Objectives To compare the odds of depression in obese and overweight children with that in normal-weight children in the community.

Design Systematic review and random-effect meta-analysis of observational studies.

Data sources EMBASE, PubMed and PsychINFO electronic databases, published between January 2000 and January 2017.

Eligibility criteria for selecting studies Cross-sectional or longitudinal observational studies that recruited children (aged <18 years) drawn from the community who had their weight status classified by body mass index, using age-adjusted and sex-adjusted reference charts or the International Obesity Task Force age-sex specific cut-offs, and concurrent or prospective odds of depression were measured.

Results Twenty-two studies representing 143 603 children were included in the meta-analysis. Prevalence of depression among obese children was 10.4%. Compared with normal-weight children, odds of depression were 1.32 higher (95% CI 1.17 to 1.50) in obese children. Among obese female children, odds of depression were 1.44 (95% CI 1.20 to 1.72) higher compared with that of normal-weight female children. No association was found between overweight children and depression (OR 1.04, 95% CI 0.95 to 1.14) or among obese or overweight male subgroups and depression (OR 1.14, 95% CI 0.93 to 1.41% and 1.08, 95% CI 0.85 to 1.37, respectively). Subgroup analysis of cross-sectional and longitudinal studies separately revealed childhood obesity was associated with both concurrent (OR 1.26, 95% CI 1.09 to 1.45) and prospective odds (OR 1.51, 95% CI 1.21 to 1.88) of depression.

Conclusion We found strong evidence that obese female children have a significantly higher odds of depression compared with normal-weight female children, and this risk persists into adulthood. Clinicians should consider screening obese female children for symptoms of depression.

Background Childhood mental illness is poorly recognised by healthcare providers and parents, despite half of all lifetime cases of diagnosable mental illness beginning by the age of 14 years.¹ Globally, depression is the leading cause of disease burden, as measured by disability-adjusted life years, in children aged 10–19 years.² Untreated, it is associated with poor school performance and social functioning, substance misuse, recurring depression in adulthood and increased suicide risk, which is the second leading cause of preventable death among young people.^3–6 The resulting cost to the National Health Service of treating depression is estimated at over £2 billion, and the wider social and economic impact of depression is likely to be considerable.⁷