Could the time of year at which you were born predict your future risk of mental illness? Some researchers think so. Though study results have been mixed, researchers from around the world have found that birth season could be an important predictive factor in the development of adult mood disorders, schizophrenia, and anorexia.
Why? Because the time of year at which you’re born can influence neurotransmitters in your brain, at birth and beyond. Researchers also believe that seasonal factors can affect your development in the womb — the time of year during which your mother carried you could influence such factors as her diet, her level of sunshine exposure, or whether she developed a cold or flu.
The Birth Season-Mood Disorder Link
According to a study from Budapest’s Semmelweis University, babies born in the spring grow to develop happy, optimistic temperaments, while babies born in the summer are prone to moodiness and even bipolar disorder. Winter babies were found to be the least irritable as adults, while fall babies were least likely to develop depressive disorders.
For the study, researchers asked 366 university students to fill out surveys regarding their temperaments and personalities. The researchers believed that variations in personality, temperament, and risk of mental illness among people born at different times of the year may go back to the Hungarian diet, which changes seasonally. Traditional Hungarian winter foods, for example, like sweet potato cottage pie or veal stew, contain a lot of tryptophan, an amino acid that is crucial for the production of serotonin.
One flaw of studies of this type is that diet and other lifestyle factors can vary widely from one country to the next. The seasonal patterns that help shape lifetime mental illness risk for Hungarian babies may not be present for babies of other nations. For example, a much larger British study examined 58,000 people with mental disorders and 29 million people from the general English population. This study’s findings were very different, in some ways, from those of the Hungarian study.
While the British study did confirm that babies born in the autumn seem least prone to depressive disorders later in life, the study also found that winter and spring babies were most prone to schizophrenia, bipolar disorder, and depressive disorders — the opposite of what the Hungarian study found. January babies were found to be at the highest risk of growing up to need medications like Seroquel to treat the symptoms of schizophrenia or bipolar disorder, while babies born from July through September had the lowest risk of these disorders. While the Hungarian study found that spring babies were least likely to later suffer depression, the British study found that babies born in May were most likely to one day need drugs like Abilify to treat depression.
The British researchers believe that seasonal factors like exposure to sunlight — which is minimal during the winter months — or cold and flu infection could influence the future mental health of babies still in their mothers’ wombs. Some researchers have also pointed out that the key factors here may not even be prenatal. Children born in winter and spring may be smaller, younger, or less mature than their classmates, and may suffer years of childhood stress linked to struggling socially or academically. This prolonged stress could easily lead to mental illness in adulthood.
Babies Born in Spring More Prone to Anorexia
Schizophrenia and mood disorders aren’t the only mental illnesses influenced by birth season. An Oxford University study found that babies born between the months of March and June are most likely to suffer anorexia as adults. People born in September and October were least likely to later develop anorexia.
The study examined the birth dates of 1,293 anorexia patients with those of people not in anorexia treatment. Again, researchers believe that seasonal factors mothers face during pregnancy, like exposure to sunlight, infection, nutrition or even changes in temperature as winter moves into spring could be behind the unusually high number of anorexia patients with spring birthdays.
Further research will be needed for scientists to fully understand the link between season of birth and adult risk of mental disorders — if there is one. A range of prenatal and even postnatal factors could influence the adult mental health of babies born at different times of the year. Winter and spring babies, for example, could experience higher rates of adult mental illness thanks to their mothers’ diets, lack of sun exposure, or exposure to cold and flu — or it could be due to another set of factors entirely. Just because you were born at a particular time of the year doesn’t mean you’re guaranteed to develop, or not to develop, a specific mental illness — researchers are only beginning to untangle the many mysterious factors that go into upsetting a person’s mental and emotional equilibrium.