Emotional stimuli response deficits distinguish SMD from bipolar disorder
MedWire News: Adolescents with severe mood dysregulation (SMD) have a blunted response to emotional stimuli that is not seen in adolescents with bipolar disorder, and may therefore help in distinguishing between the two disorders.
Teenagers with SMD are increasingly being diagnosed with bipolar disorder, despite not meeting the DSM-IV criteria for the condition due to lacking manic episodes, note Brendan Rich, from the Catholic University of America in Washington, DC, USA, and colleagues.
“The lack of consensus regarding the diagnostic status of SMD youth has significant clinical ramifications,” they say. “SMD youth diagnosed with bipolar disorder may be prescribed psychotropic medications that are not efficacious, while medications that might treat their depression, anxiety, and attention deficit/hyperactivity disorder may be withheld for fear of causing a manic reaction.”
The researchers explored attention in response to emotional stimuli in 41 patients with SMD (mean age 12.6 years), 57 patients with bipolar disorder (mean age 14.4 years), and 33 mentally healthy individuals (mean age 13.7 years) as a possible means of distinguishing between the two disorders.
They used the Emotional Interruption task, which examined how the presentation of pictures depicting positive, negative, or neutral emotions affects the patient’s ability to perform a basic task of attention.
Based on the patients’ performance, attention interference scores were calculated by subtracting performance on neutral trials from those on emotional trials, taking into account both reaction time and accuracy.
Distracting emotional pictures, compared with neutral pictures, affected the reaction time of patients with bipolar disorder and mentally healthy individuals, whereas the reaction time of SMD patients was unaffected by emotional distracters.
In addition, the team found that positive and negative stimuli affected the performance of SMD patients to a lesser degree than that of bipolar disorder patients and controls, as indicated by significantly lower reaction time attention interference scores. The performances of bipolar disorder patients and controls were similarly affected by positive and negative stimuli.
“In SMD subjects, attention was not modulated by the positive or negative pictures, suggesting a blunted response to emotional stimuli in SMD youth,” Rich and colleagues explain in the Journal of Abnormal Child Psychology.
They also note that SMD patients with the greatest blunted response to emotional stimuli were those with the greatest social dysfunction, based on parent report of social reciprocity deficits and clinician-assessed peer relationship deficits.
The researchers explain that the absence of attention modulation by emotional stimuli may be one cognitive deficit that contributes to the affective and behavioral dysregulation characteristic of SMD.
They hope that their study “represents an initial step toward identifying disease-specific biomarkers eventually capable of complementing clinical data to improve diagnostic accuracy of bipolar disorder in children and adolescents, and clarifying the nosological status of SMD youth.”
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By Lucy Piper