Long-term assessment of the cognitive effects of nabiximols in patients with multiple sclerosis: A pilot study

Moderate to severe spasticity is commonly reported in Multiple Sclerosis (MS) and its management is still a challenge. Cannabinoids were recently suggested as add-on therapy for the treatment of spasticity and chronic pain in MS but there is no conclusive scientific evidence on their safety, especially on cognition and over long periods. The aim of this prospective pilot study was to assess the long-term effects of a tetrahydrocannabinol-cannabidiol (THC/CBD) oromucosal spray (Sativex®) on cognition, mood and anxiety.

An extensive and specific battery of neuropsychological tests (Symbol Digit Modalities Test-SDMT, California Verbal Learning Test-CVLT, Brief Visuospatial Memory Test-BVMT; PASAT-3 and 2; Free and Cued Selective Remind Test-FCSRT, Index of Sensitivity of Cueing-ISC) was applied to longitudinally investigate different domains of cognition in 20 consecutive MS patients receiving Sativex for spasticity. The primary endpoint was to assess any variation in cognitive performance. Secondary outcomes regarding mood and anxiety were investigated by means of Beck Depression Inventory (BDI) and Hamilton Anxiety Rating Scale (HAM-A). Any change in patients' spasticity was evaluated using the 0-10 Numerical Rating Scale (NRS).

Twenty per protocol patients were followed up and evaluated at baseline, 6 and 12 months. Domains involving processing speed and auditory verbal memory significantly improved within the first 6 months of therapy (SDMT: p < 0.001; CVLT: p = 0.0001). Mood and anxiety did not show any significant variation. Additionally, the NRS score significantly improved since the beginning (p < 0.0001).

These results are encouraging in supporting possible long-term benefits of Sativex on cognition and a wider role than symptom alleviator. Further studies on larger groups of patients would be necessary in order to test this intriguing possibility.