By Eleanor McDermid, Senior medwireNews Reporter
Changes in gray matter volume may be associated with psychosis burden rather than clinical diagnosis, research suggests.
This shows the value of considering psychosis separately from DSM diagnostic category in research “targeting biological markers of serious mental illness,” say study author Elena Ivleva (University of Texas Southwestern Medical Center, Dallas, USA) and co-workers.
The team found that, relative to healthy controls, gray matter volume reductions were largest in patients with psychotic disorders, followed by relatives with lifetime psychotic symptoms (but without axis I disorders), while unaffected relatives had normal volumes.
There were 351 psychosis patients in the study (the Bipolar-Schizophrenia Network on Intermediate Phenotypes [B-SNIP]) – of whom 146 had schizophrenia, 90 had schizoaffective disorder, and 115 had psychotic bipolar I disorder – along with 369 of their relatives and 200 healthy controls. All participants underwent whole-brain structural magnetic resonance imaging.
The observed differences in gray matter volumes “may reflect ‘psychosis burden,’ from extensive reductions in probands where psychosis is fully manifested, to similarly distributed but milder alterations in relatives with mild psychosis spectrum phenotypes, to normal gray matter in relatives without lifetime psychosis spectrum disorders,” say the researchers.
In support of this, gray matter volume reductions in some areas correlated with lifetime psychosis duration and severity of positive symptoms in patients with schizoaffective disorder, and with severity of positive symptoms in those with schizophrenia.
Analyzing patients by diagnostic category yielded similar results. Gray matter reductions were largest among patients with schizophrenia and schizoaffective disorder, affecting mainly the frontal, anterior/posterior cingulate, insular, temporal, parietal, and occipital cortices, and the basal ganglia, thalamus and cerebellum.
Patients with psychotic bipolar I disorder had significant volume reductions relative to controls, affecting the frontal, anterior/posterior cingulate, insular, temporal, and parietal cortices, but their gray matter volumes were significantly larger than those of the schizophrenia and schizoaffective groups.
The team suggests that this “may reflect cumulative lifetime psychosis burden in these psychiatric conditions, with psychosis assumed to be more pervasive in schizophrenia and schizoaffective disorder than in bipolar disorder.”
However, there were no significant differences in gray matter volumes between patients with schizophrenia and those with schizoaffective disorder, which the researchers say “raises questions about the biological uniqueness of the schizoaffective disorder construct.”
On the other hand, the significant differences between these groups and patients with psychotic bipolar I disorder supports this clinical distinction, they add in The American Journal of Psychiatry.
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