Can Your Birthday Predict Your Mental Health?

Research reveals some unnerving links, and suggests some explanations.

Posted Oct 06, 2015

Stone36/Shutterstock
Source: Stone36/Shutterstock

For most of us, horoscopes are fun little time wasters or goofy conversation starters.

On a Sunday morning, you may look at the newspaper or check the Internet to read your horoscope for the day. It may claim that good luck is in your future, although you should be careful not to overestimate your abilities, especially when it comes to that new project at work. You may believe this is all consistent with your Aries personality, since people with this sign tend to have high expectations of their own abilities. . .

Of course, researchers have long been aware that horoscopes don’t actually correlate with behavior—in a key 1985 study published in the prestigious journal Nature, scientists found that predictions based on astrology were no better than chance.

Despite having debunked the myth of astrology, however, scientists have found that a person’s future health can be linked to his or her birthday. The month in which people are born can influence their future, from their longevity to their profession.

Mental illness linked to birth month

In a 2012 study, a group of researchers at Queen Mary University in London investigated whether the risk of schizophrenia, bipolar disorder, and major depression increased depending on one's birth month. These researchers looked at more than 29 million people from England’s general population, 58,000 of whom were diagnosed with one of these three conditions.

Winter babies were at the greatest risk for schizophrenia and bipolar disorder, with January being the most common birth month for this group. Spring babies, meanwhile, appeared to be at greatest risk for depression, which demonstrated an almost significant peak in May.

Schizophrenia had significant lows for people born in July, and bipolar disorder had significant lows for individuals born in August and September. People born in November were significantly less likely to experience depression.

Suicide linked to birth month

According to the National Alliance on Mental Illness (NAMI), an estimated 90 percent of individuals who commit suicide suffer from mental illness. It should come as no surprise, then, that suicidal behavior may also be linked to birth month. Another British research team examined the data from nearly 27,000 suicides between 1970 and 2001 and found that individuals born in April, May, and June had the greatest risk of committing suicide. Their risk was 17 percent higher than that of people whose birthdays fell in the autumn or winter.

Why does season matter?

Scientists aren’t quite sure why some birth months are linked to greater incidences of mental health disorders than others, although there are a few possibilities.

One possibility is that birth month influences our biological clock. In a 2010 study, scientists found that mice born in the winter were less able to adapt to a summer light cycle than mice born in other seasons. Our ability to regulate our biological clock is strongly linked to mood. The researchers speculated that difficulties with these biological rhythms could increase the risk of mental health disorders in humans born in the winter.

Another possible candidate is vitamin D. Vitamin D is produced when our bodies are exposed to sunlight, and many people are aware that a lack of the vitamin can weaken bones and cause rickets, but recent research has uncovered another role for the vitamin in the nervous system: Lower levels of vitamin D could feasibly impact the developing brain, potentially explaining higher rates of mental illnesses for people born in the cold winter or the wet spring. One Danish study found that individuals with the lowest levels of vitamin D at birth were more likely than others to develop schizophrenia later in life.

Infections may be at least partially to blame. During the winter, a mother may be more likely to have the flu. Could this potentially influence the developing baby? Different seasons also contain different allergens that could stress the mother’s system and shift fetal development. Even seasonal changes in the mother’s diet during gestation may be enough to cause issues down the line.

What can we do?

Should people who were born in the spring and winter start worrying about their mental health? Should prospective parents attempt to plan their conception around the seasons?

There's no need to panic.

The effects found in this research are relatively small and by no means seal anyone’s fate. In the future, doctors may provide susceptible newborns with extra vitamin D or light box therapy. Mothers may receive special treatments to protect them from infections and allergens. As neuroscience grows and develops, more risk factors will be identified and more solutions crafted.

In the meantime, perhaps we should meditate on the fragility of our brains. If our season of birth is powerful enough to shift our mental health, what else could be holding us back?

Contributed by Courtney Lopresti, M.S.