Smoking cannabis may suppress the immune system and increase cancer risks, new research suggests.
The drug triggers the production of cells that weaken the body's resistance to cancer, scientists believe.
A US study found that active compounds in cannabis activated biological pathways to generate "massive numbers" of the cells, known as myeloid-derived suppressor cells (MDSCs).
MDSCs are special cells that act as a safety brake on the immune system. Cancer patients are known to have increased numbers of MDSCs.
Lead researcher Dr Prakash Nagarkatti said: "These results raise questions on whether increased susceptibility to certain types of cancers or infections caused from smoking marijuana results from induction of MDSCs."