Diagnosing Personality Disorders

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). Some personality traits are harmful to both oneself and to others. These are the dysfunctional traits. Often they cause discomfort and the person bearing these traits is unhappy and self-critical. This is called ego-dystony. At other times, even the most pernicious personality traits are happily endorsed and even flaunted by the patient. This is called "ego-syntony".
The Diagnostic and Statistical Manual (DSM) describes 12 ideal "prototypes" of personality disorders. It provides lists of seven to nine personality traits per each disorder. These are called "diagnostic criteria". Whenever five of these criteria are met, a qualified mental health diagnostician can safely diagnose the existence of a personality disorder.
But important caveats apply.
No two people are alike. Even subjects suffering from the same personality disorder can be worlds apart as far as their backgrounds, actual conduct, inner world, character, social interactions, and temperament go.
Diagnosing the existence of a personality trait (applying the diagnostic criteria) is an art, not a science. Evaluating someone's conduct, appraising the patient's cognitive and emotional landscape, and attributing motivation to him or her, is a matter of judgment. There is no calibrated scientific instrument that can provide us with an objective reading of whether one lacks empathy, is unscrupulous, is sexualizing situations and people, or is clinging and needy.
Regrettably, the process is inevitably tainted by value judgments as well. Mental health practitioners are only human (well, OK, some of them are...:o)). They hail from specific social, economic, and cultural backgrounds. They do their best to neutralize their personal bias and prejudices but their efforts often fail. Many critics charge that certain personality disorders are "culture-bound". They reflect our contemporary sensitivities and values rather than invariable psychological entities and constructs.
Thus, someone with the Antisocial Personality Disorder is supposed to disrespect social rules and regard himself as a free agent. He lacks conscience and is often a criminal. This means that non-conformists, dissenters, and dissidents can be pathologized and labeled "antisocial". Indeed, authoritarian regimes often incarcerate their opponents in mental asylums based on such dubious "diagnoses". Moreover, crime is a career choice. Granted, it is a harmful and unpalatable one. But since when is one's choice of vocation a mental health problem?
If you believe in telepathy and UFOs and have bizarre rituals, mannerisms, and speech patterns, you may be diagnosed with the Schizotypal Personality Disorder. If you shun others and are a loner, you may be a Schizoid. And the list goes on.
To avoid these pitfalls, the DSM came up with a multi-axial model of personality evaluation.