THUS, "DOPE":

Marijuana raises risk of cancer, other killer diseases (IANS, Nov 25, 2010)

Cannabis damages the immune system, leaving the body open to diseases from pneumonia to cancer, a research suggests.

In experiments, THC, the chemical behind the 'high' of cannabis fuelled the production of a flood of cells thought to weaken the body's inbuilt defences.

The finding suggests that cannabis, the drug of choice for many Britons, increases vulnerability to breast, bladder, lung and other tumours, as well as bacterial infections such as legionnaires disease, reports the European Journal of Immunology. [...]

While cannabis's links to devastating mental health problems are well known, its potential to wreck the immune system has received less attention.