The Pill is one of the great success stories of modern medicine. When it became widely available in the 1960s, it helped to revolutionise the role of women in society by giving them unprecedented control over their fertility.
Today, more than 100 million women around the world take hormonal birth control pills and they are particularly popular among teenagers.
The Pill is, of course, a highly efficient method for preventing unintended pregnancies. Even some women who are not sexually active use it for other reasons, including to reduce menstrual pain or treat acne. However, it was originally developed as a medication for adults, and much remains unknown about the potential side effects for younger users.
A sensitive period
Puberty is a critical life stage that is marked by rapid growth and changes in the body and brain. In animals, sex hormones such as estrogen and progesterone are known to affect how the brain develops during puberty. If the same is true for humans, taking synthetic estrogen and/or progesterone - core ingredients found in most formulations of the Pill - during this sensitive period could affect development in ways that have long-lasting consequences on mental health.
Overall, research has yielded mixed findings about the relationship between hormonal contraceptive use and depression. Some studies have found no relationship, and others have found a lower risk of depression in adult pill users compared to non-users.
Recently, however, the largest study to date on this topic - which included over 1 million women living in Denmark - concluded that women who are using the Pill or other hormonal contraceptives are at an increased risk for depression. The study also showed that this relationship was strongest in teenaged women.
Increasing risk of depression
Our latest study, published in the Journal of Child Psychology and Psychiatry, goes beyond prior research by examining whether contraceptive pill use might not only predict depression risk in the short term but also in the long term. We examined data on 1 236 women between the ages of 20 and 39 enrolled in the National Health and Nutrition Examination Survey who had provided information about their history of contraceptive pill use.
Almost half of the women in the sample had first used contraceptive pills as teenagers; these women were at a higher risk for being clinically depressed (16%) years later, compared to women who had never used contraceptive pills (6%), and also compared to women who had only started taking contraceptive pills as adults (9%).
Choosing the Pill
The decision to take hormonal contraceptives is a very personal one, and we emphatically support the UN's declaration that access to contraceptive information and services is a universal human right. There are clear benefits to using the Pill and many women do not experience adverse side effects.
We do believe that there is an urgent need for more research on this topic. We do not believe that all women are likely to experience the same side effects when they take contraceptive pills. Thus, any blanket statement suggesting that teenagers should or should not follow a specific course of action regarding the use of hormonal contraceptives is, in our opinion, premature.
We do, however, hope that our research might prompt teens and their parents to talk to their doctors about the risks and benefits associated with different options that are available to them, especially if they have a family history of depression or other reason to think that they might be particularly vulnerable to certain side effects of these medications.