Half of people using cannabis for pain experience withdrawal symptoms

More than half of people who use medical marijuana products to ease pain also experience clusters of multiple withdrawal symptoms when they're between uses, according to a new study published in the journal Addiction.

For the study, researchers from Michigan Medicine at the University of Michigan and the VA Ann Arbor Healthcare System reported findings from detailed surveys across two years of 527 Michigan residents. All were participating in the state's system to certify people with certain conditions for use of medical cannabis and had non-cancer-related pain, according to the study.

The researchers asked the patients whether they had experienced any of 15 different symptoms, ranging from trouble sleeping and nausea to irritability and aggression, when they had gone a significant time without using cannabis. The researchers then used an analytic method to empirically group the patients into those who had no symptoms or mild symptoms at the start of the study, those who had moderate symptoms or experienced multiple withdrawal symptoms, and those who had severe withdrawal issues that included most or all the symptoms. They then looked at how things changed over time, surveying the patients one year and two years after their first survey.

At baseline, 41 percent of the study participants fell into the mild symptoms group, 34 percent were in the moderate group, and 25 percent were classed as severe, the study said. Additionally, the researchers found about 10 percent of the patients taking part in the study experienced worsening changes to their sleep, mood, mental state, energy, and appetite over the next two years as they continued to use cannabis.

In the survey, the researchers also asked the patients about how they used cannabis products, how often, and how long they'd been using them, as well as about their mental and physical health, their education, and employment status. Over time, those who had started off in the mild withdrawal symptom group were likely to stay there, but some did progress to moderate withdrawal symptoms.

People in the moderate withdrawal group were more likely to go down in symptoms than up, and by the end of the study the number of the people in the severe category had dropped to 17 percent. In all, 13 percent of the patients had gone up to the next level of symptoms by the end of the first year, and 8 percent had transitioned upward by the end of two years.

Sleep problems were the most common symptom across all three groups, and many in the mild group also reported cravings for cannabis. In the moderate group, the most common withdrawal symptoms were sleep problems, depressed mood, decreased appetite, craving, restlessness, anxiety, and irritability.

The severe withdrawal symptom group was much more likely to report all the symptoms except sweatiness. Nearly all the participants in this group reported irritability, anxiety, and sleep problems. They were also more likely to be longtime and frequent users of cannabis.

Those in the severe group were more likely to be younger and to have worse mental health. Older adults were less likely to go up in withdrawal symptom severity, while those who vaped cannabis were less likely to transition to a lower withdrawal-severity group.

The study didn't assess nicotine use or try to distinguish between symptoms that could also be related to breakthrough pain or diagnosed/undiagnosed mental health conditions during abstinence.

Patients may not recognize that withdrawal symptoms come not from their underlying condition, but from their brain and body's reaction to the absence of substances in the cannabis products they're smoking, vaping, eating, or applying to their skin, the researchers said. When someone experiences more than a few such symptoms, it's called cannabis withdrawal syndrome, and it can mean a higher risk of developing even more serious issues such as a cannabis use disorder, they said.

Many people who turn to medical cannabis for pain do so because other pain relievers haven't worked, the researchers said. The perception of cannabis as "harmless" is not correct, they said. It contains substances called cannabinoids that act on the brain, and that over time can lead the brain to react when those substances are absent. In addition to a general craving to use cannabis, withdrawal symptoms can include anxiety, sleep difficulties, decreased appetite, restlessness, depressed mood, aggression, irritability, nausea, sweating, headache, stomach pain, strange dreams, increased anger, and shakiness, the study said.

The researchers said they hope future research can explore cannabis withdrawal symptoms among medical cannabis patients further, including the impact of different attempts to abstain, different types of use and administration routes, and interaction with other physical and mental health factors. Most research on cannabis withdrawal has been in recreational users, or "snapshot" looks at medical cannabis patients at a single point in time.

Further research could help identify those most at risk of developing problems and reduce the risk of progression to cannabis use disorder, which is when someone uses cannabis repeatedly despite major impacts on their lives and ability to function.