Major mental disorders
In its early phases, schizophrenia can be mistaken for schizoid, schizotypal, paranoid, and borderline personality disorders. Affective disorders can mimic some features of borderline, histrionic, and compulsive personality disorders. Anxiety disorders can share features with compulsive, histrionic, and avoidant personalities. Alcohol and substance abuse disorders may need to be differentiated from antisocial, borderline, and histrionic personalities. Paranoid disorders can sometimes be difficult to differentiate from paranoid, schizotypal, and borderline personalities. Differential diagnostic points are that the major mental disorders tend to have a definite time of onset, that the symptomatology is more severe and causes greater disturbance in everyday functioning, and that specific diagnostic features will be present that transcend the criteria for personality disorders.
Additional personality disorders DSM-III criteria for personality disorders sometimes overlap. “Schizophrenic-like” phenomena, including eccentricity and psychotic experiences, can form part of the picture of paranoid, schizoid, schizotypal, and borderline personalities. Dramatic presentation, emotional outbursts, and erratic behavior can lead to confusion among antisocial, borderline, narcissistic, and histrionic personalities. Impulsivity is found in antisocial, borderline, and histrionic personalities; while anxiety and fearfulness can be part of avoidant, passive-aggressive, dependent, and compulsive behavior.
Medical and neurologic conditions can mimic personality disorders. For example, persons with complex partial seizures with foci in the left temporal lobe can present with excessive orderliness, religiosity, and “viscosity” which might be confused with compulsive personality. Alternatively, they can develop paranoid features or fuzzy thinking suggestive of paranoid or schizotypal personality. Rigid, orderly, and ritualistic behavior mirroring compulsive personality can be part of a dementing process or a sequel of head injury, while irritability, dysregulation of affect, and inappropriate interpersonal behavior in such patients can be confused with borderline personality. Beyond these specific examples, virtually any disease affecting the brain can cause behavioral change suggestive of a personality disorder. The key differential points are that there is a relatively sudden onset and that there are neuropsychological changes indicative of compromised brain function.