Trajectories Toward Bipolar Disorder or Schizophrenia in FEP and High-Risk Mental State

Schizophrenia (SCZ) and bipolar disorder (BPD) are two of the most relevant mental disorders, in terms of cognitive and functional impairment, inadequate clinical response and relapsing course. Major efforts have been made to identify diagnosis-specific biomarkers that can help differentiate between SCZ and BPD in the early stage of illness. In this chapter, we aim to better understand what is known in literature about first-episode psychosis (FEP)’s trajectory toward SCZ or BPD diagnosis, in order to establish whether there are indicators in the early stages of disease that could be used to improve targeted therapy and to reduce the significant burden of these serious mental illnesses. In order to do so, we gathered evidences present in modern literature about FEP and we selected four macro-areas of interest to deepen: differences and overlaps in genetics, cognition, neuroimaging, and prodrome/clinical features of FEP patients considering their later diagnoses.