Neuropsychopharmacology: The Interface Between Genes and Psychiatric Nosology

By Thomas A. Ban

5. Alternative Approaches

Discouraged by no limitations of current diagnostic constructs, van Praag (1992, 2000) argues that today's "psychiatric taxonomy" presents diagnostic entities of "dubious validity" and suggests replacing the "nosological disease model" by a "reaction form based disease model" in which "psychiatric conditions" are classified in eight "broad basins": "disturbed reality testing and clear consciousness, " "disturbed reality testing and lowered consciousness," "disturbances in affect regulation," "disturbed cognition," "conditions in which social adaptation and affiliative abilities are disturbed," "conditions with disturbed impulse regulation," "syndromes characterized by termination pathology" and "somatic syndromes without manifest somatic pathology." Others propose to break-up psychiatric disorders into "simpler biological or behavioral components" (Lander 1988; Lander and Schork 1994). And others again, to reconceptualize mental illness, in terms of "discrete neurobiological deficits," i.e, "alternative phenotypes." One of the most intensively studied "alternative phenotype" of schizophrenia is the "abnormality of smooth pursuit eye movement" (Holzman et al. 1988). Another frequently studied "alternative phenotype" is the "P-50-(evoked response) deficit" (Freedman et al. 1999). The former had been linked in genetic studies to a locus on the short arm of chromosome 6 (Arolt et al. 1996) and the latter to the "alpha-7 nicotinic acid receptor" on the long arm of chromosome 15 (Freedman et al. 1997). Nevertheless, the usefulness of these "alternative phenotypes" in genetic research in schizophrenia is questionable, because both "phenotypes" are encountered several times more frequently in the general population than schizophrenia (Faraone, Tsuang and Tsuang 1999).

It has also been proposed to replace "traditional psychiatric nosology" with a "genetic psychiatric nosology" that would classify patients into categories which "correspond with the genes" (Faraone, Tsuang and Tsuang 1999). While such a nosology could focus attention on overlaps between certain traits, e.g., depression and anxiety, it would lump together individuals with genes for a particular disease who fully qualify for the disease with individuals who despite of carrying the genes for the disease are symptom free.

September 14, 2023