Researchers from the United Kingdom analyzed results of a survey of more than 5,000 young people ages 10 to 15. They used a variety of indicators to rate how healthy a lifestyle each person led, using factors like eating and drinking habits, smoking and drug use, and participation in sports and other activities. In addition, they used responses to several questions to rate each person on his or her level of happiness. They found that healthier habits were strongly related to how happy these young adolescents reported themselves to be.