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

Abstract

We assessed the relation between season of birth and eating disorder symptoms and personality characteristics in a sample of 880 women with eating disorders and 580 controls from two Price Foundation Studies. Eating disorder symptoms were assessed using Structured Interview of Anorexic and Bulimic Disorders and the Structured Clinical Interview for DSM-IV. Personality traits were assessed using the Temperament and Character Inventory and the Frost Multidimensional Perfectionism Scale. Date of birth was obtained from a sociodemographic questionnaire. No significant differences were observed 1) in season of birth across eating disorder subtypes and controls; nor 2) for any clinical or personality variables and season of birth. We found no evidence of season of birth variation in eating disorders symptoms or personality traits. Contributing to previous conflicting findings, the present results do not support a season of birth hypothesis for eating disorders.

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

“…Our findings and conclusion are in accordance with those of Crisp, 15 Button and Aldridge, 16 Favaro et al, 17 and Shuman et al 19 However, assuming that the power calculations for harmonic analysis may indeed generalize to other harmonic tests, 40 the possibilities of type II errors are present for most of the findings in the previously published studies. In addition, this implies that the significant findings of Nielsen 9 and Rezaul et al 10 might be Type I errors.…”

“…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.…”

Season of Birth Bias and Bulimia Nervosa—Results from a Multi‐centre Collaboration

“…One study found a statistically significant autumn peak in the USA (Brewerton et al, ), whereas another found significant spring peaks in the UK in two out of four sub‐analyses (Morgan & Lacey, ). Two other studies, one based in the UK and the other originating from the Price Foundation Studies, did not report significant findings (Button & Aldridge, ; Shuman et al, ).…”

“…Statistically significant findings of a season of birth bias for women with bulimia nervosa have been explained by (i) annually fluctuating patterns in parental sexual activity and/or the fertility of parents of probands, (ii) altered foetal development due to environmental temperatures, sunlight exposure, maternal infections or nutritional changes at conception, gestation or early development, and (iii) other factors such as relative age effect, selection bias, misdiagnoses or unrepresentativeness of the samples (Brewerton et al, ; Morgan & Lacey, ). Lack of statistically significant findings of a season of birth bias for women with bulimia nervosa has been explained by (i) small sample sizes, (ii) poorly selected control groups and (iii) that there is no season of birth bias in bulimia nervosa (Button & Aldridge, ; Shuman et al, ).…”

“…The previous studies exploring season of birth bias for people with bulimia nervosa (Brewerton et al, ; Button & Aldridge, ; Morgan & Lacey, ; Shuman et al, ) have some methodological shortcomings, most importantly the lack of reports of, or comments on, power calculations and effect sizes. The American Psychological Association Publication Manual 6th edition and several journals encourage authors to include the observed effect sizes, even for non‐significant findings, as they are more informative than p ‐values and provide valuable information for future studies and meta‐analyses (American Psychological Association, ; Ellis, ).…”