Introduction and aims: Familial aggregation of low back pain (LBP) symptoms has been described. However, this may be due to genetic factors or common exposure to environmental factors. This study evaluated the relative contribution of genetic and environmental factors to childhood LBP.

Methods: Data was collected from 1995 to 1998 from a national sample of 1790 Finnish twins aged 11-years. A validated pain questionnaire was used to assess LBP pain. Information was also collected on children’s perception of parent-child relationships, parenting behaviours and home environment. In addition, children were asked about various sedentary and active life-style activities. Variance components for genetic and environmental factors were estimated by using biometric structural equation modelling techniques.

Results: The prevalence of LBP at least once a month was 15.7%, and at least once a week was 6.7%. There was small difference in pairwise similarity of LBP between monozygotic and dizygotic pairs, suggesting little genetic influence. LBP was not associated with either sedentary or active lifestyle activities, but was strongly associated with children’s unsatisfactory perception of the following: home environment (p< 0.001), parenting behaviours (Spearman rho = 0.12, 95% CI 0.06–0.18), relationship with mother (p=0.02) and father (p=0.04). Of the total variance in LBP, 41% (95% CI 34 to 48) could be attributed to shared environmental factors within families; and 59% (52 to 66) to unshared environmental factors.

Conclusion: Genetic factors seem to play a very minor role in LBP in 11-year-old twins. Rather than being related to various aspects of lifestyle activities, childhood LBP is best predicted by children’s perception of home environment and family functioning.