Cannabis can treat both pain and insomnia in people who want to avoid prescription and sleep medications, a study has found.

The study, published in the Journal of Psychoactive Drugs, looked at 1,000 people taking legalised marijuana in an American state.Researchers in the US found that among the 65 per cent of people taking cannabis for pain, 80 per cent found it was very or extremely helpful.

Eighty-two per cent of these people were able to reduce, or stop taking over the counter pain medications and 88 per cent were able to stop taking opioid painkillers.

The study suggested that cannabis could lower opioid use. However, the researchers noted that more needs to be done to understand the potential therapeutic benefits of cannabis.

Traditional over the counter medications and painkillers can help, however they may have serious side effects. Opioids depress the respiratory system, meaning that overdoses may be fatal.

"People develop tolerance to opioids, which means that they require higher doses to achieve the same effect. This means that chronic pain patients often increase their dose of opioid medications over time, which in turn increases their risk of overdose," said Julia Arnsten, professor at Albert Einstein College of Medicine.

Although less common, sleeping pills can lead to dependence, and can also cause grogginess the next day, interfering with people's work and social lives, she said.

As a consequence, some people have started taking marijuana to help with their symptoms, according to the study.