The strongest predictor of successful smoking cessation is the degree of nicotine dependence, with heavier smokers finding it harder to quit.

A longitudinal study of British adults showed that the number of cigarettes smoked per day was the most significant predictor of quitting success, surpassing socio-demographic factors like social class or marital status. This finding underscores nicotine dependence's central role in cessation outcomes and suggests that strategies must address addiction intensity to be effective.