Mixed state specifier in DSM-5 overlooks the core features

Feb 19 2014

By Lucy Piper, Senior medwireNews Reporter

The replacement of “mixed episodes” with “mixed features” in DSM-5 in order to counter a lack of specificity overlooks two of the core features of mixed states, suggests research published in the Journal of Affective Disorders.

Psychomotor agitation and distractibility are excluded in the latest DSM definition, but in an analysis of 114 patients with unipolar depression, these two symptoms were among the most commonly endorsed items on the Mood Disorder Questionnaire (MDQ).

“[T]heir exclusion when diagnosing mixed features (DSM-5) will fundamentally alter the trajectory of research and the implications of future findings,” say lead researcher Gin Malhi (Royal North Shore Hospital, Sydney, New South Wales, Australia) and colleagues.

“Excluding these features from the diagnostic criteria for mixed features is akin to a statistician sampling a population but then excluding those who fall within the middle of the distribution; i.e., the archetypes of the population.”

A total of 200 patients participated in the study. Following clinical evaluation by a psychiatrist, 114 were diagnosed with unipolar depression and 86 with bipolar disorder (51 with bipolar I disorder and 35 with bipolar spectrum disorder).

Fifty patients from the unipolar depression group completed the MDQ. The most commonly endorsed items were increased distraction (65%), racing thoughts (65%) and increased irritability (63%).

Based on MDQ scores, there was a clear binomial distribution between patients who endorsed at least six items and were considered to have unipolar depression with mixed features and those who endorsed five items or fewer and who were classified as having depressive symptoms.

The researchers note that the four groups – unipolar depression, unipolar depression with mixed features, bipolar I disorder and bipolar spectrum disorder – did not differ with regard to age, education, or anxiety and depression scores.

But the groups did differ significantly with regard to psychomotor agitation on the MDQ. Patients with unipolar depression with mixed features had significantly more psychomotor agitation than those with depression without mixed features and patients with bipolar I disorder. And the latter group had less psychomotor agitation than patients with bipolar spectrum disorder.

Also, more patients with depression with mixed features and bipolar spectrum disorder experienced distractibility than those with depression without mixed features and bipolar I disorder, at 71% and 67% versus 54% and 40%, respectively.

“Despite a relatively modest sample size, this study does indicate that mixed states have a signature that is most likely penned with a significant contribution from psychomotor agitation and distractibility, and that DSM-5 may have missed the mark,” the researchers conclude.

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