Background. Electrophysiological endophenotypes are far less explored in bipolar disorder as compared to schizophrenia. No previous twin study of event-related potentials (ERPs) in bipolar illness has been reported. This study uses a twin design and advanced genetic model fitting analyses aiming to (1) assess and quantify the relationship of a range of ERP components with bipolar disorder with psychotic features, and (2) examine the source of the relationship (due to genetic or environmental factors).
Method. P300, P50 suppression and mismatch negativity (MMN) were recorded in 10 discordant monozygotic (MZ) bipolar twin pairs, six concordant MZ bipolar twin pairs and 78 control twin pairs. Statistical analyses were based on structural equation modelling.
Results. Bipolar disorder was significantly associated with smaller P300 amplitude and decreased P50 suppression. Genetic correlations were the main source of the associations, estimated to be −0·33 for P300 amplitude and 0·46 for P50 ratio. Individual-specific environmental influences were not significant. MMN and P300 latency were not associated with the illness.
Conclusions. The results provide supporting evidence that P300 amplitude and P50 suppression ratio are ERP endophenotypes for bipolar disorder.