What happens to your brain when you fall in love? Is being in love just something you feel, or is it more than that? There's reason to suspect that that your intimate social experiences may affect the actual biochemistry of your brain.
Recent science suggests a fascinating association between being in love and peripheral serotonin, a chemical produced within our brains to help us regulate mood and behavior. You might think of it as a happy neurotransmitter; deficits of it are associated with challenges such as depression, and drugs such as SSRI (selective serotonin reuptake inhibitors) work by allowing the presence of more serotonin.
It seems reasonable to predict that romantic love would be associated with a calming effect and potentially higher levels of serotonin. Romantic love is complex, however, and need not be peaceful: Passionate interest in someone can spark obsessive thinking and the type of heightened awareness linked to jealousy or anxiety. This would potentially suggest an inverse relation with serotonin.
Langeslag and colleagues (2012) studied this issue in depth. These researchers invited 10 men and 10 women who professed to be in love, and 10 men and 10 women who were not in love, into the lab to complete a series of questionnaires and to have samples of their blood plasma taken.
What did they learn about how the serotonergic system might be linked to romantic love? There were mixed results overall, but they suggest a link.
For men, being in love was tied to lower levels of peripheral serotonin; women in love, however, measured higher levels of serotonin than their counterparts who indicated they were not in love. Perhaps falling in love is a mood lifter and stabilizer for men, but it might have a different effect on women. This is in line with basic gender differences in romantic relationships, including observed differences in jealousy.
Interestingly, for women (but not for men), more obsessive thinking about a romantic partner was associated with more serotonin, which seems to run counter to expectations. Why was this? The authors offer no solid explanation. The pattern we might anticipate would be the reverse—more obsessive romantic love, less serotonin.
At this point, findings are correlational, rather than experimental, but they do hint at the possibility that love is much more than skin deep.
Langeslag, S. J., van der Veen, F. M., & Fekkes, D. (2012). Blood levels of serotonin are differentially affected by romantic love in men and women. Journal of Psychophysiology, 26, 92-98.