Diagnosis | Right Decisions

The current major diagnostic systems are the International Classification of Diseases, Tenth Edition or ICD-10 (World Health Organisation, 1993), and the Diagnostic and Statistical Manual-5 or DSM-5 (American Psychiatric Association, 2014). Both have a set of general criteria for diagnosis of personality disorder and sets of criteria for a number of specific personality disorders.

There are slight differences in the categorisation of the two diagnostic systems but they are currently broadly similar. ICD-11 (due in 2017) is likely to fundamentally change the diagnostic process, switching to a simpler dimensional system, with greater scientific validity and clinical utility. However, until this happens, it is recommended that the current ICD-10 diagnoses are used. The exception is that DSM criteria should be used for the diagnosis of borderline personality disorder. This is because there the evidence base relating to treatments for Borderline Personality Disorder is based upon DSM-IV criteria rather than the ICD-10 equivalent diagnosis, Emotionally Unstable Personality Disorder.

In clinical practice, co-occurrence of several different specific personality disorders in the same individual is common. For example, only one in ten patients meeting criteria for borderline personality disorder only meet criteria for that specific personality disorder. In cases where the full criteria for more than one specific personality disorder are met, the diagnosis of F60.9 Personality disorder, unspecified should be made, with the prominent components specified. For example: F60.9 Personality disorder, unspecified (moderate, with borderline, dependent and anankastic components). It is useful, whatever the diagnosis, to indicate the severity as mild, moderate or severe. ICD-11 is likely to use “mild” to describe personality disorder with disturbance in only one higher trait domain, “moderate” for those with disturbance in two or more higher trait domains, and “severe” is likely to be defined as those with disturbance in two or more higher trait domains along with significant risk to themselves or others.

The diagnosis F61.0. Mixed Personality Disorder should be reserved for situations where the general criteria for personality disorder are met, but the full criteria are not met for any specific personality disorder category, although features from more than one specific category are present.

This phenomenon of co-occurrence underlines some of the shortcomings of the current classification systems. The DSM system has attempted to address the issue of co-occurrence of specific personality disorders by describing 3 clusters of personality disorders which are said to co-occur most frequently. While having some clinical usefulness, there is no robust empirical basis to these clusters:

• Cluster A Odd/eccentric: schizoid, paranoid and schizotypal personality disorders
• Cluster B Dramatic: borderline (emotionally unstable), narcissistic, histrionic and antisocial personality disorders
• Cluster C Anxious/avoidant: obsessive-compulsive (anakastic), avoidant (anxious) and dependent personality disorders

It is worth noting that for patients under the age of eighteen, clinicians are cautioned against making a diagnosis of personality disorder. However, undoubtedly patients under the age of eighteen do present with personality-related conditions. In such situations terms such as “emergent personality disorder” or “evolving personality disorder” are sometimes used. If the clinician is unclear whether personality disorder is present or not, a presentation can still be referred to as a “personality-related condition”, or particular traits can be described. The primary aim in being clear about the role of personality versus major mental illness in such situations is to avoid inappropriate, unnecessary and sometimes harmful treatments and to enable appropriate early intervention.