cigarettes risk_factor_for lung cancer

number of cigarettes smoked ... are reinforced by significant positive correlation with lung cancer (rg = 0.39, P= 6.35 × 10−10)

cigarette smoking is a well-established risk factor of large effect size, not all smokers develop lung cancer.

lung cancer risk has been shown to steadily increase up to 20-30 cigarettes per day

ORs of lung cancer risk ... increase with increasing intensity of smoking only for subjects who smoke up to 20 cigarettes per day

cigarette smoking being neither necessary nor sufficient to cause lung cancer

smoking ... contributes to over 5 million deaths ... including an estimated 82% of lung cancer deaths