However, we do not yet have an answer that definitively clarifies the existence of a link between the pill and mood. The main problem is that most of the studies conducted so far have been conducted on a cross-sectional sample, that is, they have monitored a group of women who use the pill, comparing them with a group that does not use the drug. “It is not taken into account that women who tried the pill and experienced negative effects on mood or sexuality then stopped taking it – explains Cynthia Graham, professor of sexual and reproductive health at the University of Southampton and director of the Journal of Sex Research – It is the so-called survival biasor healthy user bias“.
Studying whether a drug causes ailments such as depression and suicidal instincts is very complicated. External factors such as socioeconomic background, marital status, a family history of mental disordersfor example, they are all elements that influence the conclusions of research.
The impact of the 2016 Danish study
The most famous research on the subject is one Danish study of 2016led by Charlotte Wessel Skovlund, who followed over a million women aged between 15 and 34 for over 14 years. The study reported that women aged 15 to 19 who took oral contraceptives were about 80 percent more likely to be diagnosed with depression or prescribed antidepressants. Participants who took progesterone-only contraceptives were twice as likely to develop depression.
The study did news a international levele several women had their experiences with the drug confirmed. It wasn’t just about people taking the pill: other long-term contraceptive methods such as hormone implants, patches and intrauterine devices also appeared to have a negative effect on mood. The Danish studio, however, has not put an end to the saga.
“It was a well done study in what is possible to do with observational data“explains Ruben Arslan, personality psychologist at the University of Leipzig. The key term in this case is”observational“: the main problem of the study can be summarized with the well-known principle according to which the”correlation does not imply causation“: a link between contraceptives and depression, but not conclusive proof that the latter is caused by the former. The study authors checked for some factors that could affect their results: they excluded women who had been diagnosed with depression prior to the study and women who were pregnant or who had given birth in the past six months (to avoid including people potentially prone to postpartum depression). To identify depression, the study used a medical diagnosis or a prescription for an antidepressant as indicators; in many cases, however, depression she is neither diagnosed nor treated.
More effective studies
The best way to answer any scientific question is to carry out one randomized placebo-controlled study, the gold standard in research. Instead of looking at the behavior of the pill in the world – where other factors of all kinds might come into play – this type of study involves dividing the participants into two very similar groups; one group is given the pill and the other a placebo, without telling the participants which of the two groups they belong to. This way you can be much more confident that any differences found between groups are caused by the pill and not by other factors.