Progress towards this goal, however, remains in its infancy, in part because we are only just learning to identify what the genetic liability to schizophrenia looks like before the onset of psychosis. In this paper, we discuss recent progress in this area by focusing on “schizotaxia,” a clinically meaningful condition that may reflect the liability for schizophrenia. We then consider an important implication

of identifying this condition: the possibility of treatment strategies for the primary prevention of schizophrenia. Inhibitors,research,lifescience,medical The development of the notion of schizotaxia, however, begins with a review of how schizophrenia has been classified over the last century, especially in regard to the diagnostic emphasis on symptoms of psychosis, the view of schizophrenia as a discrete category, and the dissociation of clinical symptoms from their Inhibitors,research,lifescience,medical underlying genetic/biological etiologies. Limitations of these approaches are then considered, followed by ways in which genetic research has helped to focus attention on phenotypic expressions of schizophrenia genes (ie, schizotaxia) before Inhibitors,research,lifescience,medical the onset of psychosis. Finally, clinical implications of schizotaxia are considered. The classification of schizophrenia: historical background In 1895, Kraepelin distinguished dementia praecox from manic-depressive

psychoses.1 Dementia praecox referred to patients with global disruptions of perceptual and cognitive processes (dementia), and early onsets (praecox). These patients usually showed an onset in early adulthood, and a progressively deteriorating Inhibitors,research,lifescience,medical course that did not include a return

to premorbid levels of function. In contrast, manic-depressive features included relatively intact thinking, a later onset, and an episodic course in which episodes of psychopath ology alternated with periods of normal function. Eugen Bleuler used Kraepelin’s systematic Inhibitors,research,lifescience,medical classification of psychoses and a theoretical model of etiological processes to reformulate dementia praecox as “schizophrenia,” from the Greek words for “splitting of the mind.”2 His reasoning was that the defects in thinking in schizophrenia were not identical to those occurring in dementias associated with aging, for example, but see more instead reflected deficits of “association.” Bleuler described four basic symptoms: Checkpoint pathway ambivalence, disturbance of association, disturbance of affect, and a preference for fantasy over reality. To Bleuler, these reflected schizophrenia’s fundamental defect: the disassociation or splitting of the normally integrated functions that coordinate thought, affect, and behavior. It is important to note that, in contrast to subsequent Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria, Bleuler’s diagnosis of schizophrenia did not depend on psychotic features such as hallucinations and delusions.