6 - Genetic aspects

Summary

Introduction

Beliefs about the nature and etiology of schizophrenia have been influenced by the changing political and social climates of the twentieth century. In the early decades of the century there was a general consensus that schizophrenia was hereditary, but the excesses of the eugenics movement in the 1930s and 1940s, together with the popularity of psychoanalytic theory in North America, and the growth of the antipsychiatry movement in the 1960s resulted in psychiatric genetics becoming decidedly unfashionable (Stromgren, 1994). Despite this, the observation that schizophrenia clusters in families has not been seriously disputed and the past quarter of a century has seen a marked return of interest in the genetic factors involved in schizophrenia. Twin and adoption studies, as described below, provide support for genetic contributions and there is a general consensus nowadays that schizophrenia, although a heterogeneous disorder, has a substantial genetic component to its etiology.

Most genetic research to date concerns adult subjects with schizophrenia, and there is a relative dearth of information regarding the genetics of the childhood onset disorder. This chapter will therefore draw on evidence from adults as well as from the small amount of literature pertaining specifically to children.

Defining the phenotype

Any genetic research requires first that a clearly defined phenotype be agreed upon. With many psychiatric disorders this has not been the case, but it is especially true of childhood onset schizophrenia which has been subject to considerable disagreement regarding its diagnostic boundaries.