A study has found medicinal cannabis may not ease sleep problems in people with long-term chronic pain.
Researchers from University of Haifa, Israel assessed sleep quality of 128 people aged over 50, with 66 using medicinal cannabis to manage their sleeping problems.
There was no difference between users and non-users in time to get to sleep or how often they woke up early, but most frequent cannabis users had more difficulty with their sleep.
In all, around one in four (24 percent) said they always woke up early and weren't able to get back to sleep; one in five (20 percent) reported always finding it difficult to fall asleep; and around one in five (27 percent) said they woke up during the night.
Many people were developing a tolerance to the drug's sleep-inducing effects. Medicinal cannabis users had used the drug for an average of four years, consuming around 31g a month. About 69 percent of people smoked it, with around 20 percent either using cannabis oil or vapour.
After taking account of potentially influential factors, including average pain score, age, gender, use of other sleep aids or antidepressants, medicinal cannabis users were less likely to wake during the night than non-users.
But researchers said: "These findings have large public health impacts considering the ageing of the population, the relatively high prevalence of sleep problems in this population, along with the increasing use of medicinal cannabis."
Cannabinoids were also associated with a significantly higher risk of side effects, such as drowsiness and dizziness.
The researchers accept that a pain score might not be the best measure to adequately capture the complexity of long-standing pain.
Nevertheless, they concluded that for any medication to be useful, its pros needed to outweigh its cons.
Dr Sharon Sznitman said: "This systematic review provides good evidence that cannabinoids do not have a role in cancer-related pain, and can't therefore be recommended."