The study in question was carried out in Denmark by the University of Copenhagen. It reviewed the medical record of over a million women aged 15 to 34 years, all with no prior history of depression over a period of time. The results have since been published in a well-respected journal, JAMA Psychiatry.
The study was classed as a large cohort study. These follow a group of people up over time to see what happens. It does not prove causation. This means a cohort study is unable to prove that contraceptive methods are directly responsible for depression in these women. It has however identified a possible link between the two.
Researchers identified that individuals who took the pill were significantly more likely to be taking antidepressants as well. They found that women who were taking the oral contraceptive pill were 23% more likely to be taking antidepressants than their counterparts. Similar, or more marked results were found for people using other hormonal methods of contraception as well.
They found that the risk appeared to decrease with age, so teenagers using hormonal contraception appeared to be at the greatest risk.
The study looked at different forms of hormonal contraception including the combined oral contraceptive (COC), the progesterone-only pill (POP, also known as the mini pill), the contraceptive patch and the hormonal intrauterine device (IUCD). It found a possible link between all of them and increased rates of depression.
Researchers analysed the results to see if they could see any other causes or links that may be responsible for these results, but they were unable to find a link common to different ages of women across all forms of hormonal contraception.
Prior to this study, there already was existing evidence to suggest hormonal contraception can affect moods, in particular raised progesterone levels seeming to cause lower mood. This study would support this suggestion.
Further research is required to confirm these results can be repeated in different groups of people and to see if there is a direct causal link. If the association were proven, depression would need to be added as a possible side effect of using hormonal contraception.
What should women taking these forms of contraception do?
At this point, the National Health Service (NHS) advises that women should not be deterred from taking the pill on the results of this study alone. Different people react in different ways to different contraceptives, and as such, the best advice is to consult your GP if you are concerned.
Do not stop your contraception without seeking medical advice first. Your GP will be able to discuss the risks and benefits of different contraception types and help find the most suitable method for you.