A major study has established for the first time that oral contraceptive pills have a negative effect on the quality for women’s lives. Researchers at the Karolinska Institutet in Sweden conducted a randomised, placebo-controlled study to test the effects of contraceptive pills containing ethinylestradiol and levonorgestrel, one of the most common forms of combined contraceptive pills.

Although an estimated 100 million women around the world take contraceptive pills, little is known about their effect on women’s health. There is plenty of anecdotal evidence of women reporting mood swings, irritability and even clinical depression and preferring non-hormonal methods of contraception. Previous studies that have relied on self-reported changes in mood or mental health have found the mental health effects either negligible and even positive. But many factors may affect a person’s mood and so self-reporting has its limitations. Previous placebo-controlled studies have indicated that women taking hormonal birth control were likely to report worse moods and fatigue.

The new study by Karolinska Institutet researchers that has been published in the journal Fertility and Sterility enrolled healthy 340 women between the ages of 18 and 35 and treated them for three months in a randomised trial with either pills with no effect – that is, placebos – or contraceptive pills containing ethinylestradiol and levonorgestrel. Neither the leaders of the experiment nor the subjects knew which women were in which group.

The study found that women who were given contraceptive pills estimated their quality of life to be significantly lower than those who were given placebos. These women reported that both their general quality of life and specific aspects like mood and well-being, self-control and energy levels were affected negatively by the contraceptives. However, there was no significant increase in depressive symptoms.

The research team says that the changes were relatively small and the results must be interpreted with caution. Yet, the findings may be of clinical importance as these factors may contribute to low compliance and irregular use of contraceptive pills.