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

Month of birth and mental disorders: A population-based study and validation using global meta-analysis

OBJECTIVE

Month of birth (MOB) is associated with specified mental disorders (MDs). However, whether these relationships extend to all MDs remains unclear. We investigate the association using a population-based cohort study and a meta-analysis.

METHODS

First, we examined patients with 34 DSM-5-classified MDs in the Taiwan national database. We estimated the relative risk ratios (RR) of each illness in each MOB relative to that in the general population and assessed the periodicity, with six further sensitivity analyses. Second, we searched PubMed, Embase, and Cochrane for related articles through 31 December 2020. We used a random-effects model, pooled RRs with 95% confidence intervals of each MOB from the identified studies, and transformed them from MOB to relative age in a year or season.

RESULTS

The cohort included 1,951,777 patients. Except for posttraumatic stress disorder, dissociative disorders, feeding/eating disorders, gender dysphoria, and paraphilic disorders, the other MDs had significant MOB periodicity. The meta-analysis included 51 studies investigating 10 MDs. The youngest age at the start of school owing to MOB was associated with the highest RRs of intellectual disability (1.13), autism (1.05), attention-deficit/hyperactivity disorder (1.13). Winter births had significant risks of schizophrenia (1.04), bipolar I disorder (1.02), and major depressive disorder (1.01), and autumn births had a significant risk of alcohol use disorder (1.02). No significant associations between season of birth and Alzheimer's disease, or eating disorders were found.

CONCLUSIONS

MOB is related to the risks of certain MDs. This finding provides a reference for future research on the etiology of MDs.

Childhood risk factors for lifetime bulimic or compulsive eating by age 30 years in a British national birth cohort

OBJECTIVE

To examine whether previously identified childhood risk factors for bulimia or compulsive eating (BCE) predict self-reported lifetime BCE by age 30 years in a prospective birth cohort.

METHOD

Using data from the 1970 British Cohort Study at birth, 5, and 10 years, associations between 22 putative childhood risk factors and self-reported lifetime BCE at 30 years were examined, adjusting for sex and socioeconomic status.

RESULTS

Only female sex (odds ratio (OR): 9.2; 95% confidence interval (CI): 1.9-43.7; p = 0.005), low self-esteem (OR:2.9; 95%CI: 1.1-7.5; p = 0.03) and high maternal education (OR:5.4; 95%CI: 2.0-14.8; p = 0.001) were significantly associated with higher risk of BCE, whereas high SES at 10 years was significantly protective (OR:0.2; 95%CI: 0.1-0.8; p = 0.022) of BCE in fully adjusted multivariable logistic regression analysis.

DISCUSSION

Our findings do not support a strong role for childhood weight status and eating behaviours in the development of bulimia and compulsive eating pathology, rather suggesting a focus on self esteem may have greater relative importance. Findings in relation to maternal education and SES need further exploration.

Prenatal and perinatal factors in eating disorders: a descriptive review

OBJECTIVE

The objective of this descriptive review is to summarize the current scientific evidence on various prenatal and perinatal exposures affecting later development of eating disorders among offspring.

METHOD

Studies were searched from PubMed database with the following keywords: eating disorders and disordered eating and anorexia nervosa and bulimia nervosa and binge eating disorder and prenatal exposure delayed effects and maternal exposure and perinatology. A comprehensive manual search, including search from the reference list of included articles, was also performed.

RESULTS

The attributable risk for prenatal and perinatal factors in anorexia nervosa (AN) is 3.6%. Numerous prenatal and perinatal factors have been associated with offspring AN, but only prematurity has been replicated in different samples. The risk of bulimia nervosa (BN) in offspring has attracted less study, and despite varying positive associations, there are no replicated findings. Higher prenatal testosterone may protect against the development of a range of disordered eating symptoms, although studies are not consistent.

DISCUSSION

Evidence in support of an effect of prenatal and perinatal factors on eating disorders or disordered eating in offspring is conflicting. If present, the overall effect appears to be relatively small, and it is likely that the early risk factors operate in conjunction with other biological, genetic, and/or environmental risk factors to bring on eating pathology. Genetically sensitive designs, such as sibling and twin studies, are needed to disentangle the different types of risk factors and ensure that prenatal/perinatal effects are "causal" rather than indications of genetic risk.

Lack of pattern of birth in patients with bulimia nervosa

OBJECTIVE

An excess of bulimia nervosa (BN) births during the fall has been recently reported, but this finding has not been yet adequately replicated. The purpose of our study was to evaluate the presence of a seasonal birth pattern in a representative clinical sample of women with BN.

METHOD

We registered the month of birth of 216 female patients who fulfilled all the criteria for BN according to DSM-IV on admission to a specialized eating disorders service in Spain.

RESULTS

Our analyses showed no significant variation in the season of birth of our BN sample when compared to a general population.

DISCUSSION

Our data do not support the hypothesis of a season of birth bias in BN.