Objectives: To determine the prevalence of learning disorders, defined as repeating a year, in adolescents and associated social and health risk factors., Patients and Methods: A prospective cross-sectional study of a cohort of 14-year-olds was performed. Data (medical, social and family history and anthropometric data) were collected by pediatricians and a self-administered questionnaire on school progress, health-related self-image, physical activity, leisure-time activities, family and social relationships, drug and alcohol consumption, and self-esteem was given to the adolescents., Results: Of 287 adolescents, three were excluded because of mental deficiency. Of the 284 adolescents included in the study (135 girls and 149 boys), 48 (16.9 %) had learning disorders. No significant differences were found between sexes (18.1 % in boys vs. 15.55 % in girls). Learning disorders increased with the number of siblings (p 0.003). The prevalence was greater in the lower social classes (classes I, II, III: 6 %; class IV: 15.9 %; class V: 33 %; p 0.019) and in families with psychosocial risk factors (48.4 % vs. 12.7 %; p > 0.0001). Adolescents with learning disorders participated less in sports (50 % vs. 60.6 %; p 0.03), read less frequently (8.3 % vs. 27.1 %; p 0.005) and watched more TV on working days (2.4 hours/day vs. 1.6 hours/day; p 0.033). Girls with learning disorders were less aware of contraceptive methods (71.4 % vs. 95.6 %; p 0.0002) and of sexually transmitted diseases (71.4 % vs. 93 %; p 0.003). Adolescents with learning disorders started smoking earlier (39.6 % vs. 20.8 %, p 0.0053) but no differences were found in regular smoking., Conclusions: Learning disorders constitute a common problem requiring pediatric care due to their influence on adolescents' overall health and their relationship with risk factors such as lower awareness of birth control and sexually transmitted diseases, greater sedentariness, and earlier initiation of smoking. more...