BAKERSFIELD, Calif. -- New research has found that tiny genetic differences may have a big effect on smoking habits.

Doctors from the University of Michigan studied 435 people -- some who had tried smoking but never got hooked, and others who smoked an average of at least five cigarettes per day.

They found a single mutation in a gene that helps process nicotine increased the odds that a person would keep smoking.

The protective form of the gene is not common in the population, but scientists found it occurred frequently in non-smokers. The unfavorable mutation may even cause a "mild high" from smoking.

Regular smokers were much more likely to have the mutation and also eight times more likely to have experienced a pleasurable buzz from their first cigarette.

Previous research has linked the same gene to an increased risk for lung cancer.