Experts in the field suggest that the locus on chromosome 5 is probably only one of several genetic loci for schizophrenia. Schizophrenia is probably a multifactorial, polygenic disease. In this sense, schizophrenia appears similar to diabetes and hypertension. The manifestation of these diseases requires the accumulation of several genetic defects as well as environmental factors. The fact that drugs are effective in treating schizophrenia supports the idea that this disorder results from biological causes.
Drugs alter brain chemistry.
Some drugs will cause hallucinations. Others will cause delusions. Some will impair social interactions. These drug affect brain chemistry and neuronal function. If experimentally-induced biological changes in brain chemistry cause psychotic manifestations, it would be plausible to hypothesize that genetically and environmentally induced biological changes could also produce psychoses.