The Munich Vulnerability Study on Affective Disorders: risk factors for unipolarity versus bipolarity

An individual with a high genetic load for psychiatric disorders is subject to a considerable risk factor for an affective illness. Family studies usually try to distinguish between bipolar and unipolar disorders since it was suggested that they might show different modes of inheritance. The aim of this study was to differentiate between healthy members of unipolar and bipolar families without a previous history of any psychiatric disorder according to the neurobiological and psychometric findings.

We first analysed the results obtained from neurobiological and psychometric measurements taken from 75 healthy subjects who had at least two close relatives with a unipolar and a bipolar disorder. In a second step we examined the subjects with a parental affective disorder; finally, we compared the members of 'pure' unipolar, bipolar and of mixed families to each other.

The first-degree relatives of unipolar patients showed a significantly higher REM density and scored higher on scales of 'neuroticism' and 'vegetative lability' than the controls. No significant differences could be noticed between the relatives of unipolar and bipolar patients, either when considering the degree of relationship, or the parental type of affective disorder and the 'purity' of the respective families.

We found some distinct neurobiological and psychometric differences between the relatives of unipolar patients and the control probands. No obvious differences, however, were ascertained between relatives of unipolar and bipolar patients. Therefore, we consider it to be possible that these findings represent potential vulnerability markers for affective disorders in general.