An Individual Meta-Analysis of Psychological Treatments for Mood and Personality Disorders Using the Severity Diagnostic System of ICD-11

An individual patient meta-analysis was carried out to investigate the impact of the four levels of severity of ICD-11 personality disorder on the short-term outcome (12-24 m) of anxiety and depressive symptoms and social function in 1384 patients included in four randomised trials in which psychological treatments, mainly linked to cognitive-behaviour therapy, were compared with standard controls. In each of these trials, a proxy form of the ICD-11 classification system was used to assess personality status. The results showed that in those with more severe personality pathology, mood symptomatology was greater and showed a consistent linear trend with normal personality showing the least pathology and severe personality the most. Improvement in anxiety symptoms was significantly less in those with moderate and severe personality disorder compared with those with no personality disorder. Depressive symptoms did not show the same changes except in one trial. Social function improved in all patients in the studies. Treatment effects were small and not significantly different. The findings give some support to the dimensional system of classifying personality disorder and confirmed that all levels of personality dysfunction, including the sub-syndromal condition of personality difficulty, have an impact on mental health symptomatology and function. Suggestions for improving the utility of the classification are made. In particular, the domain structure appears to have a major influence on clinical outcomes.