(DAILY MAIL) -- Men who smoke too much marijuana could face fertility problems because the drug makes sperm 'mellow' causing it to 'swim in circles'.

Cannabis - which is the most widely-used illegal drug in Britain - tends to leave users feeling chilled out and relaxed.

But now researchers have revealed that it has the same effect on sperm and regular weed smoking can cut counts of the cells by as much as a third.

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