The greatest risk seems to be with the combined oral contraceptive—containing a mixture of hormones—which is the most commonly-prescribed version of the Pill. Women taking the combined Pill were 25 per cent more likely also to be taking an antidepressant, but the risk rose to 80 per cent among teenage girls aged from 15 to 19.
The risk has been highlighted in a major research study, involving more than one million Danish women aged between 15 and 34. On average, the women were 23 per cent more likely to suffer from depression than those not taking the Pill, and were taking an antidepressant for the first time.
The risk rose to 34 per cent in those taking progestin-only pills, which use synthetic progesterone, and it doubled for women using contraceptive patches.
Researchers from the University of Copenhagen suspect that progesterone may be to blame for the depression as previous studies have shown it has a negative effect on mood, especially during the menstrual cycle. In particular, it may interfere with the nervous system.