This review was conducted to evaluate the influence of the birth season on the occurrence of anorexia nervosa. The review of previous studies on the incidence and occurrence patterns of anorexia nervosa helped with a comparative analysis in the current study. It was seen that there were more births of anorexic patients during the months of March and June and very few births of anorexic patients were reported from September to October. Hence, anorexia nervosa shows seasonal variation, requiring further studies to identify the cause.
Many disorders, especially neurological ones could be closely associated with the season of the birth date of the baby. This pattern has been studied in various psychiatric disorders, such as schizophrenia, bipolar disorder, major depression and suicidal behavior. A similar pattern could be recognized in eating disorders, such as anorexia nervosa too. However, previous studies on anorexia were found to be inappropriate due to smaller study groups or the type of statistical methods used to analyze the data. Anorexia nervosa is characterized by an inhibition to eat healthy due to fear of gaining weight and it is more commonly found in females. A review of the previous studies helped to increase the study population and incorporate better methods of statistical analysis to evaluate the data in the current study. The previous studies used simple statistical methodologies leading to inconclusive results. More intricate methods were utilized in this review of the previous anorexia nervosa studies.
* Medical databases were searched for articles with terms including anorexia nervosa, season, birth and month.
* Overall, 1,293 anorexia nervosa births were identified and compared with the general population born between 1950 and 1980.
* With the method used to analyze the data, fluctuations of incidence within each year could be identified.
* This factor gave it an edge over the statistical methods used in the previous studies.
* The births in the anorexia nervosa group seemed to vary with the month of birth and were significantly different from the births in the general population group.
* The incidence of births of the anorexic patients was higher in the early months of the year.
* There were more births of anorexic patients between the months of March and June and the least between September and October.
Further studies must be conducted with larger study groups as a seasonal pattern of disease incidence is shown in this study. Also, study groups involving different populations at different latitudes would help to confirm the findings of this study. “Identification of the relevant seasonal risk factors will undoubtedly be important for future disease prevention strategies.”
This study involved the largest population of anorexic patients to date and this disorder was found to have a seasonal incidence at birth. More of these patients were born during spring and very few during the fall season. As with most neurological disorders, the season-of-birth effect applies to anorexia nervosa also. This also fits the fetal origin of adult disease hypothesis, suggesting an exposure to environmental factors during spring or the absence of an essential factor at the same time, resulting in the disease. Temperature changes, vitamin D levels, exposure to sunlight, maternal nutrition and certain infections could be a few factors influencing the disease. However, the exact cause is still unknown. Identification of these factors could help in formulating disease prevention strategies.
For More Information:
Season of Birth and Anorexia Nervosa
Publication Journal: The British Journal of Psychiatry, March 2011
By Giulio Disanto, MD; Adam Handel, BMBCh; University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom