Complicated grief: recent developments in diagnostic criteria and treatment.

Although grief is a natural response to loss among human beings, some people have a severe and prolonged course of grief. In the 1990s, unusual grief persisting with a high level of acute symptoms became known as 'complicated grief (CG)'. Many studies have shown that people who suffer from CG are at risk of long-term mental and physical health impairments and suicidal behaviours; it is considered a pathological state, which requires clinical intervention and treatment. DSM-5 (2013 Diagnostic and statistical manual of mental disorders, 5th edn) proposed 'persistent complex bereavement disorder' as a psychiatric disorder; it is similar to CG in that it is a trauma- and stress-related disorder. In recent years, there has been considerable research on the treatment of CG. Randomized controlled trials have suggested the efficacy of cognitive behavioural therapy including an exposure component that is targeted for CG. However, experts disagree about the terminology and diagnostic criteria for CG. The ICD-11 (International classification of diseases, 11th revision) beta draft proposed prolonged grief disorder as a condition that differs from persistent complex bereavement disorder with respect to terminology and the duration of symptoms. This divergence has arisen from insufficient evidence for a set of core symptoms and the biological basis of CG. Future studies including biological studies are needed to reach consensus about the diagnostic criteria for CG.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'.