An anonymous reader writes: Women tend to find it harder to quit smoking than men, and a new study suggests why — women's brains respond differently to nicotine, the researchers say. When a person smokes, the number of nicotine receptors in the brain — which bind to nicotine and reinforce the habit of smoking — are thought to increase in number. The study found in men, this is true — male smokers had a greater number of nicotine receptors compared to male nonsmokers. But surprisingly, women smokers had about the same number of nicotine receptors as nonsmokers. "When you look at it by gender, you see this big difference," said study researcher Kelly Cosgrove, an assistant professor of psychiatry at Yale University School of Medicine.