Concordance Rates For Schizophrenia Research Articles

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Back to table of contents Previous article Next article LetterFull AccessIn ReplyDaryl E. Fujii, Ph.D., , and Iqbal Ahmed, M.D., Daryl E. FujiiSearch for more papers by this author, Ph.D., Department of Neuropsychology, Hawaii State Hospital, Kaneohe, HI, and Iqbal AhmedSearch for more papers by this author, M.D., Department of Psychiatry, John A. Burns School of Medicine, Honolulu, HIPublished Online:1 Nov 2001AboutSectionsView EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail We would like to thank Dr. Sachdev for his interest in our study. We concur with his argument that traumatic brain injury (TBI) is a significant risk factor for psychosis that deserves further study. Studies of monozygotic twins report that the concordance rate for schizophrenia is roughly 50%.1 This would suggest that environmental factors are also important. Thus far much of the attention in environmental factors has focused on birth complications and illness or maternal stressors during gestation.1 The size effects for these factors, however, are relatively small (between 2 and 3).1 Results from Dr. Sachdev's study as well as ours would suggest that TBI may be another significant risk factor for persons with and without a genetic predisposition for schizophrenia.2,3 Indeed there is evidence that many psychiatric patients have sustained TBI within one year prior to hospitalization.4 Moreover, in many other cases a prior TBI is undocumented in the medical chart.4 We hope that both studies will motivate further investigations into the relationship between traumatic brain injury and psychosis.References1 Jones P, Cannon M: The new epidemiology of schizophrenia. Psychiatr Clin N Am 1998; 21:1-25Crossref, Medline, Google Scholar2 Fujii DE, Ahmed I: Risk factors in psychosis secondary to brain injury. J Neuropsychiatry Clin Neurosci 2001; 13:61-69Link, Google Scholar3 Sachdev P, Smith JS, Cathcart S: Schizophrenia-like psychosis following traumatic brain injury: a chart-based descriptive and case-control study. Psychol Med 2001; 31:231-239Crossref, Medline, Google Scholar4 Burg JS, McGuire LM, Burright RG, et al: Prevalence of traumatic brain injury in an inpatient psychiatric population. J Clin Psychol Med Set 1996; 3:243-251Crossref, Medline, Google Scholar FiguresReferencesCited byDetailsCited ByA Neuropsychological Comparison of Psychotic Disorder Following Traumatic Brain Injury, Traumatic Brain Injury Without Psychotic Disorder, and SchizophreniaDaryl Fujii, Ph.D., Iqbal Ahmed, M.D., and Earl Hishinuma, Ph.D.1 August 2004 | The Journal of Neuropsychiatry and Clinical Neurosciences, Vol. 16, No. 3 Volume 13Issue 4 November 2001Pages 534-534 Metrics History Published online 1 November 2001 Published in print 1 November 2001

Twin Concordance for Schizophrenia Is Not Entirely Hereditary

Monozygotic (MZ) twins have a much higher concordance rate for schizophrenia than dizygotic twins, even when the twins are raised separately. Some

Twin concordance for DSM‐III‐R schizophrenia

The monozygotic (MZ)/dizygotic (DZ) concordance rates for schizophrenia and the relationship between schizophrenia and schizophrenic spectrum disorders were studied in a sample of 31 MZ and 28 DZ schizophrenic probands and their co-twins. All subjects were personally interviewed with structured diagnostic instruments and classified according to DSM-III-R criteria. The concordance rates of 48% for MZ twins and 4% for DZ twins indicate a genetic transmission of DSM-III-R schizophrenia. In addition to the schizophrenic co-twins, 3 MZ co-twins had a noneffective psychotic disorder, thus supporting the hypothesis that genes are involved in the development of Axis I schizophrenic spectrum disorders. Schizotypal and paranoid personality disorders were observed in both MZ and DZ co-twins. These disorders may be familially related to schizophrenia, but a genetic relationship was not confirmed for the Axis II spectrum disorders. A substantial number of MZ co-twins of schizophrenic probands had no mental disorder.

A re-evaluation of the viral hypothesis: is psychosis the result of retroviral integration at a site close to the cerebral dominance gene?

The extent to which concordance rates for schizophrenia in monozygotic twins (between 36 and 58%) fall short of 100% is often taken as an index of the role of an environmental factor in schizophrenia, but such an agent remains elusive. That schizophrenic symptoms are observed in some viral illnesses suggests that schizophrenia might be due to a gene-virus interaction, but analysis of age of onset in pairs of siblings with the disease rules out horizontal transmission. An alternative hypothesis is proposed that onset of disease is due to the expression of a 'provirus', which is integrated in the genome, having been acquired either by prenatal infection or in the germ-line from an affected parent; this could explain why the season of birth effect is accentuated in, and perhaps confined to the group of patients without a family history of the disease. Germ-line integration is known to occur following infection with agents of the retrovirus class. Such agents can integrate at many sites in the host genome, but their interactions with proto-oncogenes (cellular genes which may act as growth factors) identify one type of integration site, and are associated with some of their pathogenic effects. Some characteristics of schizophrenic illness, particularly their selectivity for the dominant hemisphere, can be understood on the assumption that the virus (perhaps a retrovirus) responsible for the disease interacts with a proto-oncogene, which induces the asymmetrical brain growth responsible for laterality and cerebral dominance. The aetiologies of manic-depressive illness and schizophrenia may be related (the season of birth and onset effects are the same for the two conditions) and there is some evidence that the former transmutes into the latter in succeeding generations. The persistence of the functional psychoses may be due to the ability of the psychosis gene (or 'provirus') to induce change in the genetic mechanisms responsible for the development of laterality.

Sex Differences in Schizophrenia: A Commentary*

A critique is offered of Samuels' article suggesting that reported sex differences in concordance rates for schizophrenia are either methodological artifacts or a function of sociological processes. Evidence of sex differences in age of onset, clinical expression, concordance rates among primary relatives, and premorbid competence is cited. Finally, it is concluded that sex differences in schizophrenia offer important clues to the development of the disorder and should be considered in future theories of schizophrenia.

Sex differences in concordance rates for schizophrenia: finding or artifact?

The literature on schizophrenia has reported a trend toward higher concordance rates for females in both monozygotic and dizygotic same-sexed twins. The validity of this finding is open to question. Rosenthal (1961 and 1962) pointed out that females are more likely than males to become inhabitants of chronic wards. Most of the studies reporting a sex difference used resident hospital populations. Gottesman and Shields (1972) noted that the sex difference disappeared when samples were based upon consecutive admissions. Sex differences have vanished in recent studies both as a result of changing research methods and the changing role of women in society.

A comparison of twin and sibling studies for a developmental theory of schizophrenia.

Studies have clearly established that the concordance rate for schizophrenia is much higher in MZ than DZ twins. Beyond this, it is difficult to generalize the findings to singletons. Analyzing the reports of MZ twins discordant for schizophrenia, Stabenau and Pollin (1967) view the differences between the index case and his nonschizophrenic cotwin, as stemming from an early biological defect or immaturity, which, in interaction with parental handling and other environmental response, may lead to socio-psychological incompetency and, in turn, to gross schizophrenic symptomatology.In a previous study (Pollack et al, 1966), comparing schizophrenic patients and their nonschizophrenic sibs, we found that patients showed significant psychological (social and personality) deviations from the preschool age through adolescence. We did not obtain significant differences on the biological and very early developmental variables that clearly distinguished the discordant twins. These include birth weight, paranatal complications or motor development, such as age of walking. In contrast, Lane and Albee (1966) found schizophrenic index cases to be lighter at birth than their sibs, confirming the finding for twins. The clinical significance of this difference is debatable, since the index cases did not differ from national norms.