Using new family studies to model the bipolar disorder concept. This model depicts the potential relationships between the three independent dimensions (mania-activation, psychosis and depression) evident in new family studies of common mood disorders and observed clinical syndromes. The shared ‘floor’ of this model is no activation, no depression and no psychotic symptoms. Clinically, Peak A represents the mania-hypomania (high activation, moderate psychosis and low depression) syndrome; Peak B represents the ‘mixed states’ (moderate activation, low psychosis and moderate depression); Peak C represents ‘atypical’ depression (low activation/retardation, low psychosis and moderate depression); Peak D represents psychotic depression (very low activation/retardation, moderate psychosis and high depression). In this model, each clinical syndrome can occur independently. Over the life course, an individual may experience one or more of these specific clinical syndromes but does not necessarily experience both low and high activation states.