This review investigates that up to 50% of patients with affective disorders present with impaired overall functioning, also in remitted phases. Nevertheless, functioning is often overlooked in clinical settings and not incorporated as an essential outcome in research. It is recommended clinically and in research to use the International Classification of Functioning (ICF), e.g. the semi-structured interview Functioning Assessment Short Test (FAST) to ensure a common language and coordination cross-sectionally, interdisciplinarily and across mental and physical diseases.