Season of birth bias in eating disorders—Fact or fiction?

Abstract

These findings suggest that SoB is a risk factor for AN. However, none of the studies have been methodologically satisfactory. Future research needs to overcome numerous methodological challenges and to explore specific hypotheses to explain this bias.

Season of birth bias and anorexia nervosa: Results from an international collaboration

“…As this is in accordance with our findings, it strengthens the conclusion that the proportion of shared variance between month of birth and AN probably fluctuates around 0.50%. How do the current findings compare with those of our earlier review 11 and the pooled meta-analysis 12 ? Total sample size used in the analyses can be found in the last row.…”

“…7 For females with AN, several studies report a season of birth bias with more births during the first 6 months of the year, 8 particularly in the spring months in Europe. 9,10 These findings are strengthened by a pooled meta-analyses of some of the UK samples 11 and a narrative review of the field. 12 In contrast, other studies do not support these findings, e.g., in Europe, [13][14][15][16][17][18] the USA, 19 Singapore, 20 or Australia.…”

Is season of birth related to disordered eating and personality in women with eating disorders?

“…We reduced uncertainty by determining birth date from the middle/end of the month (traditional season dates) and the beginning (insolation dates) diminishing the probability of miscalculation and focusing implications of results. This approach enabled a comparison of studies from distinct geographical locations using traditional seasons and an assessment of climatic variation using insolation criterion (23). Both appropriate, complementary techniques found no effect of seasonality.…”

“…Small sample sizes posed problems in previous studies [e.g., (23)], which may undermine statistical methods and power. By ignoring missing birth date data, most studies [e.g., (1, 2, 8)] did not account for exactness of birth dates.…”

“…Literature suggests more patients with AN restrictive subtype (RAN) are born in spring (23), thus we compared controls with women with RAN. We also compared controls with a larger sample with “any eating disorder” including AN and/or BN (Any ED).…”