[Clinical characteristics of bipolar I patients according to their family history of affective disorders].

BACKGROUND: The familial nature of bipolar disorder has been well described and multiple genes are probably involved in most or all cases. Each gene contributes equally to a bipolar phenotype and it may contribute to clinical characteristics. However, the genetic transmission of bipolar disorder remained undetermined up to now, partly due to clinical and genetically heterogeneity. In Tunisia, genetic study will profit from specific interests and advantages: the high rates of consanguinity, the existence of large families, and the relative geographical stability of the population.

OBJECTIVE: The aim of this study was to compare clinical characteristics of familial and nonfamilial bipolar I disorder.

METHOD: One hundred and thirty subjects met DSM-IV criteria for a bipolar I disorder; they were recruited and divided into groups according to their family history of affective disorders. Group 1 with a familial history group, comporting bipolar I patients with a family history of affective disorders in first and second degree relatives (n = 76; 52 males and 24 females, mean age = 37.2 +/- 10.7 years) was compared to group 2 (nonfamilial history group), comporting bipolar I patients without a family history of affective disorders (n = 54; 29 males and 25 females, mean age = 38.1 +/- 10.9 years). Available information was obtained from a structured clinical interview, collateral history, and medical records. The family investigation permitted completion of genealogies over three generations. The comparison of the two groups was based on the clinical characteristics (age at onset, numbers of affective episodes, nature and severity of the last affective episode,...).

RESULTS: There were no significant differences between the two groups concerning demographic and social features, with the exception of professional activity. Indeed 30.2% of patients with a family history of affective disorders were unemployed versus 12.9% of patients without a family history of affective disorders (p = 0.02). Bipolar I patients with a family history of affective disorders were characterised by an early age at onset of the first episode (before 20 years) (48.7 versus 24.0%; p = 0.004), a high frequency of affective episodes (8.1 +/- 3.6 versus 6.0 +/- 3.5; p = 0.002) and had been more often hospitalised than patients without a family history of affective disorders (5.7 +/- 3.0 versus 4.7 +/- 3.0; p = 0.06). No significant differences were found concerning the nature of the first affective episode in bipolar I patients with or without a family history of affective disorders. Eleven women had developed their first affective episode during the puerperal period; eight of whom had a family history of affective disorders (p = 0.07). The last affective episode was significantly more severe (94.8 versus 77.8%; p = 0.003) and more often associated with psychotic features (55.3 versus 35.2%; p = 0.02) in patients with a family history of affective disorders. After multiple regression, the high frequency of affective episodes and the severity of last episode were more related with a family history of affective disorders.

CONCLUSION: The results of our study provide evidence of familiality for some clinical characteristics which can be useful as phenotypic measures in future molecular genetic studies.