Marijuana fights Cancer - Study. Mounting evidence shows 'cannabinoids' in marijuana slow cancer growth. That's right, oil extracted from the marijuana plant has been shown to have extraordinary cancer-fighting properties.

Guillermo Velasco and colleagues at Complutense University in Spain have found that the active ingredient in marijuana, THC, causes brain cancer cells to undergo a process called autophagy.

Autophagy is the breakdown of a cell that occurs when the cell essentially self-digests.

The team discovered that THC had anticancer effects in mice with human brain cancer cells and people with brain tumors. When mice with the human brain cancer cells received the THC, the tumor growth shrank.