Researchers in Australia say evidence is weak as to whether medicinal cannabis treatments can help with mental illnesses such as anxiety, depression and psychosis. They add that doctors should be very careful when deciding to give the treatments to patients. The researchers examined scientific studies on the effects of medicinal cannabinoids on six mental health disorders. They found “a lack of evidence for their effectiveness.” Louisa Degenhardt is a drug and alcohol expert at Australia’s University of New South Wales in Sydney. She said her team’s findings have important effects for countries such as the United States, Australia, Britain and Canada. In those countries, doctors are making medical cannabis available for patients with some kinds of illnesses. The study results appeared in the publication The Lancet Psychiatry.