The amount of alcohol people drink influences their health. How often people drink alcohol and the amount they drink depends on genes and other biological factors, as well as social factors, such as the drinking behaviors of one's contacts. These social factors are in part why parents often worry when their children have friends who use alcohol. It is also why some alcohol treatment programs advise people with alcohol problems to avoid settings that typically invite drinking. Recent research has shown how other health issues associated with behavior (such as smoking, obesity, and sexually transmitted diseases) travel in social networks.