Family history identifies sporadic schizoaffective disorder as a subtype for genetic studies.

Nicolaas J Van Der Merwe,René Ehlers,Johannes L Roos,Maria Karayiorgou

doi:10.4102/sajpsychiatry.v26i0.1393

Abstract

BackgroundSchizophrenia is a heterogeneous disorder with strong genetic vulnerability. Family history of schizophrenia has been considered in genetic studies under several models. De novo genetic events seem to play a larger role in sporadic cases.AimThis study used the familial–sporadic distinction with the aim of identifying a more homogeneous phenotype to delineate the genetic and clinical complexity of schizophrenia.SettingThe study was conducted at Weskoppies Hospital, Pretoria, South Africa.MethodsThe study included 384 participants with schizophrenia or schizoaffective disorder from the Afrikaner founder population in South Africa who are considered comparable to Caucasian patients from the United States. A comprehensive data capturing sheet was completed.ResultsWhen schizophrenia and schizoaffective disorder diagnoses were considered jointly, we found no significant differences between the sporadic and the familial groups for age at disease onset, season of birth, comorbid diagnoses, clinical symptomatology, history of suicide or marital status. When the diagnoses were examined separately, however, the sporadic schizoaffective disorder, bipolar type, was found to have a significantly lower age at onset (mean 20.6 vs. 25.3 years).ConclusionThe sporadic schizoaffective disorder, bipolar type, forms a more homogeneous subgroup for genetic studies.

Highlights

Schizophrenia is considered etiologically as a heterogeneous group of disorders.[1]
Any subject with a first-degree, second-degree or third-degree relative diagnosed with schizophrenia or schizoaffective disorder was considered as a familial case for the analyses presented here
In the combined schizophrenia and schizoaffective group, when controlling for diagnosis, the odds of being a male subject and single was four times higher compared to female participants (95% confidence interval [CI] = 2.5, 6.3; p < 0.0001), an association driven mostly by the schizoaffective disorder bipolar type group, where the corresponding odds ratio was 4.6

Summary

Introduction

Schizophrenia is considered etiologically as a heterogeneous group of disorders.[1]. Against this background of considerable heterogeneity, the presence of mental illness in close relatives (familial cases) versus no history of mental illness in close relatives (sporadic cases) has been considered in genetic studies.[2,3,4] This criterion represents one of the multiple strategies used to define a more homogeneous group of subjects.[5]It is difficult to ascertain familiality accurately, especially in outbred populations where families are largely mobile and historical data on multiple family members are scarce. Schizophrenia is considered etiologically as a heterogeneous group of disorders.[1] Against this background of considerable heterogeneity, the presence of mental illness in close relatives (familial cases) versus no history of mental illness in close relatives (sporadic cases) has been considered in genetic studies.[2,3,4] This criterion represents one of the multiple strategies used to define a more homogeneous group of subjects.[5]. Significantly increased rates of de novo copy number variants have been reported in sporadic, as opposed to familial cases of schizophrenia,[1,4] and de novo singlenucleotide polymorphisms are more common.[1] This provides evidence for an association on a genetic level, with at least some mutations enriched in sporadic cases.[1]. Schizophrenia is a heterogeneous disorder with strong genetic vulnerability. History of schizophrenia has been considered in genetic studies under several models. De novo genetic events seem to play a larger role in sporadic cases

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