Diagnostic Criteria
A pervasive pattern of detachment from social relationships and a restricted range of expression of emotions in interpersonal settings, beginning by early adulthood and present in a variety of contexts, as indicated by four (or more) of the following:
neither desires nor enjoys close relationships, including being part of a family
almost always chooses solitary activities
has little, if any, interest in having sexual experiences with another person
takes pleasure in few, if any, activities
lacks close friends or confidants other than first-degree relatives
appears indifferent to the praise or criticism of others
shows emotional coldness, detachment, or flattened affectivity
Does not occur exclusively during the course of Schizophrenia, a Mood Disorder With Psychotic Features, another Psychotic Disorder, or a Pervasive Developmental Disorder and is not due to the direct physiological effects of a general medical condition.
Note: If criteria are met prior to the onset of Schizophrenia, add "Premorbid," e.g., "Schizoid Personality Disorder (Premorbid)."
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Differential Diagnosis*
Delusional Disorder; Schizophrenia; and Mood Disorder With Psychotic Features; Autistic Disorder; Asperger's Disorder; Personality Change Due to a General Medical Condition; symptoms that may develop in association with chronic substance use; Schizotypal Personality Disorder; Paranoid Personality Disorder; Avoidant Personality Disorder; Obsessive-Compulsive Personality Disorder. (Mentalhealth.com)
*Differential Diagnosis means all the other illnesses that must be ruled out before a Dx of an illness may be made. It is just as much of the diagnosis as meeting the criteria is and cannot be ignored.