A Danish study of women using the birth control pill has found a significant association between female oral contraception and depression, a conclusion which had so far been speculated upon but had lacked scientific backing.
Researchers at the University of Copenhagen reviewed the medical records of over one million Danish women between the ages of 15 and 34 over a six year period and found that 23,000 of them had been diagnosed with depression and a total of 133,000 had been prescribed anti-depressants. None of the women in question had a previous history of depression before being prescribed the pill.
“Use of hormonal contraception, especially among adolescents, was associated with subsequent use of antidepressants and a first diagnosis of depression, suggesting depression as a potential adverse effect of hormonal contraceptive use,” say the study’s authors, whose work has been published in the Journal of the American Medical Association Psychiatry.
The study found that women who used the combined oral contraceptive –the most commonly taken, containing both the hormones estrogen and progestogen – were 23 per cent more likely to take antidepressants, with an even higher association (34 per cent) among those taking the progestogen-only form of the pill. Even more remarkable, researchers found that adolescents on oral contraception were 80 per cent more likely to take antidepressants.
While depression is commonly listed as a potential side-effect of the pill, the exact nature of the relationship between the two is still unknown. Yet, the link is generally attributed to the fact that because birth control pills interfere with normal hormone regulation – and hormones are important factors in mood regulation, the pill is likely to have an effect on mood. As well, studies have shown that estrogen, aside from its reproductive function, has an influence on a range of nervous system attributes including cognitive functioning, fine motor skills, pain mechanisms and, notably, mood.
“Hormones are instrumental in regulating and effecting our emotions,” says clinical psychologist John Mayer, in conversation with Self magazine. “The action of birth control pills is directed to hormonal regulation; therefore you have the perfect storm to set the table to have consequences on mood.”
A 2009 study found that 44 per cent of Canadian women used oral contraceptives. Only 2.3 per cent of women were found to be using the IUD or intra-uterine device, recommended by health care professionals and chosen by the American Academy of Pediatrics as the most effective contraceptive method for teenage girls. In 2012, Health Canada approved the use of the lowest-dose estrogen pill on the market.
The new study’s authors advise that further research is needed to fully investigate the link between the pill and depression, and health care advocates have been quick to point out that while the extensive study clearly identifies an association between the pill and depression, the nature of the causal relationship is not yet known.
“This study does not show that the pill or other hormonal contraceptives play any role in causing depression,” says Genevieve Edwards of Marie Stopes International, an international non-profit focusing on reproductive health, in conversation with The Independent. “However we know that hormones can influence mood and behaviour and we will be closely monitoring any further research.”