The search for neuroimaging and cognitive endophenotypes: A critical systematic review of studies involving unaffected first-degree relatives of individuals with bipolar disorder

The phenomenology and underlying pathophysiology of bipolar disorder (BD) are heterogeneous. The identification of putative endophenotypes for BD can aid in the investigation of unique patho-etiological pathways, which may lead to the development of personalised preventative and therapeutic approaches for this multi-faceted disorder. We included original studies involving unaffected first-degree relatives of BD patients (URs) and a healthy control (HC) comparison group with no first-degree family history of mental disorders, investigating: ‘cold’ and ‘hot’ cognition and functional and structural neuroimaging. Seventy-seven cross-sectional studies met the inclusion criteria. The present review revealed that URs in comparison with HCs showed: (i) widespread deficits in verbal memory, sustained attention, and executive function; (ii) abnormalities in the reactivity to and regulation of emotional information along with aberrant reward processing, and heightened attentional interference by emotional stimuli; and (iii) less consistency in the findings regarding structural and resting state neuroimaging, and electrophysiological measures.