Structural brain abnormalities in schizophrenia: a family study.
Structural brain abnormalities such as ventricular enlargement are robust correlates of schizophrenia, but the degree of difference compared with unrelated normal controls is only moderate (< 1 standard deviation), and only 40% of patients have values on these measures that fall outside of the normal distribution. Family studies can help to clarify the meaning of this overlap by controlling for some of the non-schizophrenia-related genetic variation in neuroanatomical traits. Computerized tomographic scans of the brain were used to measure ventricular and sulcal cerebrospinal fluid (CSF) to brain ratios (VBR and SBR) for each hemisphere in 16 pairs of discordant siblings from the Copenhagen Schizophrenia High-Risk Project. Schizophrenics' values for VBR and SBR exceeded those of their nonschizophrenic siblings in 75% of the pairs; on average, patients' values on these measures were 1 and 5 standard deviations larger, respectively, than those of their nonschizophrenic siblings. Sulcal and left hemisphere effects were significantly more pronounced than ventricular and right hemisphere effects. After controlling for between-family variation, structural brain abnormalities appear to be more prevalent and more pronounced in schizophrenia than has previously been assumed, with relatively greater deviation observed for cortical and left hemisphere measures of CSF space enlargement.