Strong evidence establishes a close relationship between personality traits and mental illness; where personality can be said to influences the likelihood, severity and longevity of a mental disorder. Personality is usually seen as fixed, yet there is a growing body of evidence for the changeability of personality, though this has rarely been studied in relation to mental disorders.

To study the longitudinal interplay between personality and eating disorders (EDs), particularly the associations between personality, recovery and treatment modality.

To investigate changes in the five domains and thirty lower-level facets of personality in non-underweight EDs, and its associations to intervention and outcome.

Two hundred and nine adults with EDs enrolled either in a four-month multimodal psychodynamic group-therapy (DAY) or four-six month internet-based supported cognitive behavioural therapy (iCBT). ED diagnosis and personality (by the five-factor model) were assessed at baseline, termination and 6-month follow up. Structural equation modeling was used to analyze domain-level development, and reliable change (RCI) for facet-level development.

Remission rate at end of treatment was 71% in DAY and 55% in iCBT. Over time, Neuroticism decreased significantly while Extraversion, Openness and Conscientiousness increased (P < 0.01). Treatment and outcome had little influence on domain-level change. At the facet-level, 28% of patients reliably changed in any given facet, and there were several differences in pattern based on treatment and outcome.

This study lends support for the possibility of personality change and its relevance for recovery from EDs.

The authors have not supplied their declaration of competing interest.