Birth Control Pills and Depression
This week a study was published in JAMA Psychology drawing a connection between the use of birth control pills and depression. This was picked up in the popular press, and briefly we were hearing about it in the news and radio. I first heard about on my way to work listening to NPR. The message I got was that a study was just published that showed a link between the use of birth control pills and the development of new depression.
Today I read the actual paper that led to this media frenzy, and not surprisingly the media got it at least partially wrong.
Skovlund et al reported the following
“A total of 1 061 997 women (mean [SD] age, 24.4 [0.001] years; mean [SD] follow-up, 6.4 [0.004] years) were included in the analysis. Compared with nonusers, users of combined oral contraceptives had an RR of first use of an antidepressant of 1.23 (95% CI, 1.22-1.25). Users of progestogen-only pills had an RR for first use of an antidepressant of 1.34 (95% CI, 1.27-1.40); users of a patch (norgestrolmin), 2.0 (95% CI, 1.76-2.18); users of a vaginal ring (etonogestrel), 1.6 (95% CI, 1.55-1.69); and users of a levonorgestrel intrauterine system, 1.4 (95% CI, 1.31-1.42). For depression diagnoses, similar or slightly lower estimates were found. The relative risks generally decreased with increasing age. Adolescents (age range, 15-19 years) using combined oral contraceptives had an RR of a first use of an antidepressant of 1.8 (95% CI, 1.75-1.84) and those using progestin-only pills, 2.2 (95% CI, 1.99-2.52). Six months after starting use of hormonal contraceptives, the RR of antidepressant use peaked at 1.4 (95% CI, 1.34-1.46). When the reference group was changed to those who never used hormonal contraception, the RR estimates for users of combined oral contraceptives increased to 1.7 (95% CI, 1.66-1.71).”
In summary, women who used birth control pills were more likely to also use antidepressants. They concluded that women who use birth control use antidepressants more often, and thus they may be more likely to be depressed.
Here’s what I think about this.
1. It is possible that indeed some women who use birth control pills experience more depressive symptoms that if they weren’t taking the pills. In my career I have prescribed OCPs to thousands of women, and a handful have indeed told me that they felt depressed on the pills. I have also had a few women who reported that they felt like they got depressed after a Mirena IUD was placed. In all of those cases, I changed up their birth control or discontinued it, and at least some of those women felt like their depression went away when we made the change. As such, I do believe that some women feel a depressive effect from birth control. That said, I have prescribed OCPs to thousands of women who did _not_ report that it made them depressed, and in fact they showed no signs of depression at all. Does this mean that the study was wrong or right? No, it just means that not all people react exactly the same to a particular chemical. We are all genetically unique beings, and there are all kinds of genetic variants to the enzymes that metabolize the things we put in our body. It is entirely possible that a small percentage of women have a variant mechanism that leads the metabolism of birth control down a road that makes them depressed. So what this means for me is NOT that we should never use birth control pills for fear of creating depression, but that if women report depression after using OCPs, we should believe them and consider alternate forms of birth control. I was already doing that, so this is nothing new for me.
2. The alternate hypothesis is that the study is wrong. There are lots of ways that this study could be biased in its results. We have to remember that the outcome was not depression, but rather the use of antidepressants. The most significant bias in my mind is a selection bias in women who tend to use synthetic chemicals or not. I have lots of patients who have a general desire to not put synthetic chemicals in their body. Hence, they tend not to use hormonal birth control. If they were depressed, they would also tend to resist the idea of an antidepressant. And in reverse, a women who is totally OK with using birth control may also be totally OK with using an antidepressant chemical medication. The link is there, but its not that the birth control is causing depression. Rather, its that women who use birth control are more likely to accept anti-depressants as treatment for depression. This type of bias is probably impossible to control for, but it certainly could be in play in this study, and could even be the entire reason for the result.
So despite the media hooplah about this study, I think it is much ado about nothing. If a patient feels like their birth control is causing depression, then by all means we should try to go to something else and see if the symptoms improve. If a physician was previously pooh-poohing the idea that OCPs could cause psychological side effects and now this study has enlightened them, then great, but such a physician hasn’t been thinking very hard about the idea and maybe isn’t listening to their patients very well. But if we already realized that a minority of patients may have psychological side effects with birth control, this study adds nothing and we will behave the same.
I think we see the media often grabbing onto new studies and explaining them in a way that is too simple and often missing important interpretation and nuance. This certainly happened with the WHI, which unnecessarily decimated postmenopausal hormone replacement. The use of the power morcellator was similarly destroyed by the media, and the debate on this still rages on. Perhaps we are asking too much of the media to truly understand these things and explain them as a physician would, but it would be nice if they tried a little harder.