It might sound more like astrology than science, but it turns out when you were born can have a significant impact on your health. A number of studies in recent years have found links between birth month and a range of diseases, psychiatric conditions, and even general personality traits like impulsiveness and irritability. But the most recent study to look at the impact of birth season on health took a slightly different approach: instead of looking at specific disorders, researchers attempted to determine whether people born during particular seasons are just, generally, healthier. 

In the study, published this week in Heliyon, researchers identified indicators of childhood and adulthood health like birth weight, adult body size, and puberty timing. They knew that vitamin D exposure in utero could have a significant impact on future health, and wondered whether exposure to sunlight during the summer months could promote fetal absorption of vitamin D—and therefore, make for healthier babies. 

Using a data set of around 450,000 men and women, they found that children born during the summer months were, in fact, likely to be heavier at birth, and taller as adults. They also found that women born during the summer were more likely to start puberty later—which, Science Daily notes, is “an indication of better health in adult life.” According to Science Daily, it was the first study to link birth month with pubertal timing. 

Though the researchers believe their findings support the hypothesis that vitamin D from sunlight affects fetal health, they note that more research is still needed to make a causal link. However, it is clear that birth month can have a significant impact on overall health during adulthood.

The lead author of the study, Dr. John Perry, explained the significance of these findings to Science Daily, saying, "When you were conceived and born occurs largely 'at random’—it's not affected by social class, your parents' ages or their health—so looking for patterns with birth month is a powerful study design to identify influences of the environment before birth.”

[h/t: Science Daily]