Does birth control really cause depression?

When I was in my second year of university, I switched my birth control to the patch, thinking it would save me from my near-constant failure to remember to take the pill every day. After an unusually tearful month, I sat sobbing on my bed and tore it off my body. I felt better within days.

Moodiness is one of the top complaints women have about birth control. “Every single doctor has put someone on the birth control pill who has had some adverse mood effects,” says Jerilynn Prior, a doctor and professor of endocrinology at the University of British Columbia. “This isn’t a secret.”

But it's also not an area of study that's been sufficiently researched. So another popular anecdote is one in which a woman raises this change in mood with her doctor, and is told there is no proven link between hormonal birth control and depression. She leaves feeling like her experience is being ignored, or, worse, that it's all in her head.

So when a recent large-scale Danish study found that women taking hormonal birth control were indeed more likely to be depressed, it went viral. A closer look at the study, however, reveals that while it is the first of its kind to establish that link, we're no closer to proving the link than before.

Related: Gynaecologists use IUDs. Why don’t the rest of us?

The study looked at more than 1 million Danish women between 15 and 34 years old, and found that women using hormonal contraception were 23 percent more likely to be prescribed antidepressants for the first time. The risk peaked two to three months after they were first prescribed birth control.

Experts say, however, that despite its large size, this study can’t prove cause and effect. “This [type] only shows an association,” explains Rob Dmytryshyn, medical director of the Bay Centre for Birth Control at Toronto’s Women’s College Hospital. “We know that people who smoke also drink more alcohol, for example. But does that mean smoking causes drinking?”

There’s also the question of how significant the difference really is. The study found that 1.7 percent of Danish women who aren’t taking hormonal birth control will be prescribed antidepressants. The figure is only slightly higher — 2.2 percent — for those who are on it. “That means on average for every 200 new hormonal contraceptive prescriptions, there will be one extra prescription for antidepressants,” Dmytryshyn says.

And there are some issues with the quality of the data itself. Since the study was based on information from national databases, the researchers didn’t have access to details about the women's health and lives. While they controlled for some variables that might have influenced the results — like when the women became sexually active — there’s still the possibility that another factors, such as access to health care or willingness to take medication, played a role.

Related: From birth control to fertility, the 3 big trends in reproductive health 

The researchers also didn’t find what’s called a dose effect — that higher doses of the birth control hormones were more likely to result in antidepressant prescriptions. In fact, the women with IUDs had the highest risk of antidepressant usage, despite the devices having as little as 10 percent of the hormones found in other kinds of birth control.

“This study has important and significant limitations,” says Wendy Norman, an applied public health chair in Family Planning Public Health Research and an associate professor at the University of British Columbia. “It should be taken with a large cup of salt.”

So this study doesn’t prove the link, but does that mean one doesn’t exist? Not at all, it just means more research is needed. A review published in August that systematically sifted through 30 years of research on combined hormonal contraception pointed out that studies generally did find a small number of women who had adverse mood changes after taking birth control. (It also found that some women find their mood is better.)

If you’re worried about becoming depressed — or suspect that your depression is linked to being on the pill, raise it with your doctor, says Prior, and ask about non-hormonal birth control options. The copper IUD in particular is highly effective and completely hormone-free. “There are other effective contraceptive methods, but [prescribing] the pill can be like a reflex,” says Prior, who suggests women who might be concerned can always switch to a non-hormonal method and track their mood to see if it improves.

“Certainly, if my patients start to feel unwell in any way after going on hormonal birth control, I’d say come back to me to discuss it,” says Ashley Waddington, a gynaecologist and assistant professor at Queen’s University. “But I’m not going to say don’t go on this method because it’s likely to cause you a mood disorder. That’s just not true.”

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