Cannabis users with psychotic disorders report lower quality of life and worse functioning, with no improvement from starting or stopping | Research

The takeaway

Among nearly 3,000 people with psychotic disorders, cannabis users had lower quality of life and worse psychosocial functioning, and neither starting nor stopping cannabis use changed outcomes over one year.

People with psychotic disorders who use cannabis, psychiatrists, mental health researchers

Starting or stopping cannabis did not change quality of life or functioning within one year

What the researchers found

Cannabis users (11.4%) had significantly lower quality of life (B=-2.93) and worse psychosocial functioning (B=1.03) than non-users. Specifically, they were less satisfied with family relations and finances and showed more aggression, disruptive behavior, and self-harm. Starting or stopping cannabis did not change outcomes within one year.

Why it matters

People with psychosis often report using cannabis to cope or socialize, but this large study found cannabis users actually had worse outcomes across measures. The lack of improvement after stopping suggests accumulated effects from years of use.

The numbers in context

2,994 participants; 36.4% female; mean age 44.4; mean illness duration 17.2 years; 11.4% used cannabis; 255 continuers; 85 discontinuers; 83 starters; 2,571 non-users

How the study worked

Naturalistic cohort study (PHAMOUS) of 2,994 people with psychotic disorders assessed twice (9-15 months apart) between 2014 and 2018, comparing continuers, discontinuers, starters, and non-users.

What this study cannot tell us

Observational design cannot establish causation. Cannabis users may differ from non-users in unmeasured ways. One-year follow-up may be too short to detect changes from stopping. Self-reported cannabis use may be underreported.

How to read the evidence

Large naturalistic cohort study with nearly 3,000 participants and longitudinal follow-up

When this study was published

Published in 2021 using 2014-2018 data from the Netherlands PHAMOUS cohort.

The bigger picture

The finding that neither starting nor stopping cannabis changed outcomes within one year challenges both the idea that cannabis helps people cope with psychosis and the expectation that quitting will produce rapid improvements.

Questions still open

Would longer follow-up after cannabis cessation eventually show improvements? Do the worse outcomes reflect cannabis effects or pre-existing differences between users and non-users? Would targeted interventions addressing the reasons for use be more effective than simple cessation?

Common questions

Does cannabis help people cope with psychosis?

Despite people with psychosis reporting they use cannabis for coping and socializing, this study of nearly 3,000 patients found cannabis users actually had lower quality of life and worse functioning than non-users.

Does quitting cannabis improve outcomes in psychosis?

Not within one year according to this study. Stopping cannabis did not lead to measurable improvements in quality of life or psychosocial functioning, suggesting the negative effects may accumulate over years of use.

Read the original research

The association of cannabis use with quality of life and psychosocial functioning in psychosis.

Schizophrenia research, 228, 229-234

View on PubMed ↗Publisher’s paper ↗

Citation

Bruins, J; Pijnenborg, G H M; Visser, E; Castelein, S. (2021). The association of cannabis use with quality of life and psychosocial functioning in psychosis.. Schizophrenia research, 228, 229-234. https://doi.org/10.1016/j.schres.2020.11.059