Other categories of personality disorders, apart from borderline personality disorder are encountered in clinical practice and these are described and named in DSM-5 but not in ICD-11. The clinical features and diagnostic criteria of all these types are reviewed here. They are grouped into three clusters: Cluster A, the eccentric PDs – which include paranoid, schizoid and schizotypal PDs – and Cluster B, the dramatic group. The most important of these is antisocial personality disorder as well as borderline and histrionic PDs. Cluster C, which are the avoidant or fearful PDs, include avoidant, dependent and obsessive-compulsive types.

Also included in this chapter are a category of conditions known as ’impulse disorders’, where subjects experience an impulse to commit some action which may give them pleasure and are said to be ego-syntonic, yet result in distress to the individual or harm to others. These include gambling, gaming disorder, intermittent explosive disorder, kleptomania and pyromania.

There is strong evidence that schizotypal PD is a schizophrenia-spectrum disorder and an initial diagnosis of schizotypal PD is a strong predictor of future onset of schizophrenia. Despite this evidence, there are questions about whether schizotypal PD or the other Cluster A disorders as currently diagnosed best reflect traits indicating risk for schizophrenia. Further, it is still not empirically resolved to what extent positive schizotypal symptoms reflect genetic risk for schizophrenia. There is strong evidence that schizotypal PD is related to psychological trauma. At the same time, there is evidence that some schizotypal symptoms do appear to reflect variation on normal personality traits, but it is still unresolved whether and how schizotypal symptoms reflect high levels of openness to experience. Cluster A disorders appear to be more common than often assumed and have been associated with poor functioning, but there is a lack of treatment research on these disorders.