Cannabis smokers dating
In Britain, about eight million people admit to smoking cannabis, with at least one-third of youngsters claiming to have used it at some time.
They include Prince Harry, who admitted smoking the drug while a pupil at Eton.
The level of active ingredient in cannabis, tetrahydrocannabinol (THC) has increased from around 0.5 per cent 20 years ago to almost five per cent today.
THC affects the heart and blood vessels and many sudden deaths have been attributed to cannabis smoking.
Certain areas in the brain, such as the hippocampus, the cerebellum, the basal ganglia and the cerebral cortex, have a higher concentration of cannabinoid receptors.
The highest concentrations of THC are found in the dried flowers, or buds.
When marijuana smoke is inhaled, THC rapidly passes from the lungs into the bloodstream and is carried to the brain and other organs throughout the body.
He said: "Cannabis is as dangerous as cigarette smoking - in fact, it may be even worse - and downgrading its legal status has simply confused people.
"We have a clear public message about cigarette smoking.
Updated: More than 30,000 cannabis smokers could die every year, doctors warn today.