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For years, unsuspecting girls and women swallowed their daily birth-control pill without much thought as to why their moods were suddenly so erratic or why they seemed to constantly feel depressed. Now, new research is shedding light on the link between hormonal balance and female mental well-being. And the hormonal contraceptive, it is becoming clear, may be a contributing factor to destabilizing that well-being.
Seeking to address this question, a group of Swedish researchers undertook to examine the impact of hormonal contraception on psychotropic drug use in Swedish women, focusing in on one specific group: adolescent girls. “The burden of depression and anxiety disorders is greater in women,” they open by way of background, “and female sex hormones have been shown to affect mood.” Furthermore, it is well-known now that hormonal contraception can cause psychological side effects, which are in fact one of the most cited reasons women give for discontinuing them. Visits to mental-health practitioners have been increasing among Swedish women recently, and so the researchers seek to better understand the link between hormonal contraceptive use and mental health. The researchers hypothesize that the incidence of negative mental health outcomes will be higher in adolescent girls in comparison with adult women, due to something they call “selective discontinuation bias.” In other words, girls and women who experience negative mental health side effects from their birth control are more likely to discontinue use of hormonal contraception (HC), so that cohorts of adult women using HC will have a natural selection bias toward fewer mental health problems.
The researchers use a large nationwide cohort of 815,662 women during the years 2010-2011 to examine these questions. From their first HC prescription, all women were followed for one year, and the previous four years were also recorded. Non-users were defined as those who did not fill a prescription for HC in this time period. Emergency contraception, because it can be obtained over the counter in Sweden and thus can’t be tracked, was excluded. “The outcome of our study,” the researchers report, “was use of psychotropic medication defined as filling at least one prescription with anxiolytics, hypnotics and sedatives or antidepressants . . . during the one-year follow-p, from the first dispensation of HC or 31 December 2010, if the individual did not use HC at baseline.” The use of such medications was considered a “proxy” for mental-health problems. The researchers also controlled for a range of variables, including socioeconomic status and a number of health conditions correlated with the use of HC that they felt may also impact mental health. They separated the women into age categories, ranging from 12-30 years old.
The results supported the researchers’ hypothesis. In their sample, roughly half of the women were users of HC. “Among HC users the incidence of psychotropic drug use was 3.7%, while this figure was 2.5% for non-users.” Furthermore, “Patterns of HC use varied with age.” The researchers observed a “strong association” between the use of HC and the use of psychotropic drugs “in adolescent girls, which decreased with age to disappear after adolescence.” They observed this pattern for all types of HC, but the strongest association was for adolescent girls aged 12-14 who used a “non-oral progesterone-only method such as a skin patch or intravaginal ring.” And although the association between HC use and psychotropic drug use was insignificant for adult users, for these non-oral forms of HC, some association did linger for both adolescents and adult women. The DMPA injection had the strongest association with negative mental health outcomes in adult women, while for adolescent girls, the levonorgestrel-containing IUD was the strongest.
The researchers conclude, “Our findings show strong associations between the majority of hormonal contraceptives and subsequent use of psychotropic drugs in adolescent girls without previous psychiatric morbidity.” “Our results could be explained,” the researchers posit, “by a selective continuation bias.” That is, those women who find themselves especially sensitive to HC may have discontinued use before becoming adults. The researchers also speculate that adolescent girls may be more sensitive to the hormones in contraceptives, or that HC use may be an indicator of earlier sex initiation, which is a known factor in poor mental health outcomes.
In delineating limitations to their study, the researchers list one which should be especially noted: “Another aspect to consider is that not all women with adverse mental health effects of HC would have symptoms severe enough to get a prescription for a psychotropic drug, leading to many missed cases. This limitation would therefore suggest that our results are an underestimation of the problem at hand.”
They conclude by highlighting adolescent girls as a population particularly vulnerable to hormonal contraception use, and call for further study. One might suggest, instead, more caution in prescribing powerful hormones to young girls who are still very much in a state of hormonal flux and physical maturation.
(Sofia Zettermark, Raquel Perez Vicente, and Juan Merlo, “Hormonal contraception increases the risk of psychotropic drug use in adolescent girls but not in adults: A pharmacoepidemiological study on 800,000 Swedish Women,” PLoS ONE 13.3 [March 2018]: e0194773, Web. Emphasis added.)