Background: Slower and suboptimal decision making has been identified in adults with schizophrenia and bipolar disorder. Owing to the limited evidence on decision making in first-degree relatives, we aimed to investigate, whether alterations in decision making are present in young children at familial high risk of bipolar disorder or schizophrenia.

Methods: In this population-based cohort study we assessed decision making in 197 children at familial high risk of schizophrenia (FHR-SZ), 115 children at familial high risk of bipolar disorder (FHR-BP), and 190 controls aged seven using the Cambridge Gambling Task. Potential associations to neurocognition, psychopathology, and the home environment were investigated.

Results: Children at FHR-SZ or FHR-BP displayed intact decision making. Quality of decision making showed significant but weak cross-sectional associations to neurocognition and adequacy of the home environment. Associations to aspects of executive functions and the home environment differed across groups.

Limitations: Due to the cross-sectional nature of this study, the predictive value of efficient and inefficient decision making remains to be investigated in planned follow-up studies of this cohort.

Conclusions: Young children at FHR-SZ or FHR-BP do not differ from controls in decision making efficacy, which does not appear to be an early risk marker of bipolar disorder or schizophrenia. Decision making is weakly associated to neurocognition and the home environment, but not to general intelligence or psychopathology.