Estimating the familial risk of psychiatric illnesses: A review of family history scores.

A history of psychiatric illnesses in family members of those diagnosed to have an illness has been of significant interest both in research and in clinical practice. Almost all of the major psychiatric illnesses have a familial component to them, perhaps influenced by genetics and a shared environment or their combination. Systematic attempts have been made to quantify these familial risks, as obtained from family history (FH) of psychiatric illnesses. The methods range from a simple dichotomous or count scores to those quantifying as weighted risks such as the Family history density (FHD) measures. This article reviews the available literature on such FH methods and discusses their advantages and limitations. Validation studies have shown that FHD measures may be preferred over dichotomous measures as indicators of familial risk. However, the FHD method has certain limitations, like mostly relying on categorical diagnosis and ignoring other familial risk factors. By critically analysing various existing density measures based on 'ideal characteristics', we suggest a modified version of FHD that would benefit psychiatric research.