A study published in JAMA Psychiatry last week has shown that women using hormonal contraception are more likely to be treated for depression. Use of the combined oral contraceptive pill (COCP), which is one of the most commonly used forms of hormonal contraception in the UK, was shown to increase the likelihood of being prescribed antidepressants by 23%, and this was even higher with the progesterone-only pill (POP) and Mirena coil at 34% and 40% respectively.
These are quite shocking statistics from a relatively large sample size of over 1 million women. However, I believe we should think carefully before women worldwide start ripping out their coils, and stopping their contraceptive pills.
Whilst the authors have taken several methodological steps to try and reduce the risk of bias in the results, they have been unable to adjust for many large and potentially confounding factors. The numbers in the study are based on registry data and although some social history for each woman was available, including education level and smoking history for a limited number in the cohort, other important factors linked to depression such as drug and alcohol abuse, marital status, employment and chronic disease were not available for the analysis. What this study really shows is association rather than causality. By that, I mean that the take home message is that women using hormonal contraception are more likely to have depression, but with the level of evidence presented in the study, one cannot conclude that the depression is caused as a direct result of the use of hormones. The authors do present some very interesting biologically plausible reasons for why these contraceptives may be associated with depression, however the inability to control for multiple confounding factors means we really should treat these results with caution.
The study has already been very successful at awakening both patients and clinicians to the reality of a link between hormonal contraceptives and depression, which will prompt further research in the field which should aim to ascertain whether there truly is any causal effect of these drugs and devices. The evidence presented is not strong enough to change current practice, although women wishing to cease the use of hormonal contraceptives based on this study must ensure they switch to an effective form of non-hormonal contraception to avoid unwanted pregnancy which also carries a psychological risk. Furthermore pregnancy itself is not without its risks; the suicide rate is 5.2 per 100,000 for women in the UK, and in comparison the number of deaths directly related to pregnancy is currently 2.91 per 100,000 maternities, which is by no means an insignificant number.