SMOKING AND DEPRESSION perpetuate one another, study indicates Scientists have long observed a link between cigarette smoking and depression, and questions over which causes which–or whether both are caused by some third factor–have abounded. Now a study in adolescents has found that heavy smoking and depression affect each other reciprocally, creating a self-perpetuating pattern of unhealthy behavior and negative effect.

In their research, psychologist Michael Windle, PhD, and colleague Rebecca C. Windle, both of the University of Alabama at Birmingham, studied 1,218 high school students for one and a half years, beginning when the students were sophomores and juniors. Every six months, students completed questionnaires that assessed depression and cigarette smoking as well as variables such as temperament, parents’ smoking habits, social support within the family, delinquent activity, alcohol and other substance use, and friends’ alcohol and drug use.