Abstract
As we approach the end of what in the United States has been termed the decade of the brain, and with a complete map of the human genome in sight, it may be time to try to re-evaluate what the vast increase in molecular knowledge of brain processes has achieved. Certainly there has been no shortage of claims. The abnormal genes and their protein products associated with neurodegenerative diseases such as Huntington's chorea have been identified. Genetic risk factors for Alzheimer's disease are known, and the molecular processes which culminate in the devastating neuronal death and malfunction that are responsible for the disease are subject to intense investigation. However, for neither of these conditions has the new genetic knowledge brought—yet—any effective treatment or prevention. Of course it may come, although not, as many of the advocates of the new genetics once promised, as a result of genetic engineering, but rather because the increased biochemical understanding that follows from genetic information may help in constructing more precisely targeted drugs. Indeed, the best pointer to neuroprotection against Alzheimer's disease has come from epidemiological evidence of the protective effect of hormone replacement therapy in older women rather than from molecular studies. ### Summary points Genes have been identified for several neurodegenerative diseases, but so far this has not led to effective treatment The tendency to view the complexities of human behaviour as genetically determined has important consequences One is the construction of new diseases—for example, disruptive children are diagnosed as having attention deficit hyperactivity disorder and are prescribed methyphenidate hydrochloride Another is that social problems such as violence and alcoholism can be regarded …