Neurobiological and behavioural studies of affective instability in clinical populations: A systematic review

•We conducted a systematic review of affective instability in clinical populations.•The review examined neurobiological, psychophysical and behavioural studies.•The review found 29 papers in our criteria, of which 26 were primary studies.•Diagnoses included ADHD, bipolar affective disorder and borderline personality disorder.•The studies converge on the amygdala, and its connectivity in the brain.

ObjectivesTo evaluate the neurobiological, psychophysical and behavioural measures of affective instability in clinical populations.Data sourcesA range of medical and psychological science electronic databases were searched (including MEDLINE, EMBASE, and PsycINFO). Hand searching and reference checking are also included.Review methodsReviews, systematic reviews, experimental and cross-sectional studies, providing affective instability in neurobiological and behavioural measurements in clinical populations. Studies were selected, data were extracted and quality was appraised.ResultsTwenty-nine studies were included, 6 of which were review studies (one a meta-analysis) and 23 of which were primary studies, across a wide variety of disorders including ADHD, bipolar affective disorder, schizophrenia, severe mood dysregulation, major depression, and borderline personality disorder.ConclusionsThe bulk of the studies converge on the role of the amygdala, particularly in borderline personality disorders, and how it connects with other areas of the brain. Future research needs to extend these findings across diagnoses and development.