Cannabis Users in Psychiatric Units Had Double the Readmission Rate | Research

The takeaway

Among 370 patients admitted to a French involuntary psychiatric unit, those who tested positive for THC were more than twice as likely to be readmitted within a year.

Psychiatrists, dual-diagnosis treatment providers, mental health policymakers

THC-positive psychiatric patients had 2.29x higher odds of one-year readmission

What the researchers found

Of 370 involuntarily admitted psychiatric patients, 130 tested THC-positive. In adjusted analyses, THC-positive status was associated with 2.29 times higher odds of one-year readmission (p=0.0082) and nearly double the odds of benzodiazepine prescriptions at discharge (OR=1.93, p=0.02), but not higher antipsychotic prescriptions.

Why it matters

The strong association between cannabis use and psychiatric readmission suggests that cannabis-using patients may benefit from targeted management strategies that address substance use alongside mental health treatment.

The numbers in context

370 patients; 130 THC-positive (35%); THC+ patients were predominantly young men; adjusted OR for one-year readmission: 2.29 (p=0.0082); adjusted OR for benzodiazepine prescription at discharge: 1.93 (p=0.02); no significant difference in antipsychotic prescriptions.

How the study worked

Retrospective cohort study of all patients admitted to one secure adult psychiatry unit in France in 2016 (n=370), comparing clinical outcomes between THC-positive and THC-negative groups based on urinary drug testing.

What this study cannot tell us

Single-center study in France; retrospective design; urine testing captures only recent use; cannot determine whether cannabis caused worse outcomes or reflects other risk factors; specific to involuntary admission setting.

How to read the evidence

Single-center retrospective cohort with objective drug testing and adjusted analyses, limited by observational design.

When this study was published

Data from 2016 admissions at a French psychiatric unit.

The bigger picture

The finding that cannabis-using psychiatric patients have distinct treatment profiles and worse readmission outcomes supports the development of specialized dual-diagnosis approaches in acute psychiatric settings.

Questions still open

Would integrated substance use treatment during psychiatric admission reduce readmission rates? Why were cannabis-using patients more likely to receive benzodiazepines but not more antipsychotics?

Common questions

Does cannabis use worsen psychiatric outcomes?

In this study, patients who tested positive for cannabis at admission were more than twice as likely to be readmitted within a year. However, the study cannot determine whether cannabis directly caused worse outcomes or was a marker of other risk factors.

How were cannabis-using patients treated differently?

THC-positive patients were nearly twice as likely to be prescribed benzodiazepines at discharge, but antipsychotic prescriptions were similar between groups, suggesting a distinct clinical management profile.

Read the original research

Impact of cannabis use on outcomes of patients admitted to an involuntary psychiatric unit: A retrospective cohort study.

Journal of psychiatric research, 138, 507-513

View on PubMed ↗Publisher’s paper ↗

Citation

Soler, Stephan; Montout, Christine; Pepin, Berengere; Abbar, Mocrane; Mura, Thibault; Lopez-Castroman, Jorge. (2021). Impact of cannabis use on outcomes of patients admitted to an involuntary psychiatric unit: A retrospective cohort study.. Journal of psychiatric research, 138, 507-513. https://doi.org/10.1016/j.jpsychires.2021.04.024