Researchers at the University of Copenhagen in Denmark analyzed health data on over 1 million women in a national healthcare system database between 1995 and 2013.
Compared to non-users, women who used a hormonal birth control pill, patch, vaginal ring, or IUD were 40% more likely to be prescribed an antidepressant medication within six months.
They found that teenage girls aged 15-19 years old on hormonal contraceptives were 80% more likely to start taking antidepressants compared to non-users. The risk was even higher for girls on progestin-only pills.
Older women — average age 25 years old — on hormonal contraceptives were 23% more likely to start using an antidepressant than non-users. Higher rates were observed in women on progestin-only pills.
According to Dr. Øjvind Lidegaard, lead supervisor of the study:
Hormones acting in the same way and on the same centers as the natural hormones might also influence women’s mood or even be responsible for depression development.”
The study does not prove that birth control causes depression. There are many other reasons why a woman on birth control might develop depression or take an antidepressant medication.
However, results of the study were dramatic and not entirely surprising. About 30% of women stop using hormonal contraceptives due to side effects, according to the CDC. Mood changes are one of the most common reasons.
Furthermore, experts have known for decades that sex hormones like estrogen and progestin have a powerful influence on mood and emotions. It is one reason why teenagers can be irritable and depressed during puberty.