Neuropathological studies have largely confirmed the neuroimaging data concerning gross anatomy,77 but there has been much less consistency concerning histopathologica! findings. Three influential papers reported cytoarchitcctonic findings suggestive of altered neuronal migration during fetal life.78-82 Unfortunately, none of these initial reports has been fully replicated.83-87 The other histopathological inhibitors evidence frequently cited in support of a fetal origin of schizophrenia is the absence of gliosis in postmortem schizophrenic brain.88-90
Certainly, the absence of fibrillary gliosis strongly argues against an adult-onset degenerative process; Inhibitors,research,lifescience,medical however, it does not prove a developmental one.91 Thus, we can conclude that there are currently no replicated histopathological findings that unequivocally implicate aberrant neurodevelopmental in fetal life. The causes of structural brain deviances in schizophrenia: nature Inhibitors,research,lifescience,medical or nurture? The environmental factors that we discussed earlier have only a modest risk-increasing effect, and generally operate in the context of genetic risk (Figure 1).92 Inhibitors,research,lifescience,medical The genetic predisposition to schizophrenia has been well established and, recently, two large twin studies have confirmed that a high proportion of the variance in liability to schizophrenia is due to additive genetic effects.93-95 Figure 1. Individual risk factors and their
effect sizes. RR, relative risk. Modified from reference 92: Van Os J, Jones P, Sham P, Bebbington P, Murray RM. Psychosis as a continuum of variation in dimensions of psychopathology. In: Haffner H, Grattaz W, eds. Inhibitors,research,lifescience,medical … A number of investigators have asked whether the firstdegree relatives of people with schizophrenia show any of the same brain structural deviations as their schizophrenic kin. The Maudsley Family
Study96 examined patients and well relatives in families with several schizophrenic members, ie, families assumed to transmit a high genetic load. Sharma et al96 Inhibitors,research,lifescience,medical carried out. MRI scans in patients, well relatives, and controls. They further divided the relatives into standard relatives and presumed “obligate carriers” (relatives who, although well themselves, have psychotic offspring and psychotic siblings or parents and therefore appear to be transmitting genetic risk). The so-called obligate carriers Ergoloid showed a similar increase in lateral ventricular volume to the patients themselves; other relatives were midway between patients and controls, as one might expect from a group in which some, but not all, carry susceptibility genes.97,98 Stefanis et al99 used the Maudsley Family Study samples to show that this is not the whole story. They compared hippocampal volumes in (i) people with familial schizophrenia, but no pregnancy or birth complications (OCs); (ii) people with schizophrenia with no family history but severe OCs; and (iii) controls.