Kivonat:
Introduction: Smoking habits are influenced by environmental (family, friends) and psychologic factors. Aim: To investigate environmental factors which influence the smoking habits of monozygotic and dizygotic twins. Method: 45 monozygotic and 23 dizygotic twin pairs (age 35+/-16 years) completed a questionnaire. Results: Maternal non-smoking decreases the risk of smoking of the twin children by 53%, while this effect accounts for 49% by the father. Dizygotic twins are more influenced by parents (70%) than monozygotics (31-36%). If the twin or non-twin sibling does not smoke, the risk that the twin individual starts smoking, is decreased by 86% both in monozygotic and dizygotic twins. If an individual smoking is present in the fraternity and he or she does not attempt to quit, the risk of smoking increases 8.3-fold. The role of fraternity is more important in males and youth. Conclusions: The parents' and the siblings' exemplary behaviour helps to avoid smoking initiation of young twins. Orv. Hetil., 2013, 154, 978-984.