Women who take hormonal oral contraceptive birth control pills are at an elevated risk of being diagnosed with depression and prescribed an antidepressant, according to one of the largest studies to date examining the link.
The most popular birth control pills in the U.S. combine two hormones, usually estrogen and a progestin. Researchers in Denmark found that women who took a combination birth control pill were 23% more likely to be given an antidepressant while on the pill compared to women not on birth control. And women who took progestin-only pills were 35% more likely to end up taking an antidepressant.
The findings, published in JAMA Psychiatry, are based on the medical records of over 1 million women between the ages of 15 and 34 years old who were tracked over 10 years. None of the women included in the study had a history of significant mental health illnesses.
A higher risk of depression with birth control pills was also associated with younger age. Adolescent girls on the combination pill were 80% more likely to be given antidepressants than those the same age not on any oral contraceptive.
The researchers also found that other types of hormonal contraceptives, such as implants, patches and IUDs (intrauterine devices), were also linked to higher rates of depression.
As to why the hormone-based birth control pills may cause depression, prior research has implicated changing levels of the female sex hormones estrogen and progesterone. Some studies have even argued raising progesterone levels can lower mood.