Love and biology are deeply entwined. Love can make a heart raceand a lack of chemistry can turn romance into friendship. But justwhat is the nature of this link? Can biochemistry causelove?

Dr. Hagop Akiskal won the Ig-Nobel prize in Chemistry for tryingto answer this very question. The Ig-Nobel prizes are organized bythe Annals of Improbable Research and distributed by Nobel Prizewinners. They are designed to celebrate research that “makes peoplelaugh and then makes them think." Akiskal’s work on how love looksa lot like obsessive-compulsive disorder does just that.

Akiskal is the director of the International Mood Center at theUniversity of California, San Diego. Much of his career has beendevoted to understanding and redefining illnesses such asdepression and bipolar disorder. These topics may seem a long wayoff from love, but after meeting Akiskal it is easy to imagine whyhe was drawn to researching romance. Part scientist, part poet,Akiskal has always been fascinated by love and determined tounderstand the things that fascinate him.

Born in Armenia just one generation after the Armenian Holocaustof the early 1900s, Akiskal’s natural curiosity and interests drovehim toward literature and other intellectual fields that wereconsidered controversial at the time. His family pushed for him togo into a career that would be less dangerous. “They were more forme to do something solid like become a doctor or an engineer,fields where there was no controversy. Intellectuals are dangerous,they go to dangerous places or say dangerous things and I was knownfor that,” says Akiskal.

Akiskal landed in medical school but this did nothing to deterhim from saying controversial things. Disillusioned by the waypsychiatry was approached in the 1960s and worried by the chasmthat existed between biology and psychiatry, Akiskal developed aradical theory stating that behavior, emotion, neurochemistry andneurophysiology were all related. Akiskal submitted his“Integrative Theory” to Science. “I had the daring idea of sendingit to Science. I thought it was important enough. Science, even inthose days, was the standard. It was mainly astrophysics andbiology. I think there had only been one psychiatrist published inScience before. They liked it and there it is; it’s history. At theage of 26, I became very famous.” This notoriety led to hisappointment as Senior Science Advisor to the Director of theNational Institute of Mental Health.

It was during this time that Akiskal met Dr. DonatellaMarazziti, an Italian scientist who had become interested inobsession and how much it resembled another human condition: love.The similarities between the early stages of love and obsession areeasy to see. People are often preoccupied with the object of theiraffection and unable to focus on daily activities. Marazziti’sgroup had recently implicated a particular seratonin transporter inobsessive-compulsive disorder. With Akiskal’s help they wanted tosee if this transporter might also play a role in the preoccupationthat can accompany love.

To do this they talked to participants who claimed to be inlove. Importantly, these participants were preoccupied with theirlove object for four hours or more every day. People preoccupied byan object of obsession for four or more hours a day are consideredto have moderately severe obsessive-compulsive disorder.

Levels of the 5-HT seratonin transporter were found to besignificantly decreased in participants in love and participantssuffering from obsessive-compulsive disorder when compared to anormal “control” group (Marazitti et al, 1999). This evidencesupported the theory that obsessive-compulsive disorder and lovehave a lot in common biochemically. It also implicated serotonin asthe chemical behind romantic love.

One of the hallmarks of romantic love is that it is fleeting.Even when couples stay together they generally settle into a morecomfortable stage in which preoccupation decreases and they areable to function more normally outside of the relationship.“Romantic love is something that starts at one point and ends atone point. Mercifully it ends because it’s such an intense emotionthat it must end at some point,” says Akiskal. What does this meanfor the biology? In the follow up to this study Akiskal andMarazitti found that when these participants were re-tested 12-18months later their 5-HT levels had returned to normal. Theparticipants reported that they no longer felt distracted andpreoccupied with the object of their affection. If serotonin is thebiochemistry of love, and if it fades, how does anyone staytogether?

Research from the prairie vole, a mammal that mates for life,suggests this may be the work of yet another chemical: vasopressin.After sex male prairie voles express high levels of vasopressin.They become devoted to their partner and protect her from theattention of other males, but if vasopressin expression is blockedthe male prairie vole fails to become devoted after mating andleaves the female vulnerable to the attention of other males.Vasopressin isn’t just released after sex. It’s elevated in boththe male and female during pregnancy and has been shown to increasein males just from holding a baby. Human males with a particularvariant of the vasopressin receptor have been shown to be lesslikely to get married and more likely to have spouses who areunsatisfied with the marriage when they do. Vasopressin may haveevolved as a way to bind couples together to care for young.Serotonin may be the chemical behind love, but vasopressin seems tobe the chemical of monogamy (Young, 2009).

In the last decade a multitude of hormones have been implicatedin regulating the type and intensity of love that a personexperiences. Dopamine and endorphins play their own role inromantic love, and oxytocin and testosterone can affect long-termlove. These biochemicals not only interact with the cells of thebrain; they interact with one another. In addition to thiscomplicated biochemistry there is another factor, which Akiskal isthe first to point out: “Romantic love is much more than aserotonin receptor. It’s immensely more; it’s somewhere between theatoms of the cells, the subatomic particles, all the way beyondpoetry and music and joy and intense happiness which isintangible.”

References:

Marazitti D, Akiskal HS, Rossi A, Cassano GB. Alteration of theplatelet serotonin transporter in romantic love. Psychol. Med. 1999May;29(3):741-5.

Young LJ. Being human: love: neuroscience reveals all. Nature.2009 Jan 8, 457(7226):14

Author: Jennifer Rust for MySDscience

March 24, 2009