The month of your birth predicts your future in surprising ways, not through astrology, but instead from neuroscience. What does this research predict for the future of a baby born in July?
According to a recent study, children born from June through August, performed worse on achievement tests later in school, and were more frequently diagnosed with Specific Learning Difficulties.
The overall impact on children of their month of birth on their schooling results, was described by the Educational Psychologists' team conducting the research, led by Professor Roy Martin of the University of Georgia, USA, as 'enormous'.
Adults suffering a variety of psychological and neurological problems demonstrate date of birth patterns differing from the general population.
Referred to as 'season-of-birth' research, more than 100 studies in the northern hemisphere have found those with schizophrenia and related psychoses (severe psychiatric disorders associated with hearing voices and delusions) are born in higher numbers than expected, in winter or early spring.
Birth date effects have been found for many other conditions, for example some research has found those with autism appear more likely to be born in August ('Month of conception and risk of autism', Epidemiology), while another study found male alcoholics more likely to be born between March and July ('Season of Birth comparison of patients with schizophrenia, affective disorders and alcoholism', Acta Psychiatrica Scandinavica).
During winter upper respiratory infections, particularly pneumonia and influenza, reach peak rates between the beginning of December and early March. Such infections might affect the developing brain of the foetus. December through mid-March birth dates, interestingly, are also the highest risk for later developing schizophrenia as an adult. That the uterine environment can still have effects decades later, is one of the most intriguing findings in neuroscience.
Another theory which explains this season of birth effect for schizophrenia and related psychoses is the reduced availability of sufficient ultraviolet light absorbed through maternal skin, and needed to produce vitamin D. This might play a critical role in brain development during the foetal period.
This vitamin D theory would predict the season of birth effect will get stronger the further north you go as the available sunlight decreases in higher latitudes. This was found when pooling data in eight season of birth studies for schizophrenia, in the Northern Hemisphere ('Season of birth effect and latitude: A systematic review and meta-analysis of Northern hemisphere schizophrenia studies', Schizophrenia Research).
Roy Martin, Patricia Foels, Greg Clanton and Kathryn Moon review the research in this area in their paper entitled 'Season of Birth Is Related to Child Retention Rates, Achievement, and Rate of Diagnosis of Specific LD' (LD = Learning Disability), citing a study which found that Learning Difficulties for summer-born boys was seven times the rate for autumn- and winter-born boys.
However, there are other theories other than neurological ones for this finding, Martin and colleagues concede in their paper published in the Journal of Learning Disabilities. For example, schools often have a cut-off birth date for entrance which is often in the fall, for example September 1st.
Children whose birth dates fall in the months just prior to the cut-off date, therefore, are the youngest in their grade, Martin and colleagues point out. Thus, the preceding findings might be down to differences in maturity, as reflected by relative age in a given classroom. Do teachers, psychologists and doctors mistake maturity for ability? Many children with learning difficulties are the youngest in their class.
A study of 1,136 boys at a private school in England, cited by Martin and colleagues, found that by the fourth year of school, autumn born children (the oldest in their year) tended to be in the top "stream," whereas summer-born children (the youngest in their year) tended to be in the bottom.
But besides the intra-uterine stress theory there is a 'self-concept hypothesis' that might explain some of these season of birth effects.
Martin and colleagues point out the youngest children in a class may be at a disadvantage to others in the same year with regard to stature, strength, motor, social skills and intellectual maturity. The cumulative effect of all these relative shortcomings might be lowered self-esteem, resulting in worse engagement with school and therefore poorer achievement.
So what is the very best month to be born in? It seems at first glance that each month has its advantages and disadvantages.
For example, a recent study found those born in September were less likely to suffer pollen allergy - it might be that being born at the end of the pollen season protects from this allergy ('The association of month of birth with atopy in adult patients with asthma and rhinitis in Anatolia, Turkey', Allergologia et Immunopathologia), but another recent study found coeliac disease patients were more likely to be born in spring ('Multicenter Study on Season of Birth and Celiac Disease: Evidence for a New Theoretical Model of Pathogenesis', The Journal of Pediatrics), and the authors of that study link the finding with UV light exposure during pregnancy.
Another recent study found those born in Europe from October-December lived longer than those born April-June, whereas the pattern in Australia (or the Southern Hemisphere) was a mirror image reversal, with the greatest life expectancy for those born in April-June. ('Lifespan depends on month of birth', Proceedings of the National Academy of Sciences).
You might consider that being born a royal means you are born lucky - are some people indeed born lucky?
Psychologists Jayanti Chotai, of Umea University in Sweden and Richard Wiseman from the University of Hertfordshire, investigated this question in 22,372 subjects born in the United Kingdom. The results were published in a paper entitled 'Born lucky? The relationship between feeling lucky and month of birth' in the academic journal Personality and Individual Differences.
Level of agreement was measured for the statement, "In general, I am a lucky person, that is, I tend to experience lucky breaks and be in the right place at the right time." Winter born agreed much less with the luck statement than summer born. The lowest agreement with feeling lucky was for the birth month November, and maximum agreement for birthdays in May.
The luckiest people alive - or at least people who believe they are lucky - are born in May.
The Royal baby, it appears, has missed out being born in May by around two months - how unlucky is that?