Schizoaffective disorder the ‘most severe’ psychosis
medwireNews: Schizoaffective disorder may be the most serious of the psychotic disorders in terms of patients' long-term cognitive outcomes, research suggests.
Researchers led by Pamela DeRosse (The Feinstein Institute for Medical Research, New York, USA) used cross-sectional data drawn from the clinical records of 993 patients with psychotic diagnoses to analyze the course of their illnesses.
They found clear differences between the 371 patients with schizophrenia, the 224 with schizophrenia plus a mood syndrome, the 129 with schizoaffective disorder, and the 269 with bipolar I disorder with psychotic features. This suggests that "the identification of differences in longitudinal clinical and neurocognitive profiles in patients suffering from a range of psychotic illnesses is possible," note the researchers in PLoS One.
This may be particularly pertinent in the case of schizoaffective disorder, which they say "has often been referred to as a 'diagnosis by exclusion.' "
Their most striking finding is that cognitive decline was greatest in patients with schizoaffective disorder. The reduction from premorbid IQ, estimated from the Wide Range Achievement Test-Third Edition-Reading Subtest, to current IQ, gauged from a battery of neurocognitive tests, was largest in the schizoaffective disorder group and significantly more than that in patients who had bipolar disorder with psychotic symptoms. The other two groups had intermediate reductions.
The between-group differences in cognitive decline persisted after accounting for factors including age, gender, illness duration, general functioning, and symptom severity.
This suggests that schizoaffective disorder may be the most severe form of psychotic illness, contrary to previous beliefs, say DeRosse et al.
"Moreover, these results do not appear to be driven by a single cognitive domain as the patterns of raw scores across diagnostic groups are consistent across most domains," they comment.
Lifetime severity of symptoms was not notably worse among schizoaffective disorder patients than the other groups, however. Severity of psychosis was worse than that of the bipolar group, but similar to that of the other schizophrenia groups, while affective symptoms were more severe than in the other schizophrenia groups but milder than those of the bipolar group.
Again, there were significant differences among the four groups. Psychosis was significantly milder in the bipolar group than the schizophrenia groups, among which there were no significant differences, while affective symptoms were significantly different between all four groups, with a gradient of increasing severity from pure schizophrenia to bipolar disorder with psychotic features. The latter finding was driven largely by between-group differences in mania severity.
The team concludes that schizoaffective disorder "may represent a disease entity that is distinct" from both schizophrenia and bipolar disorder.
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By Eleanor McDermid, Senior medwireNews Reporter