Familial aggregation of mood disorders among relatives of schizophrenia probands admitted in a hospital in South-Eastern Nigeria: A family comparative study

Introduction: The debate on the current nosological status of schizophrenia and mood disorders as distinct entities is very active among scholars. There is a paucity of genetic epidemiological data to contribute an African perspective to this debate. Aim: This study aimed to assess the morbid risk of mood disorders in the relatives of schizophrenia probands, in comparison with the families of a sample of healthy controls. Subjects and Methods: This study elicited the information on the morbid risk of mood disorders among 5259 relatives of schizophrenia probands (n = 138) and 6734 relatives of healthy controls (n = 138) through direct interview of patients, available relatives of patients and the comparison group. The family history approach using the Family Interview for Genetic Studies was utilised to obtain information on the morbid risk of all relatives that could be recalled. The diagnosis of available relatives was confirmed using the Diagnostic Interview for Genetic Studies. Morbid risk estimates were calculated using the Weinberg shorter method for age correction. Results: Morbid risk for mood disorders in the first-, second- and third-degree relatives of schizophrenia probands were 1.39% (95% confidence interval [CI] = 1.23-1.55), 0.86% (95% CI = 0.80-0.92) and 0.55% (95% CI = 0.53-0.57), respectively, compared with 0.45% (95% CI = 0.39-0.51), 0.11% (95% CI = 0.07-0.51) and 0.08% (95% CI = 0.06-0.09), respectively, for the healthy comparison group. Conclusion: This result supports the impression that familial risk for mood disorders is significantly higher among relatives of schizophrenia patients, compared with healthy controls and that there could be familial relationship between the predisposition to schizophrenia and mood disorders.