The Chief Medical Officer for England has told MPs that there is not enough evidence to prove that medicinal cannabis products are safe.
Dame Sally Davies said that the law has “opened a Pandora’s box” with patients now believing cannabis can cure multiple illnesses.
She said that more work is needed to ensure the safety of drugs derived from the plant.
Dame Sally told the Health and Social Care Committee that until thorough drug trials have been completed, medicinal cannabis should only be prescribed as a “last resort”.
She said: “THC (Tetrahydrocannabinol) has an impact on the brain; it causes depression, schizophrenia, brain development problems in the young and adolescents.”
It comes as new NHS figures obtained by the Daily Mail reveal that mental disorders caused by cannabis use among nine to 18 year-olds have risen 38 per cent since 2014, and ten per cent in the last year.
Last week, a study in the Lancet Psychiatry journal revealed that potent forms of cannabis made users five times more likely to develop a psychotic disorder.
And the Head of NHS England, Simon Stevens, argued that legalising cannabis for recreational use would increase the rates of serious mental illness.