A Critique of the Literature on the Genetics of Schizophrenia.

Abstract

It is essential in any appraisal of our present knowledge of schizophrenia to consider genetic findings carefully, because in the controversy about etiology, they represent one of the main bases for the organic position. Dr. Book has reviewed the topic from the point of view of the medical geneticist; this chapter approaches the question from the psychodynamically oriented side.Much material has been collected by investigators who postulated a major role for genetic factors, and, in their opinion, the data confirm their hypothesis. But one may ask two questions: Are the facts as recorded subject to an alternative explanation? Are the studies sound with regard to method, especially in matters of diagnosis and statistical assumptions?It may be said at the outset that the genetics of schizophrenia is a topic that arouses strong feelings and firm convictions. Although a few individuals, like hl. Bleuler and Kanner, have cautioned against the blanket assumption of a genetic etiology, most writers seem to accept genetic findings, especially as they appear in the work of Kallmann. Recent reviews by Shea (I), Cade (2), and Balfour Ware (3), for example, assume that a genetic basis has been established beyond question. One of the recent reviews of biochemical research (4) quotes Kallmann's statistics and concludes: "Despite the fact that some twin members were reared apart from infancy, the expectation was of the same magnitude. This clearly demonstrates, and such results have been D o n I).

The etiologic role of genetic and environmental factors in criminal behavior as determined from full- and half-sibling pairs: an evaluation of the validity of the twin method

“…Most critics of the twin method suggest that its failures -especially violations of the equal environment assumption -would lead to overestimates of the heritability because the 'extra' environmental similarities for MZ twins would increase the MZ-DZ differences and hence bias the heritability estimates upward (Jackson, 1960;Lewontin et al 1985;Pam et al 1996;Joseph, 2002). This indeed is the specific argument put forward by Burt and Simons in their recent highly critical review of twin studies of crime (Burt & Simons, 2014).…”

“…However, there has been a long history of criticisms of the twin method that have raised questions about its validity (Jackson, 1960;Lewontin et al 1985;Pam et al 1996;Joseph, 2002). These concerns have been highlighted in a recent review in a prominent criminology journal, which argued that twin studies of crime were so flawed that further use of this method should be halted (Burt & Simons, 2014).…”

Peer Reports of Adaptive Behavior in Twins and Singletons: Is Twinship a Risk or an Advantage?

“…Most research has evaluated twin-singleton differences from a negative perspective, anticipating more maladaptive adjustment among twins. At one extreme, twinship, especially MZ twinship, was cast as a psychopathological situation, fostering vulnerability to psychopathology and deficits in cognitive and personality function (Jackson, 1960).…”

Genetic Research in Psychiatry and Psychology

“…Although genetically-oriented authors sometimes mention unnamed ''critics,'' they rarely quote them or take their specific objections seriously. In their discussions of twin method theory and practice, Kendler and Prescott, Faraone et al, and Plomin et al did not even mention that critics exist, even though there have been many such critics (for example, Bleuler, 1978;Boyle, 1990Boyle, , 2002Breggin, 1991;Charney, 2008;Hoffman, 1985Hoffman, , 1991Jackson, 1960;Joseph, 1998Joseph, , 2000Joseph, , 2002Joseph, , 2004Joseph, , 2006Kamin, 1974;Kamin, in Eysenck vs. Kamin, 1981;Laing, 1981;Lewontin, Rose, & Kamin, 1984;Marshall, 1990;Neel & Schull, 1954;Pam, 1995;Pam et al, 1996;Phillips, 1993;Richardson, 1998;Richardson & Norgate, 2005;Rosenthal, 1960Rosenthal, , 1961Rosenthal, , 1962aRosenthal, , 1962b. Only Rutter (2006) referenced a critic who pointed to post-natal environmental influences that might lead MZ twins to resemble each other more than DZs.…”