
Smoking in the first 30 minutes after waking nearly doubled the, already high, risk of lung cancer.
Cancer Research UK suggested people who were quick to smoke may inhale more smoke into the lungs.
Scientists at the Penn State College of Medicine in the US looked at 4,776 smokers with lung cancer and 2,835 smokers without cancer.

Cancer Research UK's Professor Robert West said: "Smokers who light up soon after waking tend to smoke each cigarette more intensively.