Psychological Medicine

Original Articles

Specialized psychosocial treatment plus treatment as usual (TAU) versus TAU for patients with cannabis use disorder and psychosis: the CapOpus randomized trial

C. R. Hjorthøja1 c1, A. Fohlmanna1, A.-M. Larsena1, C. Gluuda2, M. Arendta3 and M. Nordentofta1

a1 Copenhagen University Hospital, Mental Health Centre Copenhagen, Research Unit, Copenhagen NV, Denmark

a2 Copenhagen Trial Unit, Department 33.44, Rigshospitalet, Copenhagen Ø, Denmark

a3 Unit for Psychiatric Research, Aalborg Psychiatric Hospital, Aarhus University Hospital, Denmark


Background Cannabis abuse in psychotic patients is associated with rehospitalizations, reduced adherence and increased symptom severity. Previous psychosocial interventions have been ineffective in cannabis use, possibly because of low sample sizes and short interventions. We investigated whether adding CapOpus to treatment as usual (TAU) reduces cannabis use in patients with cannabis use disorder and psychosis.

Method A total of 103 patients with psychosis and cannabis use disorder were centrally randomized to 6 months of CapOpus plus TAU (n = 52) or TAU (n = 51). CapOpus consisted mainly of motivational interviewing and cognitive behaviour therapy (CBT). TAU was targeted primarily at the psychotic disorder. The primary outcome was self-reported days with cannabis use in the preceding month.

Results Pre-randomization cannabis use frequency was 14.9 [95% confidence interval (CI) 12.7–17.1] days/month. Post-treatment, the ratio of days/month with cannabis use in CapOpus versus TAU was 0.76 (95% CI 0.38–1.50) (p = 0.42), and 0.80 (95% CI 0.21–3.10) (p = 0.75) at the 4-month follow-up. From 46.4 (95% CI 36.4–56.3) monthly joints pre-randomization, consumption fell to 27.3 (95% CI 12.6–41.9) joints in CapOpus and 48.2 (95% CI 31.8–64.6) in TAU (p = 0.06). Follow-up amounts were 28.4 (95% CI 13.5–43.2) and 41.6 (95% CI 25.2–58.0) joints (p = 0.23). Several subgroup analyses suggested benefits of CapOpus.

Conclusions CapOpus did not reduce the frequency, but possibly the amount, of cannabis use. This is similar to the findings of previous trials in this population. Implementation of CapOpus-type interventions is thus not warranted at present but subgroup analyses call for further trials.

(Received May 24 2012)

(Revised August 15 2012)

(Accepted August 23 2012)

(Online publication October 08 2012)

Key words

  • Cannabis;
  • dual diagnosis;
  • psychosis;
  • randomized clinical trial;
  • schizophrenia


c1 Address for correspondence: C. R. Hjorthøj, Ph.D., M.Sc., Copenhagen University Hospital, Mental Health Centre Copenhagen, Research Unit, Bispebjerg Bakke 23, Building 13A, DK-2400 Copenhagen NV, Denmark. (Email: