Though many are still skeptical about astrology (someone introduce them to Susan Miller, please), it's a science that dates back to medicine itself. As Lauren Kassell, history and philosophy of science professor at the University of Cambridge, explains, "For centuries it was common practice for educated physicians to use astrology as one of their tools." And, it's no surprise, since the month you were born in can apparently indicate your risk factor for conditions like schizophrenia, multiple sclerosis, sleep disorders, bipolar disorder, and other conditions. It all comes down to your biological clock.
Though we almost always refer to our biological clock in jest, it's important to remember that this circadian rhythm is a very real thing, dictating everything from what time you wake up to the functioning of your vital organs and patterns of social behavior. When this clock faces environmental factors that can permanently and negatively affect it, disorders occur. For example, those born in December are more prone to epilepsy, while those born in August are at a higher risk for autism — all because of the time of year you were born, and subsequent exposure to the elements of nature. Sound crazy? Here's the real, biological process.
When light enters your eye, your suprachiasmatic nucleus (think of it as your brain's master clock) receives a signal. Then, this master clock sends another signal down the raphe nuclei (these release seratonin, which regulates mood, appetite, and sleep). An imbalance from this light-to-receptor system can cause a communication problem with your biological functions. Thus, those born in winter months, when the sun isn't dominant, may experience mental disorders.
Sure, your genetics do play a huge part in your development, but as the Atlantic's Elijah Wolfson notes, it's also about when you joined the world: "Yes, you are born with a single set of genes that determines many of your innate characteristics, but how those genes are expressed is manipulated by your environment and developmental experience." So, while you may not exactly list your birthdate as part of your medical history to your doctor, it's certainly interesting to consider the ways in which the month you were born has a real effect on your everyday life — even if it's not listed in your horoscope. (The Atlantic)