The idea that legal cannabis can help address the opioid crisis has generated much hope and enthusiasm.

Opioid misuse has declined in recent years at the same time that cannabis use has been increasing, with many states liberalizing marijuana laws.

Based on recent research, some advocates have been promoting this connection, arguing that easier access to marijuana reduces opioid use and, in turn, overdose deaths.

A new study urges caution. Sometimes appearances — or statistics — can be deceiving.

Why people were so hopeful

It’s plausible that marijuana can help reduce pain. Systematic reviews show that certain compounds found in marijuana or synthetically produced cannabinoids do so, at least for some conditions. So some people who might otherwise seek out opioid painkillers could use medical marijuana instead.