Psychiatric illness stands out as having a rich multifactorial aetiology. This makes it unreasonable to expect massive advances because of the complexity of studies needed to understand it. Acknowledging the multifactorial nature of psychiatric illness, over the past year researchers have tried to consolidate information about different disorders—for example, by studying environmental aspects of the more biological conditions and biological aspects of the traditionally more environmental disorders—and in drawing up treatment protocols. Schizophrenia There have been some promising developments in the treatment of schizophrenia, with both pharmacological and psychological interventions. It is now recognised that the atypical neuroleptic drug clozapine is effective in 30-60% of patients with schizophrenia who do not respond to conventional neuroleptics.1 2 As up to 2% of patients treated with clozapine develop agranulocytosis, obligatory blood monitoring has been introduced, which can be a considerable obstacle to compliance for many chronically psychotic patients. The introduction of clozapine in Britain in 1990 was followed by the release of another atypical neuroleptic, risperidone, in 1993. The clinical effects of these drugs have stimulated investigations into the neurochemistry of schizophrenia and are leading to the formulation and testing of different hypotheses to explain the disorder's complex phenomenology. Conventional neuroleptics are presumed to exert their effect through blockade of dopamine D2 receptors. Clozapine has a more complex pharmacology, with a lower occupancy of D2 receptors and higher occupancy of D1 receptors than conventional neuroleptics,3 4 in addition to potent blockade of 5HT2 receptors. The finding that clozapine also selectively binds to the D4 receptor led to speculation about the role of this receptor in the aetiology of schizophrenia. There is, however, no difference between patients who respond to clozapine and those who do not respond in the distribution of alleles for the D4 gene,5 which suggests that clozapine's …