Some cannabis products with psychoactive ingredients can help improve short-term chronic pain, but their side effects remain a concern, according to a review of 25 trials and studies.

While opioids are frequently prescribed to manage chronic pain, they demonstrate a little effect on pain overall and are associated with significant adverse effects. Cannabinoid products are a potential alternative and can come from multiple sources, including synthetic, extract, or the whole plant.

The term "cannabinoid" references compounds that are active in cannabis, such as tetrahydrocannabinol (THC) and cannabidiol (CBD). These compounds have previously demonstrated pain-relief properties that vary depending on the ratio of THC to CBD.

Researchers from Oregon Health & Science University in the US reviewed 18 randomised, placebo-controlled trials, comprising 1,740 participants, and seven cohort studies, comprising 13,095 participants, to evaluate the benefits and harms of cannabinoids for chronic pain.

The findings, published in Annals of Internal Medicine, showed that synthetic products with high THC-to-CBD ratios were associated with moderate improvement in pain severity and response but were also associated with an increased risk for sedation and dizziness.

The team also found that small improvements in overall function were demonstrated for products with comparable THC-to-CBD ratios, but no improvements were demonstrated for products with high THC-to-CBD ratios.

However, they determined that evidence for whole-plant products, CBD, and other cannabinoids was limited by serious imprecision and lack of ability to assess consistency and study methodological limitations.

The team also noted that reviewed studies did not evaluate harm outcomes including psychosis, cannabis use disorder, and cognitive deficits, and studies did not include patients who were at higher risk for harm.

In an accompanying editorial, researchers from the University of Michigan Medical School advised clinicians to be willing to provide compassionate guidance to patients who use cannabis products by using a strategy of pragmatism and knowledge of patient experience, known cannabinoid effects, and harm reduction.

The researchers highlight that this review can offer information to clinicians on routes of administration, the effects of CBD versus THC, dosing, and potential adverse effects.