Self-injury was studied in 64 adults with borderline personality disorder, major depression, or chronic paranoid schizophrenia. Subjects were rated according to acute depression, chronic depression, self-injurious behaviors, and neurocognitive deficits, as measured by cognitive function examination. Borderline patients showed more self-injurious behaviors and more chronic depressive symptoms than the major depression or schizophrenia groups. Self-injury was not significantly correlated with acute or chronic depression in any group, but self-injury was correlated with neurocognitive deficits in borderline and schizophrenic groups. The results are explained in the context of a neurocognitive model of psychotic thought process in borderline disorder and schizophrenia.