Schizoid personality disorder has a complicated past. It was originally conceptualized as the personality type associated with schizophrenia. However, the Diagnostic and Statistical Manual of Mental Disorders states that schizoid personality disorder should not be diagnosed if the pattern of behavior occurs exclusively during the course of schizophrenia. But this does not mean that the two cannot co-occur. Schizoid personality disorder most often co-occurs with schizotypal, paranoid, and avoidant personality disorders. At the turn of the twentieth century, schizoid personality disorder was described as a trait-like variant of schizophrenia. Others described it as “shut-in personality,” “schizoidie,” and even as “autistic personality.” The term schizoid was also used in broader terms to identify socially withdrawn patients who had great difficulty with intimacy and peculiar behavior now associated with schizotypal personality disorder.
However schizoid personality disorder can be differentiated from other disorders. Schizoid personality disorder is different from schizotypal personality disorder in that schizotypal personality disorder lacks the cognitive and perceptual distortions that are associated with schizoid
In the process of therapy, the development of rapport and a trusting therapeutic relationship will most likely be a slow, gradual process that may not ever fully develop as in seeing people with other disorders. This is because people who suffer from this disorder often maintain a social distance with people in their lives, even those close to them. The therapist should work to help ensure the client's security in the therapeutic relationship. They should also acknowledging the client's boundaries are important and the therapist should not attempt to confront the client on these types of issues.