Many people will tell you that smoking cannabis (aka marijunana, the world’s most famous ‘pot plant’) is bad for you. Another reason to avoid the hallucinogenic plant is provided by work of an international team of immunologists who have discovered that marijuana may trigger a suppression of the body’s immune functions. Working with mice, Venkatesh Hegde et al. (European Journal of Immunology 40: 3358–3371, 2010) found that injected cannabinoids – including the best-known one, THC (delta-9 tetrahydrocannabinol) – can trigger a massive number of myeloid-derived suppressor cells (MDSCs). MDSCs, which actively suppress the immune system, increase in cancer patients and it is believed that they may suppress the immune system against cancer therapy, actually promoting cancer growth. So, although THC may bring pain relief in some medical applications, it could immuno-compromise in other instances with attendant cancer risk. Please remind Frank to say ‘No, thank you’ to drugs!