Kærsgaard S, et al. - Researchers investigated affective cognition in monozygotic twins at familial risk of bipolar disorder relative to those at risk of unipolar disorder and to low-risk twins. In this work, increased recognition of low to moderate intensity of happy facial expressions was noted among twins at familial risk of bipolar disorder relative to both unipolar disorder high-risk twins and low-risk twins. Hence suggesting that increased sensitivity and reactivity to positive social stimuli could be a neurocognitive endophenotype that is specific for bipolar disorder. This ‘positive endophenotype’ could aid diagnostic differentiation between unipolar and bipolar disorder in future.