Pattern of birth in early-onset anorexia nervosa: an equatorial study

Abstract

This lack of seasonal variation in the equator adds support to the "temperature at conception" hypothesis.

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

“…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. 21 There are two main explanations posed for any season of birth bias for AN: (i) altered neuropsychological functioning due to maternal infections during pregnancy, nutritional changes or sunlight exposure during gestation or the post partum period, [8][9][10]17,18 and (ii) altered parental fertility or reproductive patterns due to cultural influences, cyclothymia, or due to disordered eating patterns in the mothers which in combination with environmental temperature may influence fertility patterns.…”

“…21 There are two main explanations posed for any season of birth bias for AN: (i) altered neuropsychological functioning due to maternal infections during pregnancy, nutritional changes or sunlight exposure during gestation or the post partum period, [8][9][10]17,18 and (ii) altered parental fertility or reproductive patterns due to cultural influences, cyclothymia, or due to disordered eating patterns in the mothers which in combination with environmental temperature may influence fertility patterns. 9,10,13 There are three explanations for the contradictory findings of no season of birth bias: (i) low statistical power, 8 (ii) geographical differences in the bias, 20 and (iii) that there may indeed not be any bias. 18,21 Methodological limitations associated with the previously published studies includes: (i) absence of any a priori test-specific power calculations, thereby increasing the risk of both Type I and II errors, (ii) multiple subanalyses, which sometimes do not include a control group consisting of the general population.…”

Season of birth and eating disorders: Patterns across diagnoses in a specialized eating disorders service

“…7 The findings are, however, inconsistent and there is evidence to suggest that any seasonal effect for anorexia nervosa may not apply to those born in warmer climates. 8,9 In the case of the other eating disorders, there is relatively little evidence. Morgan and Lacey reported on 935 patients with bulimia nervosa at St. George's Hospital, London.…”

Absence of seasonal pattern of birth in patients with anorexia nervosa

“…[7][8][9][10][11] Those studies that have observed a season of birth bias share methodological problems like definitions of seasons, accuracy of diagnosis, sample sizes, and comparison groups. We found no evidence of seasonal variation in date of birth for patients with the restricting subtype either.…”

“…A recent meta-analysis 1 concluded that there is a consistent season of birth bias for anorexia nervosa (AN) births in the United Kingdom (UK). [7][8][9] In view of these inconsistent findings and given the shortage of studies in our hemisphere outside the UK, our aim was to investigate whether there is a seasonal variation in month of birth in a representative sample of patients with AN born in a warmer climate. Some of these studies [1][2][3][4][5][6]12 suggest that more patients with AN than expected are born during the spring months, especially patients with the restricting subtype of AN.…”