Sibling pairs with affective disorders: resemblance of demographic and clinical features

• Published in: Psychological medicine Vol. 32; no. 1; pp. 55 - 61
• Main Authors: O'MAHONY, E., CORVIN, A., O’CONNELL, R., COMERFORD, C., LARSEN, B., JONES, I. R., McCANDLESS, F., KIROV, G., CARDNO, A. G., CRADDOCK, N., GILL, M.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.01.2002
• Subjects: Adult and adolescent clinical studies; Age; Biological and medical sciences; Bipolar affective disorder; Bipolar disorder; Bipolar Disorder - diagnosis; Bipolar Disorder - psychology; Bipolar disorders; Demography; Familial factors; Female; Gender; Genes; Genotype & phenotype; Hospitals; Humans; Illnesses; Male; Medical sciences; Mental depression; Middle Aged; Mood disorders; Nuclear Family; Original Article; Psychiatric Status Rating Scales; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Psychosis; Siblings; United Kingdom > UK; Ireland; Mood disorder; Human; Schizoaffective psychosis; Family study; Sex; Depression; Environmental factor; Bipolar disorder; Sibling; Recurrent; Genetic determinism; Psychosis; Symptomatology; Age of onset; Genotype environment interaction; Sociodemographic factor; Evolution; Genetics; Severity score; Diagnosis; Age; Comparative study
• ISSN: 0033-2917; 1469-8978
• DOI: 10.1017/S0033291701004986

Background. As part of a collaborative linkage study, the authors obtained clinical and demographic data on 160 families in which more than one sibling was affected with a bipolar illness. The aim of the study was to identify clinical characteristics that had a high degree of familiality. Method. Data on age at onset, gender, frequency of illness-episodes and proportion of manic to depressive episodes were examined to determine intra-pair correlations in affected sibling pairs. Dimension scales were developed measuring frequency and severity of lifetime mania, depression, psychosis and mood-incongruence of psychotic symptoms; degree of familial aggregation for scores on these dimensions was calculated. Results. Sibling pairs correlated significantly for age at onset (ρ = 0·293, P<0·001); dimension scores for psychosis (ρ = 0·332, P < 0·001); and proportion of manic to depressive episodes (ρ = 0·184, P = 0·002). These findings remained significant when correcting for multiple testing. Of the other test variables; mania (ρ = 0·171, P = 0·019); incongruence dimensions (ρ = 0·242, P = 0·042); frequency of manic episodes (ρ = 0·152, P = 0·033); and frequency of depressive episodes (ρ = 0·155, P = 0·028) were associated with modest correlations but these were not significant after correction. Degree of familial aggregation was not significant for sex (κ = 0·084) or dimension scores for depression (ρ = 0·078, P = 0·300). Conclusions. Significant but modest familial resemblance has been shown for some specific features of bipolar illness, particularly age at onset and degree of psychosis. Further research may establish the extent to which these findings are mediated by genetic and/or environmental factors.