The effects of clozapine versus haloperidol on measures of impulsive aggression and suicidality in chronic schizophrenia patients: an open, nonrandomized, 6-month study

J Clin Psychiatry. 2003 Jul;64(7):755-60. doi: 10.4088/jcp.v64n0703.


Background: The risk of suicide for schizophrenia patients is 20 to 50 times higher than that for the general population. Long-term treatment with clozapine, an atypical antipsychotic, has been shown to reduce the rate of suicide by 80% to 85%. The goal of the present study was to examine whether clozapine's effect on the reduction of suicidal behavior in chronic schizophrenic patients could be due to a reduction in impulsive-aggressive behavior.

Method: 44 patients with chronic DSM-IV schizophrenia were treated with clozapine or haloperidol decanoate in an open prospective 6-month trial. Changes in measures of suicidality, impulsiveness, aggression, depressed mood, and positive and negative symptoms were assessed at baseline and at 6 months.

Results: The clozapine-treated group (N = 18) had a significantly greater reduction on all outcome measures compared with the haloperidol decanoate-treated group (N = 26). Only in the clozapine-treated group did the reduction in measures of suicidality correlate significantly with a reduction in impulsiveness and aggression. The reductions in suicidality and impulsive aggression were not significantly correlated with reductions in depressed mood or positive and negative symptom scores in either group.

Conclusion: These data suggest that the reduction in suicidality following long-term clozapine treatment may be related to a reduction in impulsiveness and aggression.

Publication types

  • Clinical Trial
  • Comparative Study
  • Controlled Clinical Trial

MeSH terms

  • Adolescent
  • Adult
  • Aggression / drug effects*
  • Antipsychotic Agents / administration & dosage
  • Antipsychotic Agents / therapeutic use*
  • Chronic Disease
  • Clozapine / administration & dosage
  • Clozapine / pharmacology*
  • Clozapine / therapeutic use*
  • Diagnostic and Statistical Manual of Mental Disorders
  • Disruptive, Impulse Control, and Conduct Disorders / diagnosis
  • Disruptive, Impulse Control, and Conduct Disorders / drug therapy*
  • Drug Administration Schedule
  • Female
  • Haloperidol / administration & dosage
  • Haloperidol / pharmacology*
  • Haloperidol / therapeutic use*
  • Humans
  • Male
  • Middle Aged
  • Schizophrenia / diagnosis
  • Schizophrenia / drug therapy*
  • Suicide, Attempted / psychology*


  • Antipsychotic Agents
  • Clozapine
  • Haloperidol