Shared and specific susceptibility loci for schizophrenia and bipolar disorder: a dense genome scan in Eastern Quebec families.

The goal of this study was to identify susceptibility loci shared by schizophrenia (SZ) and bipolar disorder (BP), or specific to each. To this end, we performed a dense genome scan in a first sample of 21 multigenerational families of Eastern Quebec affected by SZ, BP or both (N=480 family members). This probably constitutes the first genome scan of SZ and BP that used the same ascertainment, statistical and molecular methods for the concurrent study of the two disorders.

A search for specific and common susceptibility loci for schizophrenia and bipolar disorder: a linkage study in 13 target chromosomes.

We report the first stage of a genome scan of schizophrenia (SZ) and bipolar disorder (BP) covering 18 candidate chromosomal areas. In addition to testing susceptibility loci that are specific to each disorder, we tested the hypothesis that some susceptibility loci might be common to both disorders. A total of 480 individuals from 21 multigenerational pedigrees of Eastern Québec were evaluated by means of a consensus best-estimate diagnosis made blind to diagnoses in relatives and were genotyped with 220 microsatellite markers.

Clinical and methodological factors related to reliability of the best-estimate diagnostic procedure.

Objective: The reliability and accuracy of the best-estimate diagnostic procedure were examined, and factors associated with reliability were determined.

Method: The subjects were 134 members of large multigenerational pedigrees densely affected by bipolar disorders or schizophrenia. Three best-estimate diagnoses were derived: first, by a research psychiatrist and research assistant unblind to the relatives' diagnoses; second, by two blind independent psychiatrists; third, by a panel of four blind psychiatrists.

6p24-22 region and major psychoses in the Eastern Quebec population. Le Groupe IREP.

Recent reports of a linkage trend in 6p24-22 for schizophrenia (SZ), in different samples, were tempered by the concurrent evidence of negative reports in other samples. In the studies showing positive results, different definitions of affection and a wide spectrum of diagnoses were used. Our objectives were not only to test for linkage at 6p24-22 in the Eastern Quebec population, but also to test whether this putative vulnerability locus was either selectively linked to schizophrenia (SZ), or to bipolar disorder (BP), or to both major psychoses.

Negative, psychoticism, and disorganized dimensions in patients with familial schizophrenia or bipolar disorder: continuity and discontinuity between the major psychoses.

Objective: This study aimed to answer the following questions: 1) Can we reliably measure the psychopathologic dimensions of schizophrenia by using a lifetime frame and by rating acute and interepisode periods separately? 2) Can we reproduce in subjects with familial schizophrenia the characteristic three-factor structure of schizophrenic symptoms that has been found previously in general groups of schizophrenic patients? 3) Is the factor structure also present in familial bipolar disorder?

Method: Lifetime measures of psychotic symptoms were taken through a slightly modified version of the Comprehensive Assessment of Symptoms and History for 138 patients with highly familial DSM-III-R schizophrenia (N = 51), bipolar disorder (N = 44), or spectrum disorders (N = 43). Symptoms were rated separately in the acute episodes and in the stabilized interepisode intervals across the patients' lives.

Results: A satisfactory level of reliability was obtained.