April 27, 2021 | News | Living with MS MS Research MS Treatments

Caution advised with cannabis use for depression

Cannabis products are a popular alternative remedy for people with multiple sclerosis aided in part by their legalization in many jurisdictions. Medical and recreational use is legal in Canada. In the U.S., possession and use is illegal under federal law, but a patchwork of state laws permit recreational use in 17 states, medical use is legal in 36 states, and use of low THC products in another 12 states. Pharmaceutical cannabinoids, such as Marinol and Syndros, are also approved for medical use by the FDA.

A recent survey of people treated at an MS clinic in British Columbia found that 19% used cannabis on a daily basis, 6% used it weekly and 4% used it monthly; 50% of people said they never used it (Schabas and colleagues. Mult Scler J Exp Transl Clin 2019;5:2055217319869360). Most smoked or vaped cannabis, while comparatively few used prescription cannabinoids.

The people who are more likely to use cannabis are those who have more severe MS. The best evidence in favour of cannabis is for symptoms such as chronic pain or spasticity (muscle stiffness) (Nielsen and colleagues. Curr Neurol Neurosci Rep 2018;18:8).

However, a new study cautions about using cannabis to manage symptoms of depression or anxiety (Feinstein and colleagues. Mult Scler 2021;27:636-639). The University of Toronto study evaluated symptoms of depression in 40 people with MS who were suffering from cognitive impairments. At the start of the study, all of the participants were smoking cannabis on a daily basis. For the one-month study, one-half of the group continued with their usual cannabis use and one-half were asked to stop. What the researchers found was the symptoms of depression improved in the group that quit cannabis for a month. This improvement in mood may be related to cognitive functioning. The same researchers previously found that cognitive test scores were better if people had been off cannabis for a month or so (Feinstein and colleagues. Brain 2019;142:2800-2812).

These studies suggest that cannabis should be viewed like other medications. It can be helpful for some MS symptoms, such as pain or muscle stiffness, which may decrease reliance on other pain or spasticity drugs. But it will be less helpful for other MS symptoms, such as depression or anxiety. And however valuable symptomatic medications can be, they cannot substitute for medications intended to target the MS disease processes, such as disease-modifying therapies.

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