 Depression in patients with schizophrenia may also be caused by substance abuse, which is fairly common among those suffering from schizophrenia, as depressants such as alcohol and cannabis can relax the patient.Furthermore, with what little information is currently known about post-schizophrenic depression, the onset may be caused by not giving patients with schizophrenia antipsychotic medications.After being taken off of antipsychotic medication, schizophrenic patients' antidepressant medication had to be increased, while those under antipsychotic medication reported suffering fewer depressive symptoms, further giving reason to believe that a lack of antipsychotic medication in earlier stages of schizophrenia may lead to post-schizophrenic depression.