The DSM is categorical. It states that personality disorders are "qualitatively distinct clinical syndromes"

Clinical Features of the Narcissistic Personality Disorder

Recent headline: “Road Rage may be due to medical condition called Intermittent Explosive Disorder (IED)” WHAT IS THE SCIENCE BEHIND THIS? The study, reported in the June (2006) issue of the Archives of General Psychiatry was based on a national face-to-face survey of 9,282 U.S. adults who answered diagnostic questionnaires in 2001-03. It was funded by the National Institute of Mental Health. Results? About 5 percent to 7 percent of the nationally representative sample...

Anxiety Disorders – and especially Generalised Anxiety Disorder (GAD) – are often misdiagnosed as Narcissistic Personality Disorder (NPD).

The Second Law of Thermodynamics predicts the gradual energetic decay of physical closed systems ("entropy"). Arguably, the Universe as a whole is precisely such a system.

Asperger's Disorder is often misdiagnosed as Narcissistic Personality Disorder (NPD), though evident as early as age 3 (while pathological narcissism cannot be safely diagnosed prior to early adolescence).

Depression. It’s that disorder that has become seemingly fashionable amongst celebrities, up there with ‘exhaustion.’ Because to put the label of ‘depressed’ on oneself is to excuse not wanting to...

Personality traits are enduring, usually rigid patterns of behavior, thinking (cognition), and emoting expressed in a variety of circumstances and situations and throughout one's life (typically from early adolescence onward).

In the DSM, there are 10 distinct personality disorders.