Continuity and discontinuity of affective disorders and schizophrenia. Results of a controlled family study.

BACKGROUND: It is widely acknowledged that the genetic diatheses for schizophrenia and affective disorders are independent. However, there are increasing doubts about this classic view, and empirical evidence for a dichotomy of these two prototypes of functional psychoses is limited. A controlled family study of consecutive admissions was conducted to determine whether familial risks for schizophrenic (SCZ) and affective disorders were independent or overlapping. METHODS: Index probands met Research Diagnostic Criteria for SCZ (n = 146), schizoaffective (SA [n = 115]), bipolar (BP [n = 80]), or unipolar major depressive (UP [n = 184]) disorder. Comparison probands met Research Diagnostic Criteria for alcoholism (n = 64) or were sampled from the general population (n = 109). A total of 2845 first-degree relatives were blindly diagnosed from interview, informant, and/or record data, with direct interviews completed in 2070 (82% of living first-degree relatives). RESULTS: By Cox's proportional hazards analysis, SCZ, SA, BP, and UP disorders were familial, in that each group of relatives had an increased lifetime morbid risk (vs those with alcoholism and those from the general population) for the proband's diagnosis. The SCZ and BP disorders were transmitted independently: only probands with manic disorders (BP or SA-BP subtype) showed increased familial risks of BP disorder, and only probands with prominent SCZ features (SCZ or SA) showed increased familial risks of SCZ disorder. However, SCZ probands had an increased familial risk for UP disorder (as did SA, BP, and UP probands) and for the SA-UP subtype. Aggregation of depression in families of SCZ probands could not be explained by the subtype of depression, broad or narrow definition of SCZ disorder, presence or absence of history of depression in SCZ probands, whether onset of depression in a relative occurred before or after onset of a proband's SCZ disorder, or assortative mating. CONCLUSIONS: These data suggest that there could be a familial relationship between the predispositions to schizophrenia and to major depression. We discuss a number of alternative hypotheses about the nature of this possible relationship.

Evidence against linkage of schizophrenia to chromosome 5q11-q13 markers in systematically ascertained families.

Ten pedigrees systematically ascertained in Germany were tested for linkage to chromosome 5q11-q13. In order to replicate the previous report by Sherrington et al (1988), families with a bipolar family member were omitted from the lod score calculations, all diagnoses were based upon Research Diagnostic Criteria, and four different models of the affection status were calculated, including the model for which Sherrington et al calculated the highest lod scores. None of the families investigated showed a positive lod score. Using multipoint linkage analyses, we were able to exclude the region for which a positive linkage has been reported.

Schizoaffective disorder and affective disorders with mood-incongruent psychotic features: keep separate or combine? Evidence from a family study.

OBJECTIVE: This study investigated whether the distinction between schizoaffective disorder and affective disorders with mood-incongruent psychotic features as described in DSM-III-R is reflected by aggregation of schizophrenia in the families of probands with the former disorder and aggregation of affective disorders mainly among the relatives of probands with the latter type of disorders. METHOD: The probands were 118 inpatients with definite lifetime diagnoses of DSM-III-R schizoaffective disorder or a major mood disorder with incongruent psychotic features according to structured clinical interviews. Diagnostic information on 475 of the probands' first-degree relatives was gathered through direct interviews (with 80% of the living first-degree relatives) or the family history approach. The rates of affective and psychotic disorders among these relatives were then compared with those among the relatives of a comparison group of 109 interviewed individuals from the general population who were matched on sociodemographic factors to the inpatient probands. RESULTS: With regard to the familial aggregation of schizophrenia, the DSM-III-R distinction emerged as valid. However, the risk of unipolar affective disorders was enhanced in the families of all of the subgroups of patients studied. The unipolar/bipolar distinction in both DSM-III-R diagnostic groups was reflected by distinct patterns of bipolar disorders in the relatives. CONCLUSIONS: The results partly support the DSM-III-R dichotomy of schizoaffective disorder and affective disorders with mood-incongruent psychotic features. Although the differences between these two diagnostic groups were significant, the magnitude of the differences remained relatively modest.

Systematic screening for mutations in the promoter and the coding region of the 5-HT1A gene.

In the present study we sought to identify genetic variation in the 5-HT1A receptor gene which through alteration of protein function or level of expression might contribute to the genetic predisposition to neuropsychiatric diseases. Genomic DNA samples from 159 unrelated subjects (including 45 schizophrenic, 46 bipolar affective, and 43 patients with Tourette's syndrome, as well as 25 healthy controls) were investigated by single-strand conformation analysis. Overlapping PCR (polymerase chain reaction) fragments covered the whole coding sequence as well as the 5' untranslated region of the 5-HT1A gene. The region upstream to the coding sequence we investigated contains a functional promoter. We found two rare nucleotide sequence variants. Both mutations are located in the coding region of the gene: a coding mutation (A-->G) in nucleotide position 82 which leads to an amino acid exchange (Ile-->Val) in position 28 of the receptor protein and a silent mutation (C-->T) in nucleotide position 549. The occurrence of the Ile-28-Val substitution was studied in an extended sample of patients (n = 352) and controls (n = 210) but was found in similar frequencies in all groups. Thus, this mutation is unlikely to play a significant role in the genetic predisposition to the diseases investigated. In conclusion, our study does not provide evidence that the 5-HT1A gene plays either a major or a minor role in the genetic predisposition to schizophrenia, bipolar affective disorder, or Tourette's syndrome.

Potential linkage for schizophrenia on chromosome 22q12-q13: a replication study.

In an attempt to replicate a potential linkage on chromosome 22q12-q13.1 reported by Pulver et al. [1994: Am J Med Genet 54:36-43], we have analyzed 4 microsatellite markers which span this chromosomal region, including the IL2RB locus, for linkage with schizophrenia in 30 families from Israel and Germany. Linkage analysis by pairwise lod score analysis as well as by multipoint analysis did not provide evidence for a single major gene locus. However, a lod score of Zmax = 0.612 was obtained for a dominant model of inheritance with the marker D22S304 at recombination fraction 0.2 by pairwise analysis. In addition, using a nonparametric method, sib pair analysis, a P value of 0.068 corresponding to a lod score of 0.48 was obtained for this marker. This finding, together with those of Pulver et al. [1994: Am J Med Genet 54:36-43] and Coon et al. [1994: Am J Med Genet 54:72-79], is suggestive of a genetic factor in this region, predisposing for schizophrenia in a subset of families. Further studies using nonparametric methods should be conducted in order to clarify this point.

Personality variations in healthy relatives of schizophrenics.

A familial relationship between schizophrenia and schizotypal personality disorder is widely acknowledged; the familial relationship between schizophrenia and the broad continuum of schizoid personality variation is less clear. In a comprehensive family study healthy relatives of schizophrenics were compared by self rated personality features with relatives of unipolar depressed patients and with relatives of controls. The dimension of schizoidia was not able to distinguish the groups of relatives. However, relatives of schizophrenics (in particular male relatives) scored higher on 'normalized' personality dimensions such as 'rigidity' and 'neuroticism'. Healthy relatives of probands with unipolar depression revealed a similar deviant pattern.

Concordance for gender in sib pairs affected with schizophrenia and related disorders.

An excess concordance by sex among siblings affected with schizophrenia has been proposed by some previous and recent investigators. However, this hypothesis has not been supported by some recent studies having complete ascertainment of probands and relatives. The present report is based on sibships with multiple affected members derived from a family study of systematically recruited inpatients (146 probands with schizophrenia and 132 probands with other psychotic disorders). Evidence for an excess concordance rate for gender among proband-sibling pairs with both members affected is suggested under a broad definition of illness.

Genetic relationship between dopamine transporter gene and schizophrenia: linkage and association.

This study explores the genetic relationship between schizophrenia and the dopamine transporter gene (DAT) by a variety of methods. In a sample of 48 families--each family containing at least one nuclear family with a pair of affected siblings--we performed linkage analysis using the maximum likelihood (LOD score) method as well as sibpair analysis (identity by descent). In addition, we investigated a sample of 108 nuclear families--index case affected with schizophrenia/chronic schizoaffective disorder--for association using the haplotype relative risk method. Linkage between schizophrenia and DAT using two- and three-point linkage analysis was excluded with all disease models employed. No evidence for association between haplotypes of the VNTR-probe of the DAT and schizophrenia has been detected. Thus, a contribution of the DAT gene to the genetic diathesis of schizophrenia is unlikely in the families studied.

Dopamine D3 receptor Gly9/Ser9 polymorphism and schizophrenia: no increased frequency of homozygosity in German familial cases.

Disturbances in the dopaminergic transmission have been implicated in the etiology of schizophrenia. Recently, an association of schizophrenia with increased homozygosity of a Gly9/Ser9 polymorphism in the dopamine D3 receptor gene (DRD3) has been reported (Crocq et al., 1992; Mant et al., 1994). This finding reflected a departure from the Hardy-Weinberg equilibrium in the genotype distribution observed in schizophrenic patients. The effect was found to be at its strongest in patients with a high familial loading. In the present study, we tried to replicate this finding in a sample of 146 German patients with a DSM-III-R diagnosis of schizophrenia. All patients had a positive family history of major psychiatric disorder including 70 patients with a family history of schizophrenia. Given our sample size, we have a power of 99.8% to detect 2. deviation from the Hardy-Weinberg equilibrium of the reported magnitude. However, we found no evidence of an excess of homozygosity in our schizophrenic patients. This seems to indicate that homozygosity for the Gly9/Ser9 polymorphism at the DRD3 locus is unlikely to confer susceptibility to schizophrenia in the German population. This held true whether the psychiatric diagnoses in the affected relatives of the patient samples was established by the family history or family interview method.

Identification of two novel polymorphisms and a rare deletion variant in the human dopamine D4 receptor gene.

We report two novel polymorphisms and a rare deletion variant in the human dopaine D4 receptor gene. The two polymorphisms are characterized by single base pair substitutions, namely a G-->C transversion changing codon 11 from GGG (encoding Gly) to CGG (encoding Arg) and a C-->T transition in position -11 upstream from the start codon. The Arg11 variant occurs at a frequency of about 1% and the C-->T transition at a frequency of about 7% in German control subjects (n = 148). Allele frequencies observed in patients suffering from schizophrenia (n = 256) and bipolar affective disorder (n = 99) were similar. The deletion variant is characterized by a 21 bp deletion affecting codons 36 to 42 coding for amino acids Ala-Ala-Leu-Val-Gly-Gly-Val located in the first transmembrane domain of the dopamine D4 receptor. The mutation was identified in a single individual suffering from obsessive-compulsive disorder and panic disorder. We were unable to detect the deletion in patients with schizophrenia and bipolar affective disorder, nor in healthy controls.

The familial relationship between panic disorder and unipolar depression.

This controlled family study explores (1) whether panic disorder and unipolar depression share familial factors, and (2) whether the co-occurrence of lifetime diagnoses of panic disorder and unipolar depression in individuals defines a distinct diagnostic subtype in terms of familial aggregation. To be most informative, the familial lifetime prevalence rates for panic disorder and unipolar depression have to be determined in a set of four proband groups: 78 patients with unipolar depression and panic disorder. 121 patients with unipolar depression alone (no panic disorder), 81 patients with panic disorder alone (no unipolar depression), and 109 control probands sampled in the general population were compared by lifetime prevalence rates for panic disorder and unipolar depression in their first-degree relatives. Altogether 1046 relatives were interviewed directly; family history information was available on another 346 subjects. Both disorders were aggregating in families. We found modest overlap of familial components; the relative risk of panic disorder only in relatives of patients with unipolar depression only was 2.3, and the relative risk of unipolar depression only in relatives of patients with panic disorder only was 1.8. The comorbid condition did not represent a distinct subtype in terms of familial aggregation. Excess comorbidity was observed in affected relatives independent of the diagnostic status of the index case. Thus, a sharing of familial factors of aetiological relevance between panic disorder and unipolar depression might explain a limited proportion of comorbid cases. However, the major proportion of comorbidity between panic disorder and unipolar depression may still be due to non-familial factors.

The relationship between alcoholism and unipolar depression--a controlled family study.

This family study explores the controversial relationship between unipolar major depression and alcoholism. Thirty-nine families of patients with non-psychotic unipolar depression and alcoholism, 160 families of patients with non-psychotic unipolar depression without alcoholism, and 64 families of patients with alcoholism without psychotic or major affective disorders were compared with 109 families of unscreened probands recruited in the general population. Both disorders were familial. They were transmitted independently in families; a sharing of substantial genetic or of other familial components between the two disorders was unlikely to occur in the sample under study, particularly among male subjects. Comorbidity between the two disorders was more common than expected by chance, but excess comorbidity was preferentially mediated by non-familial factors. Reasons for discrepancies among the conclusions of different family studies on these issues are discussed.

A controlled family study in panic disorder.

There are only a few family studies in panic disorder. Although there is some evidence that panic disorder is familial, the exact figures of the familial risk for this disorder are at variance across different studies; the impact of comorbidity and of the gender of relatives is also unclear. Family studies in panic disorder controlling for the comorbidity in probands are therefore indicated. This study presents the morbid risks in families of 40 "pure" panic disorder probands (DSM-III-R) without a history of psychotic disorders, major depression or alcoholism compared with families of 80 controls recruited in the general population. The relative frequency of panic disorder (DSM-III-R) in the first-degree relatives of panic disorder probands was 5.7% (the age corrected morbid risk is 7.9%) compared to 1.8% in relatives of healthy controls (age corrected morbid risk 2.3%). Agoraphobia segregated predominantly among female relatives of agoraphobic probands. An increased familial risk of major depression and of alcoholism was also observed. Comorbidity with alcoholism and major affective disorders was excluded in panic disorder probands by definition; therefore, these findings indicate that the etiological factors underlying panic disorder may overlap with those of alcoholism and those of unipolar major depression.

Personality disorders among the relatives of schizophrenia patients.

In light of current linkage studies in schizophrenia, research on the "schizophrenia spectrum" deserves increased attention for an exact determination of the affected phenotype: Those disorders that have a much higher prevalence among biological relatives of schizophrenia patients are supposed to share common etiological factors with "core" schizophrenia. However, there is controversy over which of the DSM-III-R personality disorders should be included in the spectrum. In a controlled family study of inpatients with a DSM-III-R diagnosis of schizophrenia (n = 101), schizophreniform and schizoaffective disorders (n = 69), and unipolar major depression (n = 160), familial rates of personality disorders were assessed through personal interviews and compared with prevalence rates in 109 control families from the community. As predicted, schizotypal personality disorder occurred more frequently in the nonpsychotic relatives of schizophrenia probands (2.1%) than in the families of unscreened controls (0.3%). Paranoid personality disorder was more frequent in relatives of probands with unipolar depression (2.9%) than in relatives of schizophrenia patients (1.7%), and controls revealed the lowest rate (0.9%). Schizoid personality disorder, however, was extremely rare in all sample groups (between 0.3% and 0.7%), providing no sufficient statistical power for detection of group differences. Further analysis of the DSM-III-R criterion symptoms of schizotypal personality disorder demonstrated that items describing "negative" symptomatology are the main source of familial aggregation, but "psychotic-like" personality features are also contributing factors.

The familial relation of personality disorders (DSM-II-R) to unipolar major depression.

Four hundred and fifty directly interviewed relatives of probands with non-psychotic unipolar major depression and 320 directly interviewed relatives of controls were compared by the prevalences of personality disorders (P.D.) as defined by DSM-III-R, in relation to presence or absence of the relatives' affective disorder. Overall, there was only a trend for an increased risk for P.D. in relatives of depressed patients. However, P.D. and unipolar major depression co-occurred more frequently in relatives than expected by chance. It is suggested that this association is mainly due to non-familial factors. Compared with other P.D., the relationship of borderline P.D. to major depression was not substantially stronger.

Personality traits in subjects at risk for unipolar major depression: a family study perspective.

Particular patterns of personality (e.g., introversion, neuroticism, obsessionality) have been found to be associated with unipolar depression by a large number of investigators; recent prospective studies have stressed neuroticism as a premorbid risk factor for depression. This study examines whether similar patterns of personality are found in relatives of affective disorder patients and of controls. First-degree relatives of normal controls and of subjects with primary unipolar depression were studied using the Munich Personality Test. Relatives in remission from an episode of unipolar depression had clearly higher levels of neuroticism and rigidity and lower levels of extraversion than controls; healthy relatives of controls had higher levels of rigidity (both sexes) and of neuroticism (males only) than controls. It is proposed that these traits are either risk factors for depression or attenuated forms of depression.

Personality disorders and personality variations in relatives of patients with bipolar affective disorders.

Family studies may elucidate etiological relationships between two psychopathological conditions. This study explored the prevalences of personality disorders (DSM-III-R) and the variation of personality traits measured by the Munich Personality Test (MPT) in first-degree relatives of patients with bipolar disorder in comparison to control families recruited in the general population. Although the overall prevalence of having any personality disorder did not distinguish both groups of relatives we found significantly more compulsive personality disorders among relatives of probands with bipolar disorder. Relatives of patients with bipolar disorder also revealed significantly higher mean scores of "rigidity' (MPT); other personality traits, including neuroticism and extraversion, did not distinguish both groups. The observed differences in personality features between both groups of relatives are not mediated by current or previous axis I disorders. Therefore, they may reflect overlap of etiological factors of familial origin.

Unipolar depression in the aged: determinants of familial aggregation.

Late-onset depression (greater than or equal to 60 years) is believed to be less associated with a risk of depression in first-degree relatives than early-onset depression. However, family studies in elderly probands fitting the current methodological standards of family studies are not available. The reported family study in geriatric inpatients with unipolar major depression (n = 92) supported the proposed relationship between age at onset and the proposed familial loading. A comparison to families of age-matched controls (n = 33) revealed that relatives of probands with late-onset depression are still at an increased risk of depression. However, late-onset depression was not more common in families of probands with late-onset depression than in families of probands with early-onset depression. Besides the age at onset, the recurrence of depressive episodes defined distinct patterns of familial aggregation.

Linkage analysis between pericentrometric markers on chromosome 18 and bipolar disorder: a replication test.

Replication was attempted of a recent report on linkage between bipolar affective disorder and pericentrometric loci on chromosome 18. Linkage to these markers was excluded in a sample of five extended multiplex families using lod-score and affected-pedigree-member methods. In one family, however, the lod score exceeded 1.0. Although the proposed susceptibility genes are unlikely to have a major impact on the occurrence of bipolar disorder, they might modify the genetic risk in a minority of familial cases.

No evidence of linkage between the dopamine D2 receptor gene and schizophrenia.

The antipsychotic effects of dopamine D2 receptor antagonists (neuroleptics) and the psychotomimetic effects of dopamine agonists suggest that a defect of the D2 receptor gene might be a factor in the etiology of schizophrenia. Fifteen families that contained several members suffering from schizophrenia were tested for linkage between the D2 receptor gene and schizophrenia. In addition, four flanking markers were tested. The mode of inheritance was assumed to be dominant. Five different models of the affection status, which ranged from a narrow to a broad definition of the affection status, were studied. Linkage analysis was carried out with dominant, recessive, and intermediate modes of transmission. Two-point and multipoint analyses between schizophrenia and the D2 receptor gene resulted in log-likelihood differences < -2 for all five models, and linkage between this candidate gene and schizophrenia was excluded. A mutation in the D2 receptor gene itself is therefore extremely unlikely to be related to a higher susceptibility to schizophrenia, at least in the present group of families.