Most people would blow off any idea of their birth date determining their personality. We’ve heard it before; summer babies like the summer and winter babies like the winter. It may be true, but it could also be that we’re just happy our birthdays are coming up — it’s time to celebrate! A new study from Hungary, however, suggests that our birthdays really can determine our personalities, specifically whether we’ll have mood disorders. And no, this has nothing to do with a person’s zodiac sign.

“Biochemical studies have shown that the season in which you are born has an influence on certain monoamine neurotransmitters, such as dopamine and serotonin, which is detectable even in adult life,” said the study’s lead researchers Xenia Gonda, an assistant professor at Semmelweis University in Budapest, Hungary, in a statement.

The small study involved 366 university students, who filled questionnaires regarding personality traits and temperament. When their birthdays were compared to their survey results, the researchers found that personality types did indeed match each person’s birth date. People who were born in the spring and summer were more likely to be overly positive, which is sometimes called a hyperthymic temperament, and those born in the summer were more likely to have a cyclothymic temperament, characterized by frequent mood swings (bipolar disorder, even). Meanwhile, those born in the fall were less likely to have depressive temperaments, and those born in the winter were less likely to have irritable temperaments.

The researchers admit it’s not entirely clear how something like this happens. Depending on the time of the year, Hungarians may eat more of a certain type of food, with different types of amino acids, which get converted into specific neurotransmitters. For example, heartier winter foods tend to be high in tryptophan, which gets converted into serotonin — dishes like these include veal stew and sweet potato cottage pie.

Of course, this is only speculation. That’s because a study from 2012 found that personalities also matched birth dates, but this time, results were the complete opposite. People born in January were more likely to have schizophrenia and bipolar disorders, while those born from July to September were least likely to have mental health disorders. These findings were far more significant, because the study looked at over 29 million people from England’s population, as well as 58,000 people with mental health disorders.

So, what does all of this mean? It’s likely that a person’s birthdate can predict whether they’ll have mental health disorders or not. But there are so many factors to consider, the least of which is food consumption patterns in a particular region of the world. A mother’s physical activity level, mental health, and vitamin D levels may also play a part. Or, none of this could matter, and the researchers could just be looking for something where there’s really nothing.

Source: Gonda X, Ormos M, et al. Season of Birth Shows a Significant Impact on the Distribution of Affective Temperaments In a Nonclinical Population. At The European College of Neuropsychopharmacology Congress. 2014.