Cannabinoids for Tourette syndrome

Cannabinoid medication might be useful in the treatment of the symptoms in patients with Tourette's syndrome. At the present time only two relevant studies have been conducted. Both studies used tetrahydrocannabinol (Δ9THC). In both studies Δ9THC was associated with tic reduction. However the sample size was small and a large number of multiple comparisons were made . There were only 28 participants in total, since eight participants took part in both studies. Possibly the patients who derived the greatest benefit and experienced the least adverse effects would be the most inclined to participate in further studies. There were a high number of drop outs/exclusions in the six week study and it is unclear whether intention to treat analysis (ITT) was performed. The results that are reported are analyses done on the patients who remained in the study on the study medication at the correct dose. In reality, patients do opt not to continue treatment if there is limited efficacy or unpalatable side effects. This introduces attrition bias. Whilst there were some significant results, the authors themselves accept that very few of these results are significant if a Bonferroni correction is performed. It is possible that cannabinoid medication has a beneficial effect which is too weak to be detected using ITT and such a small sample size. There is some weak evidence that cannabinoid medication may have an effect on obsessive compulsive behaviour but the measure used was an addition to the TSSL which has not been validated.There were no data on the effect of Δ9THC on quality of life.There is not enough evidence to support the use of cannabinoids in treating tics and obsessive compulsive behaviour in people with Tourette's syndrome.

 

Authors' conclusions: 

Not enough evidence to support the use of cannabinoids in treating tics and obsessive compulsive behaviour in people with Tourette's syndrome.

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Background: 

Gilles de la Tourette Syndrome (GTS) is a developmental neuropsychiatric disorder characterised by the presence of chronic motor and phonic tics. Drugs currently used in the treatment of GTS either lack efficacy or are associated with intolerable side effects. There is some anecdotal and experimental evidence that cannabinoids may be effective in treating tics and compulsive behaviour in patients with GTS. There are currently no systematic Cochrane reviews of treatments used in GTS. There is one other Cochrane review being undertaken at present, on the use of fluoxetine for tics in GTS.

Objectives: 

To evaluate the efficacy and safety of cannabinoids as compared to placebo or other drugs in treating tics, premonitory urges and obsessive compulsive symptoms (OCS), in patients with GTS.

Search strategy: 

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (in The Cochrane Library Issue 4 2008) , MEDLINE (January 1996 to date), EMBASE (January 1974 to date), PsycINFO (January 1887 to date), CINAHL (January 1982 to date), AMED (January 1985 to date), British Nursing Index (January 1994 to date) and DH DATA (January 1994 to date).

We also searched the reference lists of located trials and review articles for further information.

Selection criteria: 

We included randomised controlled trials (RCTs) comparing any cannabinoid preparation with placebo or other drugs used in the treatment of tics and OCS in patients with GTS.

Data collection and analysis: 

Two authors abstracted data independently and settled any differences by discussion.

Main results: 

Only two trials were found that met the inclusion criteria. Both compared a cannabinoid, delta-9-Tetrahydrocannabinol (Δ9THC), either as monotherapy or as adjuvant therapy, with placebo. One was a double blind, single dose crossover trial and the other was a double blind, parallel group study. A total of 28 different patients were studied. Although both trials reported a positive effect from Δ9THC, the improvements in tic frequency and severity were small and were only detected by some of the outcome measures.

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