Hormonal contraception including the pill regulates estrogen and/or progestin levels to control the ovulation cycle. And a long line of research shows that hormone levels in turn influence mate preference -- choosing a good mom/dad over a sexy alternative depends on testosterone and estrogen. Now a study published in the June issue of the journal Personality and Individual Differences asks a fascinating question: if hormone levels influence mate choice, and hormonal contraception changes these levels, what happens when a woman enters a relationship and then changes her use of hormonal contraception? Does she, "experience changes in her relationship since her preferences become incongruent with those prevalent at the time of her partner choice?" the authors ask.
In other words, if a woman picks a guy while off the pill and then goes on the pill (or vice a versa), does she still like him? In this case, the researchers limited their exploration to jealousy. Basically, they used a 15-question survey to measure jealousy in 129 young women currently in relationships and compared this measure to changes in their use of hormonal contraception.
Here's what they found:
First, women on the pill or other hormonal contraception reported overall higher levels of relationship jealousy (but this may be explained by sample bias). Then the researchers wondered what happened when a woman's hormonal contraception status changed from the time she started her relationship, either going on or off the pill. They found that, "Women whose contraceptive use status was incongruent with when they met their partner were significantly more jealous than those women whose status was congruent."
So the answer is yes: if you created your mate preference at one hormone level, found a mate, and then switched your hormone level, you may also have switched your mate preference and so feel more relationship jealousy than a woman who was on or off the pill the whole time.
The authors write, "Switching use of hormonal contraceptives within an existing relationship may shift female preferences, and this may change the way that women perceive their partners."