The classificatory model the DSM has been using since 1952 is harshly criticised as woefully inadequate by many scholars and practitioners.

The DSM is categorical. It states that personality disorders are "qualitatively distinct clinical syndromes". But this is by no means widely accepted. The professionals cannot even agree on what constitutes "normal" and how to distinguish it from the "disordered" and the "abnormal". The DSM does not provide a clear "threshold" or "critical mass" beyond which the subject should be considered mentally ill.

Moreover, the DSM's diagnostic criteria are ploythetic. In other words, suffice it to satisfy only a subset of the criteria to diagnose a personality disorder. Thus, people diagnosed with the same personality disorder may share only one criterion or none. This diagnostic heterogeneity (great variance) is unacceptable and non-scientific.

There are five diagnostic axes employed by the DSM to capture the way clinical syndromes (such as anxiety, mood, and eating disorders), general medical conditions, psychosocial and environmental problems, chronic childhood and developmental problems, and functional issues interact with personality disorders. Yet, the DSM's "laundry lists" obscure rather than clarify the interactions between the various axes. As a result, the differential diagnoses that are supposed to help us distinguish one personality disorder from all others, are vague. In psych-parlance: the personality disorders are insufficiently demarcated. This unfortunate state of affairs leads to excessive co-morbidity: multiple personality disorders diagnosed in the same subject. Thus, psychopaths (Antisocial Personality Disorder) are often also diagnosed as narcissists (Narcissistic Personality Disorder) or borderlines (Borderline Personality Disorder).

The DSM also fails to distinguish between personality, personality traits, character, temperament, personality styles (Theodore Millon's contribution) and full-fledged personality disorders. It does not accommodate personality disorders induced by circumstances (reactive personality disorders, such as Milman's proposed "Acquired Situational Narcissism"). Nor does it efficaciously cope with personality disorders that are the result of medical conditions (such as brain injuries, metabolic conditions, or protracted poisoning). The DSM had to resort to classifying some personality disorders as NOS "not otherwise specified", a catchall, meaningless, unhelpful, and dangerously vague diagnostic "category".

One of the reasons for this dismal taxonomy is the dearth of research and rigorously documented clinical experience regarding both the disorders and various treatment modalities. The DSM's other great failing is that many of the personality disorders are "culture-bound". They reflect social and contemporary biases, values, and prejudices rather than authentic and invariable psychological constructs and entities.

The DSM-IV-TR distances itself from the categorical model and hints at the emergence of an alternative: the dimensional approach:

"An alternative to the categorical approach is the dimensional perspective that Personality Disorders represent maladaptive variants of personality traits that merge imperceptibly into normality and into one another".

Yet this is not developed.

The above failings are even more serious when we consider child and adolescent "disorders".