to look at the neural correlates of this kind of working memory task because discriminating between pediatric bipolar and ADHD is a key issue," Robert M. Post, MD, director of the Bipolar Collaborative Network in Bethesda, Maryland, told Medscape Medical News.

"It would be very interesting to see if they can turn this thing around and use it as a predictor. Whether the findings are robust enough to do that, I'm not sure. But it would be extremely helpful because you treat ADHD and bipolar so oppositely."

"The idea of doing these correlates is crucial. And if you could even see if this happens before these illnesses start in people at high risk, that would be truly wonderful," he added.

Dr. Post, who was previously chief of the Biological Psychiatry Branch at the National Institute of Mental Health, noted that studies like this "are exactly what we need" so that adolescents can begin receiving treatment earlier.

"We've found that the duration of the delay to first treatment is directly proportionate to how lousy adults do at average age of 40 with bipolar. So if we can shorten that delay, maybe we can make the illness much more benign," he concluded.

The study was funded by a grant from the National Institute of Mental Health. The study authors and Dr. Post have disclosed no relevant financial relationships.

9th International Conference on Bipolar Disorder (ICBD): Poster P233. Presented June 10, 2011.

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