The smoking habits of 119 subjects without silver/mercury dental fillings were compared to 115 subjects with amalgams. The amalgam group had 2.5-times more smokers per group than the non-amalgam group, which was highly significant. Because mercury decreases dopamine, serotonin, norepinephrine, and acetylcholine in the brain, and nicotine has just the opposite effect on these neurotransmitters, this may help explain why persons with dental amalgams smoke more than persons without amalgams.