Researchers in Sweden have found that two of the UK's most commonly used contraceptive pills - Microgynon and Rigevidon - may make women feel miserable.
Their study focused on 340 healthy women aged between 18 and 35, and was published in the journal Fertility and Sterility this week.
The women took either a contraceptive pill or a placebo over the course of three months. Volunteers were unaware of which tablet they had been prescribed.
Despite this, participants who took the contraceptive pill - which included the components ethinylestradiol and levonorgestrel - estimated their quality of life to be significantly lower than those who took the placebo.
As well as feeling generally low, the group who were on the pill reported a negative effect on their sense of mood, wellbeing, self-control and energy levels.
However, no significant increase in depressive symptoms were observed by the team at Sweden's Karolinska Institutet.
Ethinylestradiol and levonorgestrel are ingredients that are both used in Microgynon and Rigevidon, two of the UK's most frequently prescribed contraceptive pills.
"Despite the fact that an estimated 100 million women around the world use contraceptive pills we know surprisingly little today about the pill's effect on women's health," says Professor Angelica Lindén Hirschberg, leading the study.
Her colleague and co-lead, Niklas Zethraeus, adds, "This possible degradation of quality of life should be paid attention to and taken into account in conjunction with prescribing of contraceptive pills and when choosing a method of contraception."
The team say the results may be partially caused by irregular pill use. They called for further research into the effect of the contraceptive pill on quality of life and depression.
The combined pill is more than 99% effective at preventing pregnancy, if taken correctly. Around two-thirds of women aged 20-24 use it as a form of contraception in Britain. Side effects include nausea, breast tenderness, bleeding between periods and mood changes.
A Danish study last year found that women using the contraceptive pill were more likely to be depressed than those who did not. However, it was unable to establish a causal link between the pill and depression.
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