Many countries, including Canada, most US states, and Australia, allow the use of marijuana for medicinal purposes. Cannabinoids are employed to alleviate symptoms of certain diseases, including cancer. Medical marijuana is prescribed, for example, for chronic pain and spasms, nausea, and appetite improvement in AIDS patients. Cannabis can be smoked, using vaporizers, or consumed in the form of extracts and oral sprays.

Australia is conducting one of the world's largest long-term studies examining the impact of medical marijuana on the quality of life of patients with chronic illnesses. The Quality of Life Evaluation Study (QUEST) involves every chronically ill patient prescribed medical marijuana from November 2020 to December 2021.

Researchers analyzed the condition of 2,327 patients with chronic illnesses aged 18 to 97. The majority, 62.8%, were women. The most common conditions for which doctors prescribed medical marijuana were chronic pain (68.7%), insomnia (22.9%), anxiety disorders (21.5%), and depression (11%).

To alleviate symptoms, patients were prescribed various doses of medications containing phytocannabinoids – delta-9-tetrahydrocannabinol and cannabidiol, dissolved in carrier oil.

To assess the patients' condition, researchers used data from questionnaires and health and well-being forms that individuals filled out with their consent to participate in the QUEST project. The study was repeated every two weeks from the start of treatment, then monthly for three months.

Observations showed a statistically and clinically significant improvement in overall health-related quality of life and fatigue. Patients also reported a reduction in anxiety, depression, and pain.

To determine whether this improvement is long-lasting, researchers will now analyze observational data from a year of marijuana therapy. Additionally, the effectiveness of medical marijuana in treating sleep disorders requires further research, as scientists found no positive changes in the quality of nighttime rest.

Although the study did not consider the side effects of marijuana treatment, researchers noted that 30 participants dropped out of the study due to undesirable consequences.

Experts acknowledged that the study was funded by the medical marijuana producer Little Green Pharma, and patients received medications from this company. However, the report states that the sponsor did not participate in the study's design, data collection, analysis and interpretation, or report writing. The study was conducted by independent experts, and all authors are responsible for the integrity of the data and the accuracy of their analysis.