What explains differences in smoking, drinking, and other health-related behaviors

"We explore economic model of health behaviors. While the standard economic model of health as an investment is generally supported empirically, the ability of this model to explain heterogeneity across individuals is extremely limited. Most prominently, the correlation of different health behaviors across people is virtually zero, suggest that standard factors such as variation in discount rates or the value of life are not the drivers of behavior. We focus instead on two other factors: genetics; and behavioral-specific situational factors. The first factor is empirically important, and we suspect the second is as well"--National Bureau of Economic Research web site.