Does the pill change your mood or your weight? What the largest studies found
A million-woman Danish cohort found a modest rise in antidepressant use among hormonal contraceptive users. A Cochrane review of weight found no evidence the pill causes weight gain.
The two side effects women most often ask about before starting hormonal contraception — mood and weight — have very different evidence behind them. The largest study of mood found a real but modest association: in a Danish cohort of more than a million women, hormonal contraceptive users were somewhat more likely to start an antidepressant afterwards [s1]. The largest synthesis of weight found the opposite kind of answer: no evidence that combined hormonal contraceptives cause weight gain at all [s2].
Neither result is as tidy as the confident claims made on either side of the debate, and the difference between an association and a proven cause matters in both directions.
Mood: a signal, not a verdict
The mood question was addressed by a nationwide prospective cohort study in Denmark that linked the national prescription register to the psychiatric register [s1]. It followed 1,061,997 women and adolescents aged 15 to 34 who had no prior depression, over a mean of 6.4 years, and asked whether starting hormonal contraception was followed by a first antidepressant prescription or a first depression diagnosis [s1].
Compared with non-users, users of combined oral contraceptives had a relative risk of first antidepressant use of 1.23 (95% CI, 1.22-1.25) [s1]. The association was larger for some other formulations: 1.34 for progestogen-only pills, 1.4 for the vaginal ring, and 2.0 for the transdermal patch [s1]. Adolescents showed the strongest associations of any age group [s1].
Those are relative increases on a low baseline, not a doubling of most women's absolute risk, and the study's design cannot prove the contraception caused the depression. Women who seek out or stay on a hormonal method may differ from those who do not in ways that also affect mood; the register captures prescriptions and diagnoses, not the lived experience of the millions of women for whom the methods cause no mood change at all. What the study establishes is that a real signal exists at the population level, concentrated in the first months of use and in younger users — enough to take a woman's own report of a mood change seriously, and not enough to tell any individual what will happen to her.
Weight: a belief the trials do not support
The weight question has a clearer answer, and it is not the popular one. A Cochrane systematic review pooled 49 trials containing 85 weight-change comparisons across 52 distinct contraceptive pairs or placebos [s2]. The four trials that included a placebo or no-treatment group "did not find evidence supporting a causal association between combination oral contraceptives or a combination skin patch and weight change," and most head-to-head comparisons of different formulations showed no substantial difference either [s2].
The reviewers' conclusion was carefully bounded: the available evidence was "insufficient to determine the effect of combination contraceptives on weight, but no large effect was evident" [s2]. In other words, they could not rule out a small effect, but there was no sign of the meaningful weight gain that many women and clinicians assume is a given — a belief the review notes can itself deter women from starting or continuing a highly effective method [s2].
The honest limit here is on the tools, not the finding: too few trials used the placebo group needed to separate the contraceptive from ordinary weight change over time, and the reviewers call for exactly those trials [s2].
Libido, and what is missing
On the third question women often raise — sexual desire — the evidence is thinner still, and neither of these two large studies was designed to measure it. That absence is itself worth stating plainly: the effect of hormonal contraception on libido is poorly characterised by high-quality trials, which is why this piece does not offer a number for it.
Taken together, the strongest available evidence says a modest, population-level association exists between hormonal contraception and later depression, especially early and in adolescents [s1], while the fear of weight gain from the combined pill is not supported by the trials that exist [s2]. Both conclusions are more useful for being narrow.
This article is informational and is not medical advice. Anyone weighing a hormonal contraceptive, or noticing a change in mood after starting one, should discuss it with a clinician.
Sources
- Association of Hormonal Contraception With Depression — JAMA Psychiatry, 2016-11-01
- Combination contraceptives: effects on weight — Cochrane Database of Systematic Reviews, 2014-01-29
Sources
- Association of Hormonal Contraception With Depression — JAMA Psychiatry , November 1, 2016
- Combination contraceptives: effects on weight — Cochrane Database of Systematic Reviews , January 29, 2014
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