The psychotic hinterlands or the fringes of lunacy

The hinterlands of the major psychoses-schizophrenia and bipolar and unipolar affective disorders-are occupied by both unusual and quite ordinary individuals, only some of whom go on to a full-blown psychosis and some of whom get no worse. This essay deals with the nosological, methodological, and logical issues in trying to identify the relevant disorders or personality dimensions or trait configurations which may be useful to the clinician and to the aetiologist. Multifactorial, polygenic threshold models inform the discussion as do recent developments in the molecular genetic and brain imaging laboratories. So-called schizophrenia spectrum disorders are examined through family, twin, adoption, and prospective high risk strategies. Clinical-phenomenological approaches do not provide sufficient resolving power. Our hope lies with endophenotypes closer to the gene end of the gene-to-behaviour pathways involved in the major psychoses.