The Biochemical Basis of Love

"Anthropologist Helen Fisher...has devoted much of her career to studying the biochemical pathways of love in all its manifestations: lust, romance, attachment, the way they wax and wane...(In her studies) when each subject looked at his or her loved one, the parts of the brain linked to reward and pleasure,--the ventral tegmental area and the caudate nucleus--lit up...Love lights up the caudate nucleus because it is home to a dense spread of receptors for a neurotransmitter called dopamine...which creates intense energy, exhiliration, focused attention...(thus) love makes you bold, makes you bright, makes you run real risks, which you sometimes survive, and sometimes you don't...

"Researchers have long hypothesized that people with obsessive-compulsive disorder (OCD) have a serotonin 'imbalance.' Drugs like Prozac seem to alleviate OCD by increasing the amount of this neurotransmitter available at the juncture between neurons. (Researchers) compared the lover's serotonin levels with those from the OCD group and another group who were free from both passion and mental illness. Levels of serotonin in both the obsessives' blood and the lovers' blood were 40 percent lower than those in normal subjects...Translation: Love and mental illness may be difficult to tell apart...

"Why doesn't passionate love last?...Biologically speaking, the reasons romantic love fades may be found in the way our brains respond to the surge and pulse of dopamine...cocaine users describe the phenomenon of tolerance: the brain adapts to the excessive input of the drug...From a physiological point of view, (couples move) from the dopamine- drenched state of romantic love to the relative quiet of the oxytocin-induced attachment. Oxytocin is a hormone that promotes a feeling of connection, bonding."

Lauren Slater, Love: The Chemical Reaction, National Geographic, February 2006, pp. 35-45