McCoy TH, et al. - The link between aggregated genetic liability for depression and medical comorbidity was investigated in this trial, using a novel method for deriving this comorbidity. A complexity was brought to light in the association between mood disorders and comorbid somatic illness. The data indicated specific groups of diagnoses that could traverse along with genetic risk for major depression. The application of a novel approach for aggregating diagnoses was demonstrated, which appeared to be applicable to any large clinical data set, possibly being more tolerant of heterogeneity in diagnostic codes and sensitive to groups of diagnoses that travelled together. The link with mood disorders could be regarded as a replication of the previous report of depression liability genes.