Why is an evidence-based classification of personality disorder so elusive?

Despite recent revisions, the classification of personality disorder remains a matter of dispute, and there is little evidence of consistent progress toward an evidence-based system. This essay examines four issues impeding taxonomic progress and explores how they might be addressed. First, the phenomenological and aetiological complexity of personality disorder poses a formidable challenge to traditional taxonomic methods. Second, current classifications incorporate assumptions such as a stringent version of medical model and an essentialist philosophy that are inconsistent with empirical evidence. Third, despite the claims of trait psychology, a viable alternative to categorical diagnosis is not available. Contemporary trait models have not gained widespread clinical acceptance and substantial conceptual and methodological limitations compromise their clinical value. Finally, the processes used to revise official classifications are biased toward conservative revisions and difficult to shield from non-scientific influences. It is suggested that rather making further attempts to develop a general monolithic classification that meets all needs, consideration be given to developing a more flexible and multifaceted framework that combines diagnosis and assessment.