Cannabis Extract and THC Both Significantly Reduced Urinary Incontinence in MS Patients | Research

The takeaway

A substudy from the 630-patient CAMS trial found cannabis extract reduced urinary incontinence episodes by 38% and THC by 33%, both significantly better than placebo's 18% reduction, in MS patients.

Read this if you have MS-related bladder problems and want to know whether cannabis-based treatments might help.

Cannabis extract reduced incontinence episodes by 38% vs. placebo's 18% (P = 0.005)

What the researchers found

This was a substudy of the large Cannabinoids in Multiple Sclerosis (CAMS) trial, which had randomized 630 MS patients across 33 UK centers to cannabis extract, THC, or placebo. Participants completed incontinence diaries.

All three groups showed significant reductions in urge incontinence episodes from baseline to end of treatment. However, both active treatments were significantly superior to placebo: cannabis extract reduced episodes by 38% (P = 0.005 vs. placebo), and THC reduced episodes by 33% (P = 0.039 vs. placebo), compared to placebo's 18% reduction.

Notably, this positive finding contrasted with the main CAMS study result, where no difference was seen in the primary outcome of spasticity (Ashworth scale). The authors suggested this indicated a genuine clinical effect of cannabis on bladder function in MS.

Why it matters

Urinary incontinence is a common and debilitating MS symptom with limited treatment options. Finding significant benefits from both cannabis extract and THC in this large, rigorous trial setting provided stronger evidence than most previous studies, particularly since the main trial's primary outcome (spasticity) was negative.

The numbers in context

630 patients in main CAMS study. Incontinence episode reduction: cannabis extract 38%, THC 33%, placebo 18%. Cannabis extract vs. placebo: P = 0.005. THC vs. placebo: P = 0.039.

How the study worked

Substudy of the multicenter CAMS RCT. From 630 MS patients randomized to oral cannabis extract, THC, or placebo across 33 UK centers. Participants completed incontinence diaries. Episode rates adjusted for baseline imbalance.

What this study cannot tell us

This was a substudy, not the primary analysis. Not all 630 patients completed incontinence diaries. The adjustment for baseline imbalance was necessary but adds analytical complexity. The mechanism of cannabinoid effects on bladder function was not directly studied.

How to read the evidence

Substudy from a large, well-designed multi-center RCT. Strong methodology but secondary analysis rather than the primary outcome of the parent trial.

When this study was published

Published in 2006. Cannabinoid effects on bladder function have been further studied since then, with some evidence supporting this finding.

The bigger picture

The finding that cannabinoids helped bladder symptoms more than spasticity in the same patient population suggests different MS symptoms may respond differently to cannabinoid treatment. Bladder function is regulated in part by cannabinoid receptors in the urinary tract, providing a biological rationale for this effect.

Questions still open

Is the bladder effect sustained with long-term use? Could cannabinoids be developed specifically for neurogenic bladder dysfunction?

Common questions

Can cannabis help with MS bladder problems?

In this substudy of 630 MS patients, both cannabis extract and THC significantly reduced urinary incontinence episodes compared to placebo (38% and 33% reduction vs. 18%). This suggests a genuine clinical benefit for bladder symptoms.

Why did cannabis help bladder symptoms but not spasticity in this trial?

The main CAMS trial found no significant effect on spasticity (Ashworth scale), but this bladder substudy showed clear benefits. Different MS symptoms may respond differently to cannabinoids, possibly because different tissues have different cannabinoid receptor distributions and sensitivities.

Read the original research

The effect of cannabis on urge incontinence in patients with multiple sclerosis: a multicentre, randomised placebo-controlled trial (CAMS-LUTS).

International urogynecology journal and pelvic floor dysfunction, 17(6), 636-41

View on PubMed ↗

Citation

Freeman, R M; Adekanmi, O; Waterfield, M R; Waterfield, A E; Wright, D; Zajicek, J. (2006). The effect of cannabis on urge incontinence in patients with multiple sclerosis: a multicentre, randomised placebo-controlled trial (CAMS-LUTS).. International urogynecology journal and pelvic floor dysfunction, 17(6), 636-41.