Self-injurious behavior: a review of the behavior and biology of self-mutilation. OBJECTIVE: The authors describe the clinical characteristics of self-injurious behavior, giving special emphasis to self-injurious behavior occurring among individuals with character disorders. DATA COLLECTION: They review data suggesting the involvement of serotonergic, dopaminergic, and opiate neurotransmitter systems in the expression of self-injurious behavior. FINDINGS: Self-injurious behavior occurs among mentally retarded individuals, psychotic patients, prison populations, and individuals with severe character disorders. Although theoretical psychological models of self-injurious behavior are helpful in understanding the patient's experience of self-injury, no generally useful therapeutic approach has yet evolved from these models. Data derived from animal models and treatment studies suggest the involvement of opiatergic and dopaminergic mechanisms in self-injury among the mentally retarded. Serotonergic influences on self-injurious behavior may be present in varying forms of this behavior. The scientific literature on the benefits of pharmacological agents for mentally retarded individuals is beset with a number of problems. Support is emerging, however, for the use of lithium and carbamazepine with self-injuring mentally retarded patients, and some behavioral interventions appear to be successful for mentally retarded individuals. Self-injuring patients with borderline personality disorder may benefit from milieu treatment. CONCLUSIONS: Although no form of treatment has yet been demonstrated to be of general benefit, the literature suggests that therapeutic trials with dopamine antagonists, serotonin reuptake inhibitors, and opiate antagonists may be of value. 