Social cognition in bipolar I and II disorders: an updated systematic review and meta-analysis

In recent years, there has been a rapid increase in reports upon social-cognition impairments in bipolar disorder. This study aimed to compare the characteristics of social cognition domains in bipolar I (BD I) and II (BD II) based on the findings to date.

A systematic literature search was conducted on Web of Science and PubMed from inception to 28 August 2024. Studies with all-age-group of ICD-10, DSM-IV, DSM-IV-TR, or DSM-5 defined BD (I or II) either in a remitted or symptomatic state were included. The risk of bias was measured using the Newcastle-Ottawa Scale, and the quality of the sources was evaluated using GRADE criteria. Results of the studies were measured by synthesizing Hedge's g effect sizes through a random effects meta-analytic approach.

A total of 20 studies were included, covering three core domains of social cognition (theory of mind (ToM), emotion processing and attributions). There was no significant difference in ToM between BD I and BD II and in emotion processing between non-psychotic patients with BD I and BD II, and history of psychosis negatively predicted performance on emotion processing. Furthermore, BD II performed worse than BD I in attributions, with a low to moderate summary effect size.

BD I and BD II performed similarly on ToM and emotional processing, but BD II had more impaired attributions. Future studies are encouraged to control for the influence of clinical features, to use more neuroscientific techniques, and to explore on other domains of social cognition in bipolar subtypes.