A study recently published in the JAMA Psychiatry tried to answer that question. Being the adolescent medicine doctor that I am, I had to carefully study this study as I prescribe hormonal birth control to teenagers on a daily basis. The study compared the rate of depression in over 1 million Danish women 15-34 years old who were using hormonal contraception (combined oral contraceptives, progestin-only contraceptives, the patch, the vaginal ring, or levonorgestrel-IUDs) compared with non-users, tracking them over an average of 6.4 years.
Their results indicated that adolescents (15-19 years old) on hormonal contraception were approximately two to three times more likely to be diagnosed with depression or to be prescribed antidepressants than non-users. They found that adolescents had higher risks than older women, and that the risks peaked after 6 months of use.
In some ways, it was a well-designed study: Large study population? Check. Comparison group? Check. Followed over time? Check. And yet it has flaws and the findings need to be taken with a grain of salt.
The study should have collected data on why women started on hormonal contraception. Not all women on hormonal contraception are using it for birth control. The study excluded females who had diagnoses of polycystic ovarian syndrome (POS) or endometriosis because hormonal contraceptives are used to treat these problems. Hormonal contraception is also used to help individuals with a depressed mood who have premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD). Many times an antidepressant is needed as well. If the teens started antidepressants during the study, was the depression from the PMS or PMDD or was the depression from the hormonal contraception? We don't know, and these women should have been excluded from the study.
The study should have collected data on whether women had previous abortions. In the U.S., one in three women get pregnant before the age of 20 and one in three pregnant teens have abortions. Compared with women who have abortions in adulthood, teens who have had abortions are two to four times more likely to commit suicide and three times more likely to be admitted to mental health hospitals. If the teens started antidepressants during the study, was the depression a consequence of the abortion or was the depression from the hormonal contraception? Again, we don't know, and these women should have been excluded from the study.
The study should have collected data on whether the teens had early casual sex. A different study published in the Journal of Abnormal Psychology found that teenagers who engage in casual sex (sex outside of a romantic relationship) were more likely to suffer from depression than their peers who did not engage in casual sex. If the teens in the JAMA Psychiatry study started antidepressants during the study, was the depression a consequence of the early casual sex or was the depression from the hormonal contraception? Here again, we don't know based on the data provided in the JAMA Psychiatry article.
My advice is to look at the big picture when looking at the study's results:
1) The population was big but the numbers are small: Among women who did not use hormonal birth control, an average of 1.7 out of 100 began taking antidepressants in a given year. That rate increased to 2.2 out of 100 if the women took birth control. (I am unable to calculate analogous rates for teenagers as the number of teens was not included in the article.) Both numbers are small, and the increase is only 0.5 out of 100, or 1 out of 200. That's one case of depression among 200 individuals.
2) Teens on hormonal contraception are watched closely for signs and symptoms of depression: They are asked to come in for office visits at least twice a year so we get to ask them about their mood. On the flip side, there are many teens with depression who don't see their doctors regularly and might not get diagnosed with depression.
3) Sexually active teenagers are likely to get pregnant if they don't use hormonal contraception. Teens having unprotected sex have a 90-percent chance of becoming pregnant within a year. If they are using condoms to prevent pregnancy, they often don't use them every time; 1 in 3 males and 1 in 2 females reported that they or their partner did not use a condom the last time they had sexual intercourse. These teens are not only at risk for pregnancy, they're also at risk for sexually transmitted infections.
4) What is big is the risk of problems a teen mother often faces including dropping out of school, unemployment and depression. Even the children of teen mothers are at risk of suffering big consequences: living in poverty, poor school performance, becoming involved in crime, drug and alcohol abuse, and eventually becoming teenage parents themselves.
Big take-home point from this study: Our sexually active teenage girls should be on some form of hormonal contraception (with condoms).