Hypnosis is the most effective way of giving up smoking, according to the largest ever scientific comparison of ways of breaking the habit. Results of more than 600 studies of 72,000 people from America and Europe compared various methods of quitting. On average, hypnosis was over three times as effective as nicotine replacement methods and 15 times as effective as trying to quit alone.

Reported in New Scientist and University of Iowa, Journal of Applied Psychology

Effects of stopping smoking on the body:

20 minutes - Blood pressure and heart rate returns to normal.

12 hours - Carbon monoxide levels drop back to normal.

24 hour - The body starts to clear out the mucus build-up in the lungs.

72 hours - Breathing becomes easier and energy levels increase.

1 month - Appearance of skin improves.

3 to 9 months - Lung function can improve by up to 10 per cent.

1 year - Risk of suffering from a heart attack falls to about half of that of a smoker.

10 years - Risk of developing lung cancer falls to about half of that of a smoker.

15 years - Risk of suffering heart attack falls to that of a non-smoker.