By Liam Davenport
The brain abnormalities observed in patients with schizophrenia are primarily due to processes associated with the disease itself or its treatment, as opposed to being caused by genetic factors, the results of a Dutch study indicate.
As the heritability of schizophrenia is thought to be as high as 81%, it is suggested that schizophrenia-related brain abnormalities may be present in unaffected relatives, a theory that has been supported by evidence from several studies.
To investigate further, Heleen Boos and colleagues from University Medical Center Utrecht performed structural magnetic resonance imaging (MRI) whole-brain scans on 155 schizophrenia patients, 186 of their nonpsychotic siblings, and 122 healthy controls (including 25 sibling pairs).
The images were used for volumetric processing, to determine cortical thickness, and for voxel-based morphometry, with Structural Equation Modeling used to assess group differences. Clinical and neuropsychologic assessments were also performed, the team notes in Schizophrenia Bulletin.
Compared with healthy controls, schizophrenia patients had significant reductions in total brain, gray matter, and white matter volumes, and significant increases in lateral and third ventricle volumes after taking into account age, gender, intracranial volume, and handedness. However, there were no significant differences in brain volume between nonpsychotic siblings and healthy controls.
The researchers also found that schizophrenia patients had cortical thinning compared with healthy controls, and showed decreased gray matter density. Again, no such differences were observed between nonpsychotic siblings and healthy controls.
Of note, Positive And Negative Symptom Scale (PANSS) total symptom scores were inversely associated with total brain and gray matter volumes, while the PANSS total positive symptom score was negatively linked to gray matter volume and positively associated with lateral ventricle volume.
"Our study did not find structural brain abnormalities in nonpsychotic siblings of patients with schizophrenia compared with healthy control subjects, using multiple imaging methods," the team says. "This suggests that the structural brain abnormalities found in patients are most likely related to the illness itself."
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