Delayed WM growth in siblings of childhood-onset schizophrenia patients

By Mark Cowen, senior medwireNews Reporter

The unaffected adolescent siblings of patients with childhood-onset schizophrenia (COS) show reduced white matter (WM) growth rates compared with other adolescents, researchers report.

However, Paul Thompson (University of California at Los Angeles School of Medicine, USA) and colleagues note that WM growth rate deficits were only evident in siblings of patients with COS until the age of 14 years, after which growth rates normalized.

"This normalization effect has… been reported for the gray matter deficits in these siblings," say the researchers, who add that "WM growth may also be an age-specific endophenotype that shows compensatory normalization with age."

The team studied 49 mentally healthy siblings of patients with COS and 57 age- and gender-matched mentally healthy controls without a family history of psychiatric illness in first-degree relatives.

Using anatomic magnetic resonance imaging, WM growth rates over 5 years were assessed in three age groups: preadolescents (7 to <14 years), postpubertal adolescents (14 to <18 years), and young adults (18 to 28 years).

The researchers found that in the preadolescent group, the siblings of COS patients showed significantly reduced WM growth rates in the parietal lobes compared with controls.

Post hoc analysis revealed that this difference in WM growth rates was limited to the left parietal lobe.

Interestingly, 3D mapping appeared to show a greater increase in WM growth rates in the siblings compared with controls in the latter age groups, but the difference was not significant.

"Our study provides the first evidence of WM growth alterations in nonpsychotic siblings of patients with COS as a time-limited trait marker," conclude the researchers in the Archives of Psychiatry.

They add: "Ongoing studies with alternative imaging modalities will investigate the agreement across measures of brain maturation and examine connectivity patterns across development."

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