There’s always been a simmering opinion in scientific circles that, yes, hormonal birth-control pills may cause depression in some users. Certainly, it’s something women have always believed. Now, a new Danish study of 1 million women—teens included—offers more scientific support for the theory than ever.
Researchers from the University of Copenhagen followed more than 1 million women aged 15 to 34 for an average 6.4 years finding that those on some sort of hormonal control had a significantly higher tendency to have been prescribed anti-depressants by their doctor than those not on hormonal birth control. Interestingly, those using progestin-only pills, IUDs, and the patch had significantly higher rates of diagnosed depression than those taking combination estrogen and progestin pills.
Now, it’s important to note that correlation is not necessarily causality. That is, just because pill users have a higher rate of diagnosed depression does not mean that hormonal birth control is 100% definitely causing mood swings and the blues. It just means it’s really, really, really likely that it is. The work of unpacking these finding and figuring out what to do about them is already underway.
Still, even if we don’t have answers at this time, it is a huge step forward in the clinical recognition of something women have already known, but didn’t have the science or data to explain. We should all be thankful for that.
For more on the study and what it means, visit Time.