The relationship between social cognition and social behaviour in patients with neurodegenerative diseases: a systematic review

Objectives. Changes in behaviour are often reported in neurodegenerative diseases, such as frontotemporal dementia (FTD), Alzheimer’s disease (AD), Parkinson’s disease (PD) and Huntington’s disease (HD). Changes in social and emotional behaviour include disinhibition, apathy, irritability, compulsive behaviour, aggression, risk-taking and agitation. Although the management of behavioural changes is extensively covered in the research literature, relatively little is known about the impairments that may underlie and predict social behavioural changes. It is often assumed that impairments in social cognition (SC) underlie these behavioural changes. If someone is not able to correctly perceive someone’s emotions or unable to experience emotions themselves, this might lead to inappropriate behaviour. Although associations between some aspects of SC and social behaviour have been studied, the current study will be the first to systematically study associations between SC and social behaviour in patients with neurodegenerative diseases and provide a full overview.

Methods. In line with the PRISMA guidelines, a systematic search was conducted in the Pubmed and PsychINFO databases at September 5th 2023. Main criteria for selection were that the participants were adult persons with a neurodegenerative disease, social cognition was assessed with a performance-based measure, social behaviour was assessed through a proxy report, and correlations between social cognition and social behaviour were reported. Quality of the included studies was assessed with the mixed methods appraisal tool.

Results. Of the 1538 publications identified in the search, 27 were selected by two independent reviewers. In 19 of the 27 studies a measure of emotion recognition was used and 11 of the 27 studies included a measure of Theory of Mind (ToM). 4 studies included a composite measure of SC including emotion recognition tasks and ToM tasks. Measurement of social behaviour was more diverse with different scales being used and different behavioural aspects being measured. The social behaviour measure was most often a measure of total behaviour, apathy or disinhibition. With regard to the association between SC and social behaviour, the results were mixed with approximately half of the studies finding an association between some measure of SC and some measure of social behaviour, but the other half did not.

Conclusions. The results points towards the existence of a relationship between social cognition and social behavioural problems, as in approximately half of the studies such an association is found. However, in the other half of the studies no association was found and variability between the publications is high, with different patient groups being included and different aspects of social cognition and social behaviour being measured with different instruments. The limited amount of comparable studies would also make it difficult to perform a meta-analysis on the results. For future research it is imperative to create more unity in the instruments used to measure social cognition and social behaviour, and to add to the literature on this association to get a better more comprehensive understanding of effects of SC impairments on social behaviour. Consequently the better understanding could give rise to the development of appropriate interventions for social behavioural problems.