Cannabinoids such as the main active component of marijuana have anticancer effects on human brain cancer cells, a new study has found. Guillermo Velasco and colleagues at Complutense University, Spain, found that THC induced the death of various human brain cancer cell lines and primary cultured human brain cancer cells by a process known as autophagy. Administration of THC to mice with human tumours decreased tumour growth and induced the tumour cells to undergo autophagy.