Schizophrenia Patients Accepted Low-THC Cannabis but Preferred Their Regular High-Potency Product | Research

The takeaway

In a crossover pilot study, 12 male schizophrenia patients who smoked high-potency cannabis appreciated low-THC substitute variants but preferred their usual cannabis, with complaints about insufficient strength and short duration of effects.

Psychiatrists, harm reduction specialists, dual-diagnosis treatment providers.

64% found the low-THC cannabis not strong enough, but both substitute variants were still appreciated, suggesting cannabis substitution is feasible.

What the researchers found

Both substitute variants (low THC/no CBD and low THC/high CBD) were appreciated by patients. However, they preferred their usual high-potency cannabis. The low THC/high CBD variant was reported as too short-acting by 32% and not strong enough by 36%. The low THC variant was reported as not strong enough by 64%.

Why it matters

This study explores whether cannabis substitution (replacing high-potency with lower-risk products) is feasible in schizophrenia patients. While acceptance was positive, the preference for usual cannabis suggests substitution may work better as part of a gradual reduction strategy.

The numbers in context

12 male patients. Three cannabis types: usual high-potency, low THC/no CBD, and low THC/high CBD. 64% found low THC variant not strong enough. 36% found low THC/high CBD not strong enough. 32% found low THC/high CBD effects too short.

How the study worked

Crossover design with 12 male schizophrenia patients who daily smoked high-potency cannabis. Each patient smoked their usual cannabis on two occasions (unblinded) and each substitute variant on two occasions (blinded, randomized).

What this study cannot tell us

Very small sample (n=12). All male. Short-term preference assessment does not indicate long-term compliance. Unblinded comparison to usual cannabis biases preference. No clinical outcome measures.

How to read the evidence

Preliminary - very small pilot (n=12) with short-term assessment and no clinical outcome measures.

When this study was published

Published in 2018.

The bigger picture

Cannabis substitution could be a harm reduction strategy for psychosis patients who cannot or will not stop using cannabis entirely. This pilot suggests such substitution is feasible, even if patients prefer their usual product.

Questions still open

Would longer substitution periods lead to acceptance as patients adjust? Could partially reduced THC (rather than very low THC) be a more acceptable middle ground? Would clinical benefits (reduced psychosis symptoms) motivate continued substitution use?

Common questions

Can people with schizophrenia switch to lower-potency cannabis?

This pilot study of 12 patients found that while they accepted lower-THC cannabis variants, they preferred their usual high-potency product. A larger, longer study was deemed feasible based on these results.

What is cannabis substitution therapy?

Cannabis substitution replaces high-potency street cannabis (high THC, low CBD) with lower-risk variants containing less THC and/or more CBD. The goal is harm reduction in patients who continue using cannabis despite clinical advice to stop.

Read the original research

Acceptance of pharmaceutical cannabis substitution by cannabis using patients with schizophrenia.

Harm reduction journal, 15(1), 47

View on PubMed ↗Publisher’s paper ↗

Citation

van Amsterdam, Jan; Vervloet, Jojanneke; de Weert, Gerdien; Buwalda, Victor J A; Goudriaan, Anna E; van den Brink, Wim. (2018). Acceptance of pharmaceutical cannabis substitution by cannabis using patients with schizophrenia.. Harm reduction journal, 15(1), 47. https://doi.org/10.1186/s12954-018-0253-7