Cortical thinning is present in people with nonclinical psychotic symptoms, but is less pronounced than in those with a psychotic disorder, report researchers.
Remko van Lutterveld (University of Massachusetts School of Medicine, Shrewsbury, USA) and colleagues found that, both clinically and in terms of cortical thickness, people with nonclinical auditory verbal hallucinations (AVH) were midway between patients with psychotic disorders and mentally healthy controls.
The 50 nonclinical study participants experienced AVH, which had not arisen from drug or alcohol abuse, at least once a month. They had experienced these for an average of 27.2 years and scored an average of 28.7 points on the Schizotypal Personality Questionnaire, compared with 7.6 among the 50 mentally healthy controls.
Yet these participants with nonclinical AVH had no current or past psychotic diagnoses and had only slightly reduced functioning, scoring 81.0 on the Global Assessment of Functioning (GAF) scale, compared with 87.5 in the control group.
By contrast, the 50 study participants who had psychotic disorders scored 46.7 on the GAF, despite having a shorter average duration of AVH than the nonclinical participants, at 17.6 years.
The neuroimaging findings followed a similar pattern to the clinical findings, report the researchers in Brain.
In a whole-brain analysis, the team identified 11 left hemisphere and 13 right hemisphere regions (out of 34 regions for each hemisphere) in which cortical thickness was significantly less in participants with psychotic disorders than controls. And in five of these areas cortical thickness was also significantly less in the nonclinical AVH participants than controls (left paracentral and pars orbitalis, right fusiform, inferior temporal and insula).
Overall, for 88.2% of the 68 regions examined, the cortical thickness of the nonclinical AVH participants was between that of the controls, who had the thickest measurements, and the participants with psychotic disorder, who had the thinnest.
“These findings provide support from a neuroimaging perspective that psychotic symptoms follow a continuum, such that healthy individuals with normal perceptual experiences are at one end of the continuum, individuals with increasingly strong subclinical psychotic symptoms are in-between, and individuals with a psychotic disorder are situated at the opposite end of the spectrum”, concludes the team.
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