Differentiating features of BD, early-onset ADHD identified

Research findings published in the Journal of Abnormal Child Psychology have identified differentiating features between early-onset bipolar disorder (BD) and combined attention-deficit/hyperactivity disorder (ADHD-C).

The researchers believe that their findings may help guide understanding of daily life problems and facilitate educational strategies in this patient population, given that differentiation of early-onset BD from ADHD can be difficult. This is due in part to the memory problems present in BD, which are also characteristic of ADHD.

In addition to memory problems, both patient types present affective symptoms, which may further contribute to misdiagnosis of ADHD and BD. "Misdiagnosis is a serious problem because it may lead to unnecessary treatment, with potentially harmful side effects," say Anne Udal (Sörlandet Hospital, Arendal, Norway) and co-authors.

Their comparison of children and adolescents with BD (n=23), ADHD-C (n=26), BD plus ADHD-C (n=15), and 68 healthy controls on memory tests including the Digit span and Children's Verbal Learning Test-II suggests that patients with previous psychotic symptoms and concurrent BD may have inefficient encoding of verbal material. Conversely, memory problems in ADHD-C appear to be characterized by impaired free recall.

The only significant clinical difference observed among the four studied groups was seen for impaired performance on recognition, where the BD plus ADHD-C group did significantly worse than the ADHD-C group.

Notably, only patients with ADHD-C performed significantly below that of controls on working memory, but they showed similar performance during recognition tasks, suggesting that verbal recall problems in ADHD may be due to executive problems rather than a genuine amnestic deficit.

The researchers note that the presence of declarative memory problems similar to that seen in the BD group and working memory problems similar those seen in the ADHD-C group indicates the possibility of some patients exhibiting a "true" comorbid condition.

Subgroup analysis of BD patients according to history of psychotic symptoms showed that individuals without psychotic symptoms performed significantly worse than controls only on the second learning trial. Conversely, patients with previous psychotic symptoms showed significant impairment in delayed recall and recognition compared with patients in the ADHD-C and BD-nonpsychotic groups, indicating a genuine amnestic deficit.

"The recall and recognition problems in the BD-psychotic subgroup indicate a genuine encoding deficit that may be associated with the extremely low level of semantic clustering in this subgroup," comment Udal and team.

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