Positive and Negative Symptoms in Psychosis: Description, Research, and Future Directions

By Philip D. Harvey; Elaine E. Walker | Go to book overview

A TWIN STUDY PERSPECTIVE ON POSITIVE AND NEGATIVE SYMPTOMS OF SCHIZOPHRENIA

Howard Berenbaum Ph.D., Thomas F. Oltmanns, Ph.D., and Irving I. Gottesman , Ph.D.

One of the most striking features of schizophrenia is its phenotypic heterogeneity. Schizophrenics differ so markedly among themselves in terms of their presenting clinical symptoms that the usefulness of the concept has been questioned for both clinical practice (e.g., Kanfer & Saslow, 1969) and research purposes (e.g., Bannister, 1968). One suggested alternative, going back to Bleuler ( 1911/ 1950), is to subdivide the schizophrenic population into more homogeneous subgroups. In addition to the traditional subtypes, schizophrenics have been divided into process versus reactive, paranoid versus nonparanoid, and most recently, positive versus negative subtypes. Since it is not yet clear whether these or any other divisions accurately "carve nature at its joints" ( Meehl, 1979), viewing schizophrenia as an open scientific construct ( Meehl, 1972; Neale & Oltmanns, 1980; Pap, 1958) remains a useful approach to the problem.

Perhaps the strongest evidence supporting the validity of the schizophrenia construct is the wealth of evidence indicating that genetic factors play a role in the etiology of the disorder ( Bertelsen, 1985; Gottesman & Shields, 1982). Nevertheless, we do not yet know whether any specific behavioral manifestations of the disorder are genetically influenced. This difficulty has arisen, at least in part, because it is possible for two individuials to be diagnosed as schizophrenics even though they exhibit few, if any, common symptoms. One argument for retaining schizophrenia as a single diagnostic category is based on the hypothesis that all schizophrenics inherit a common underlying factor that predisposes them to develop any of several overt symptoms. Thus, although these individuals may exhibit different symptoms, they all possess the same predisposition in the genotype-to-behavior pathway ( Gottesman & Shields, 1982).

Alternative models of genetic transmission are also possible. For example, predispositions to manifest specific symptoms may be transmitted more or less independently. One individual may inherit

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