Information processing deficits in relatives of manic depressive patients

Background, The importance of genetic factors in the aetiology of manic-dep ressive illness (MDI) has been repeatedly confirmed and indicators of vulne rability to the illness in families with affective disorders are needed. Ab normal event-related potentials (ERP) may be markers of genetic vulnerabili ty to mental illness. Long latency and low amplitude of P300 have consisten tly been reported in schizophrenic patients and their relatives. A few stud ies have also shown P300 deficits in MDI patients, but no ERP study has bee n performed on their relatives. Methods. ERPs were recorded during an auditory oddball task in 19 relatives belonging to families with two or more bipolar patients and in controls wi th no familial or personal history of affective disorders. The relatives we re selected as having no affective disorders on a lifetime basis, but eight had an anxiety disorder. Results. In all relatives, a lower P300 amplitude and a longer P300 latency was found, with much longer reaction time and post-N200 duration till butt on press than controls. A lack of P300 amplitude dominance in the right hem isphere was also found in relatives in comparison with controls. There also appeared to be a frontal predominance of ERP abnormalities in relatives. Conclusion. We report the first evidence of deficits in reaction time and i n P300 amplitude and latency, and a lack of P300 right-sided dominance, in relatives of manic-depressive patients. This pattern may constitute an endo phenotypic marker of manic-depressive disorder.