Abstract

This paper performs a critical analysis of Irving Gottesman’s 1991 “Figure 10,” which lists the lifetime risks of developing schizophrenia among the relatives of people diagnosed with schizophrenia. Figure 10, which has been cited in numerous psychiatry and abnormal psychology textbooks, is almost always discussed in support of important genetic influences on schizophrenia. However, the pooled results in Figure 10 can also be explained by environmental factors. Moreover, the risk percentages Gottesman reported are derived from biased research designs, some of which are based on implausible theoretical assumptions, while some results are not included. It is concluded that a closer look at the studies used to compile Figure 10 might lead psychiatrists, psychologists, and genetic researchers to decide that, in addition to problems in schizophrenia adoption research and the ongoing failure to find postulated “schizophrenia genes,” the evidence supporting a genetic basis for schizophrenia is far weaker than is currently believed