Introduction

Both DSM-IV and ICD-10 have classifications for a range of personality disorders (PD). Both have a categorical structure to classification and have the same strengths and weaknesses. The research covered in this chapter will allude primarily to DSM-IV-TR classifications but is directly relevant to considerations on ICD-10 classification. It should be noted that there has recently been a review of ICD-10 classifications, that takes account of an intellectual disabilities (ID) perspective, DC-LD (Royal College of Psychiatrists, 2001). From the viewpoint of PD there are interesting basic alterations in DC-LD. Firstly, it recommends that, because of developmental delay in these individuals, diagnosis should not be made until at least 21 years of age. In addition, DC-LD requires the initial confirmation of PD unspecified, before progressing to more general diagnoses of PD. Personality disorder unspecified requires that the characteristics must not be a direct consequence of the person's ID and also states specifically that there must be associated significant problems in occupational and/or social functioning. Therefore, the impact of personality on the person's general social and occupational function is explicitly considered as a requirement for diagnosis (see also Chapter 1 by Sturmey).

The DSM-IV-TR (American Psychiatric Association, 2000) has extensive trait descriptions for ten specific PDs in three clusters. Cluster A includes paranoid PD (suspiciousness and distrust); schizoid PD (detachment from social relationships, a restricted range of emotional expression); and schizotypal PD (acute discomfort in close relationships, eccentricities of behaviour including magical control and idiosyncratic speech).