Some studies that were cited by our selected articles but that had not appeared in the search were included as relevant to our criteria. Namely, these were original English-written studies published in peer-reviewed journal that included first-degree relatives of bipolar disorder patients (offspring or siblings/parents), a matched control group, and used fMRI with groups of size 12 and more,except for dizygotic twins. Clinical diagnostic for patients had tobe based on SCID (Structured Clinical Interview for DSM-IV) or K-SADS (Kiddie Schedule for Affective Disorders and Schizophrenia) or other recognized clinical diagnostic criteria (e.g. Diagnostic Interview for Genetic Studies).