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Trial shows no clear benefit from cannabis for patients with MS

London -- The three year CAMS (cannabis in multiple sclerosis) trial,involving more than 600 patients in the United Kingdom, hasyielded no definitive verdict on whether the drug can ease thesymptoms of multiple sclerosis. The study, funded by the MedicalResearch Council, was published in last week's issue of theLancet ( 2003;362: 1517-26).

Fifteen weeks' treatment with oral capsules containing eitherwhole cannabis extract or tetrahydrocannabinol (THC), the drug'sprincipal active ingredient, did not produce a significant improvementin spasticity as measured by the widely used Ashworth scale.

But in face to face interviews, patients assigned to the treatmentarm of the double blinded trial were more likely than thosereceiving placebo to report a subjective improvement in symptoms.The participants reported significant improvements in pain,sleep quality, spasms, and spasticity, though not in irritability,depression, tiredness, tremor, or energy. The researchers foundthat patients taking the cannabis derivative showed an improvementin the time taken to walk 10 metres.

The proportion of patients reporting improvements in spasticitywas 61% in the arm receiving cannabis extract (n=121, 95% confidenceinterval 55% to 68%), 60% in the arm receiving THC (n=108, 53%to 67%), and 46% (n=91, 39% to 53%) in the placebo arm.

The lead researchers, John Zajicek, consultant neurologist atPlymouth Hospitals NHS Trust, and Professor Alan Thompson, consultantneurologist at the National Hospital for Neurology and Neurosurgery,London, cautioned that about three quarters of the patientsgiven cannabis had guessed they were taking active medication,and half of those receiving placebo had guessed that they werenot receiving cannabis.

Dr Zajicek said: "The primary aim of the trial was to measure,as objectively as possible, the actual physical changes in limbspasticity in MS patients, and we found no evidence of this.

"Although we based the study around spasticity, we also wantedto capture any treatment effects among the other important symptomsdescribed by people with MS. When patients were asked to describehow they felt that their symptoms, including spasticity, hadbeen affected, the picture was very different. They felt someof the impact of their painful and distressing symptoms hadbeen eased.

"We did see a high placebo effect in this trial and it may beindicative of how much patients gain by taking part in clinicaltrials, irrespective of the treatment they are given. Patientsexperienced very few side effects from the treatments, and,given that how a patient feels is an important part of improvinghealth, cannabis based treatments may be of benefit to somepatients."

Mike Barnes, professor of neurological rehabilitation at theUniversity of Newcastle, said: "The results of this study aremixed, but the positive aspects undoubtedly outweigh the negatives.It is my hope that in the near future, people with MS will haveaccess to cannabis derived medicines on the NHS."

BMJ 2003;327:1128 (15 November).