Brain structure linked to psychosis symptoms

By Eleanor McDermid, Senior medwireNews Reporter

A study of patients across the psychosis spectrum supports an association between brain structure and psychosis symptoms.

In line with previous studies, cortical thickness had a larger effect than cortical surface area, and brain structure was more strongly associated with positive than negative symptoms.

“Notably, although correlations were significant, their magnitudes were small, indicating that other factors likely make independent contributions to symptom severity”, say study author Matcheri Keshavan (Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA) and co-workers.

The study included 455 patients with psychosis who underwent structural magnetic resonance imaging as part of the Bipolar-Schizophrenia Network for Intermediate Phenotypes study.

Overall, reductions in right temporal cortical thickness, as well as bilateral frontal and right temporal grey matter volume (GMV), correlated with more positive symptoms on the Positive and Negative Syndrome Scale (PANSS), while right frontal cortical surface area reductions correlated with increased negative PANSS scores. In addition, lower total GMV was associated with higher total and positive PANSS scores.

A total of 58 out of 212 screened brain regions correlated to some degree with the positive PANSS subscale. Factor analysis to detect brain areas with enriched correlations identified four factors: a temporal cortical thickness factor, a frontal GMV factor, a frontoparietal cortical thickness factor and a precuneus GMV–cortical surface area factor. These factors contained between four and 13 regions that correlated with positive PANSS scores.

Fourteen brain regions correlated with negative PANSS scores, and the team identified just one factor, a frontal GMV–cortical surface area factor, which contained 10 of these regions.

“Overall, the negative subscale demonstrated fewer correlations with structural measures than the positive subscale”, comment the researchers in Schizophrenia Bulletin. “This observation may indicate the relatively greater contribution of social and nonstructural biological influences in the manifestation of negative symptoms.”

Of the patients in the study, 181 had a diagnosis of schizophrenia. These patients had stronger correlations between brain structure and PANSS scores than the 117 patients with schizoaffective disorder or the 157 who had bipolar I disorder with psychotic features.

However, in the factor analysis, diagnosis had no significant effect on the relationships between the structural factors and PANSS subscales.

“Overall, findings in the schizophrenia group may reflect their higher level of subtle brain pathology, which may in turn be associated with their more chronic and persistent psychotic symptoms compared with schizoaffective and bipolar I disorders”, the team suggests.

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