Hi Brookezee,
A lot of members have asked the same question about partners or loved ones who seem to simultaneously exhibit traits from two or more personality disorders.
One explanation is comorbidity - the simultaneous presence of two chronic diseases or conditions in a patient - no uncommon in people suffering from personality disorders. This overlapping of symptoms or behavioural traits from distinct personality disorders can be very confusing for sufferers, family members and even professionals seeking an accurate diagnosis.
But there are a number of health professionals who feel that comorbidity is one of the biggest problems with DSMIV diagnostic criteria for personality disorders. Professor Peter Tyrer, a psychiatrist, an expert on personality disorders and former editor of the British Journal of Psychiatry - imperial.ac.uk/people/p.tyrer - discusses some of the challenges of diagnosing and categorising personality disorders
www.bjp.rcpsych.org/content/179/1/81#ref-12I've spoken to a number of therapists who no longer use the NPD or BPD labels because they feel that they are unhelpful for effective treatment. The DSMV made attempts to reform or clarify the diagnostic criteria for personality disorders and some of their proposals proved be very controversial, one of which was the removal of Narcissistic Personality Disorder as well as four other from the DSMV.
www.nytimes.com/2010/11/30/health/views/30mind.html It's worth reading the wiki entry on the Diagnostic and Statistical Manual of Mental Disorders for more context.
https://en.wikipedia.org/wiki/Diagnostic_and_Statistical_Manual_of_Mental_DisordersThe DSM is not the only organisation that provides a classification system for mental disorders. The ICD, the International Classification of Diseases is a global organisation and part WHO also publishes a classification system.
www.apa.org/monitor/2009/10/icd-dsm.aspxIn February 2015 the ICD published a new proposed diagnostic model for diagnosing personality disorders. The opening paragraph states "Personality disorders are common and ubiquitous in all medical settings, so every medical practitioner will encounter them frequently. People with personality disorder have problems in interpersonal relationships but often attribute them wrongly to others. No clear threshold exists between types and degrees of personality dysfunction and its pathology is best classified by a single dimension, ranging from normal personality at one extreme through to severe personality disorder at the other. The description of personality disorders has been complicated over the years by undue adherence to overlapping and unvalidated categories that represent specific characteristics rather than the core components of personality disorder."
If you're interested in reading more I can send you the article
Reforming