BackgroundSubstance use disorders are associated with poorer clinical outcomes in patients with schizophrenia. There is no specific treatment for amphetamine or cannabis use disorder, but methadone and buprenorphine are used as replacement therapy in the treatment of opioid dependence. Our aim was to study whether patients with schizophrenia have received opioid replacement therapy for their opioid use disorder.MethodsThe study sample consisted of 148 individuals diagnosed with schizophrenia who were in involuntary psychiatric treatment as forensic patients in Finland in 2012. The proportion of the study sample with comorbid opioid use disorder having received opioid replacement therapy prior to their forensic psychiatric treatment was compared to the available information of opioid dependent patients in general. The data were collected from forensic examination statements, patient files and other medical registers retrospectively.ResultsOf the study sample, 15.6% (23/148) had a history of opioid use disorder, of whom 8.7% (2/23) had received opioid replacement treatment (95% confidence interval (Cl): 1.1–28.0), even though opioid use disorder had been diagnosed in the treatment system. According the available information the corresponding proportion among patients with opioid use disorder and using substance use disorder services was 30.4% (565/1860, 95% Cl: 28.3–32.5). The fraction of patients receiving opioid replacement therapy was significantly lower among patients with schizophrenia (p = 0.022).ConclusionsOpioid replacement therapy was seldom used among schizophrenia patients who were later ordered to involuntary forensic psychiatric treatment. More attention should be paid to the possible use of opioids when planning treatment for patients with schizophrenia.Trial registrationOur study is not a randomized controlled trial (but a register-based study); thus the trial registration is not applicable.

Cannabis, amphetamine, and opiate use are associated with an increased risk of becoming a forensic psychiatric patient, but no substantial differences were observed among patients with psychosis diagnosis in the relative risk increase for cannabis versus amphetamine versus opiate use, indicating that none of these drugs are uniquely associated with violent offending among mentally ill.

Harmful use or dependence of opioids among patients with schizophrenia is associated with significantly higher risk of hospitalizations than either harmful use or dependence of amphetamine or cannabis.