Psychology in the News

May 12, 2009

Love, obsession, and chemistry

by Dan Schwarzman

May 22nd (Dont Say That You Love Me) by Phoney Nickle

May 22nd (Don't Say That You Love Me) by Phoney Nickle

What is love, and why does it exist? Chemical similarities have been found linking love to OCD and depression. Anthropologist Helen Fisher PhD of Rutgers University has been doing research on love, which she has divided into three chemically separate states. Fisher says that lust is driven by androgens and estrogen, while romantic love, characterized by intensely emotional mood swings and obsessive craving, is driven by high dopamine and norepinephrine levels, along with low serotonin. The third state, of stable attachment, is driven by the hormones oxytocin and vasopressin.

An evolutionary anthropologist, Fisher explains the evolutionary value of these three states. According to evolutionary theory, adaptations show up in species if they lead to increased survival and reproduction. Fisher says that lust evolved as a mechanism for people to be interested on a basic level in reproduction with others, while romantic love developed to focus one’s mating energy on just one individual. Stable attachment works to tolerate this individual long enough to raise children as a team. The obsessive energy output of being in love might seem illogical in the context of evolutionary theory, especially since love is often not reciprocated, but this ability to forgo short term efficiency in favor of greater long term reproductive success makes sense as an important adaptation for the continuation of the human race.

Interestingly, the low serotonin levels found in romantic love are similar to the brain states of people with OCD. One study compared the brains of 20 subjects who were in love, 20 subjects with untreated OCD, and 20 control subjects. The study found that serotonin levels in the lovebirds and those with OCD were both unusually low compared to the control group (Marazziti,  Akiskal, Rossi, & Cassano 1999).  A plausible explanation is that OCD and love are similarly obsessive, driving urges, and that serotonin is somehow involved with this kind of focused obsessiveness in the brain. Dr. Fisher’s 2002 study found that some infatuated subjects reported thinking about loved ones 95% of the day.

Low serotonin levels are also linked with depression, including SAD, or Seasonal Affective Disorder. A recent study by researchers at McGill University studied the effects of light and lack of light on people’s moods and social interaction, and found that increased serotonin associated with more light causes healthy people to become more socially agreeable (Rot, Moskowitz & Young, 2008). Scientists have picked up on the connection between depression and low serotonin, and most common antidepressant drugs serve to raise serotonin levels in the body.

A frequent side effect of antidepressants is problems with sex and love life, including lack of interest in pursuing potential mates. Studies have put the percentage of patients who complain of experiencing sexual side effects from antidepressants at around 30-40%, but when directly asked whether they are experiencing any issues, up to 73% of patients admit to sexual problems, sometimes unaware that there is a connection to the antidepressants they are taking. It is understandably more difficult to measure blunted romantic feelings than more physical sexual symptoms, such as decreased genital sensitivity, but connections have been drawn from antidepressants to both physical and mental sexual problems.

What does all this mean? Love is an obsessive compulsion that probably evolved as a means for individuals to focus on specific other individuals with enough energy to ensure reproductive success, and possibly long term attachment, which would lead to better chances of survival for offspring. Because love is characterized by obsessive thoughts similar to depression and OCD, it begins to make sense only as an evolutionary strategy. Love is not chemically similar in some ways to stable happiness, but instead includes seemingly inefficient use of energy, as well as frequent disappointment. When seen as an evolutionary strategy to ensure production of offspring, love finally becomes a bit more logical, even if we remain ever susceptible to its emotional highs and lows.


Brink, S. (2007, July 30). Are antidepressants taking the edge off love? – Sure, we know about the sexual side effects of SSRIs. But researchers now wonder if that’s the only aspect of romance the drugs can influence. Los Angeles Times, pp. F8.

Fisher, H., Aron, A., Mashek, D., Strong, G., Li, H., & Brown, L. (2002). Defining the Brain Systems of Lust, Romantic Attraction and Attachment. . Archives of Sexual Behavior, 5, 413-9.

Marazziti, D., Akiskal, H., Rossi, A., & Cassano, G. (1999). Alteration of the platelet serotonin transporter in romantic love. Psychological Medicine, 29(3), 741-745. Retrieved March 3, 2009, from;jsessionid=JwMWBLvJlQYMfp4ypLwTlnJ3Z2GQ5Brzpt5Jf3GfGBdWTL9HGcgt!751744069!181195628!8091!-1

Rot, M. a., Moskowitz, D., & Young, S. (2008). Exposure to bright light is associated with positive social interaction and good mood over short time periods: A naturalistic study in mildly seasonal people. Journal of Psychiatric Research, 42(4), 311-319. Retrieved March 4, 2009, from

Sher, L. (2003). Bright light, serotonin turnover, and psychological well-being. Canadian Journal of Psychiatry, 48(7), 499.

Sexual Side Effects Of Antidepressants Common, But Still Seriously Underestimated By Physicians. (n.d.). Retrieved March 27, 2009, from


  1. I think that perhaps rather than just being productive for creating offspring, perhaps love is also useful largely–i think the article briefly touched on this–the survival of that offspring. If one is romantically attached to the mother, one will be more likely to hunt for both the mother and the child. The obsessive nature of love that is tied to OCD that this article talks about could maybe link to this survival aspect of love.

    Comment by eric schuman — May 13, 2009 @ 10:40 pm

  2. So, could romantic love combined with untreated OCD reach a dangerous point of low serotonin levels; eg, too much obsession with the object of affection, to the point where it prevents other thought and activity? Could someone become dangerously dependent on reciprocation in connection to OCD?

    Comment by Emma Schaeffer — May 13, 2009 @ 10:41 pm

  3. After reading this post, my only question is: What is the definition of love in this experiment? Is love viewed as what is commonly considered infatuation, revolving around obsessive thoughts about another, or is it thought of the type of affection that people in successful, committed long-term relationships feel?
    Although I completely understand the results of this experiment if operational definition of love is infatuation, as I believe the study classified it, I would question whether this is actually love.
    I feel that if I am correct about the definition of love in this study, the results should be rephrased to say that there are similarities between those who are infatuated with another and sufferers of OCD.

    Comment by Eadaoin Harney — May 13, 2009 @ 10:44 pm

  4. I think an interesting follow-up study would be to study animals who mate for life and see how their brain chemistry differs from closely related species (e.g. the prairie vole vs. the montane vole) or even before and after finding a mate.

    Comment by Will Jobs — May 14, 2009 @ 9:14 pm

  5. Wow! Great post, I’ve always wondered what the chemical reasons behind/for love are, and although I’d never thought about it before, the OCD component definitely makes sense. After all, there are the sayings “crazy in love,” or “only fools fall in love.” A component that is missing from the article though are the connections between the neurotransmitters and the qualities that trigger them–ie, what actually CAUSES love.

    Comment by Katie De Heras — December 12, 2009 @ 3:47 pm

  6. Could love and its effects be like that of drug use? And would a withdrawal be like the loss of love and the depression that ensues? After being in love for a period of time one can become addicted to love. Dr. Fisher, who has done extensive research on the effect of love seems to think so. Fisher believes if one person in love is dumped, that person can have real withdrawal symptoms. Even if a person gets over it, they can relapse, simply by memories or objects that they connect with the past loved one.


    Comment by 105 student — December 13, 2009 @ 12:07 am

  7. After reading this article and learning about the first two states, I wanted to learn more about the third, particularly pertaining to oxytocin. Oxytocin is nicknamed the “cuddle chemical”, due to the happiness “high” that one gets when the hypothalamus pumps it out. In a TIME magazine article, a study by Psychiatrist Rene Hurlemann of Bonn University and neuroscientist Keith Kendrick of the Cambridge Babraham Institute is discussed. The study tested if oxytocin could be artificially administered to manipulate emotions of empathy. Half the group received an aerosol shot of oxytocin while the other half received a placebo. The results showed that the group with the oxytocin shot showed more empathy and was more considerate of others’ feelings. This study may explain how you state that oxytocin produces a stable attachment in a relationship. When one is more conscious of their partner’s feelings, a stronger bond between the two can form. Moreover, since oxytocin results in happier feelings, this is why we say that healthy relationships are happy ones.,8599,1986318,00.html

    Comment by John Lee — May 3, 2010 @ 10:02 pm

  8. A recent study entitled “The Neuropeptide Oxytocin Regulates Parochial Altruism in Intergroup Conflict Among Humans” ( based on experiments in which subjected distribute money led to the conclusion that doses of oxytocin make people more likely to favor the in-group at the expense of an out-group. “Oxytocin creates intergroup bias primarily because it motivates in-group favoritism and because it motivates out-group derogation,” says Dr. De Dreu,

    Now bringing this back to this blog post. If the chemicals and sentiments involved in love are comparable to those of OCD, and on top of this when one is flooded with oxytocin due to “love” (assuming that this is part of the definition of love, i must also question what the experiments define as “love” (,8599,1986318,00.html) does this mean that not only is the person very “obsessed” with their partner, but also less attracted toward others as a result?
    And this leads me to question what the evolutionary benefit of becoming “obsessively” attached to a partner and simultaneously detached from others could mean, and what are its implications in current day society?

    Comment by Lucia — May 6, 2012 @ 4:07 pm

  9. Thinking about love as an obsession compulsion makes a lot of sense to me after reading this article. I’ve known plenty of people who claimed to be madly in love with someone one day and then seems to forget about that same person a month later. They seem to be crazy about the idea of love rather than an actual person that they claim to love. I really enjoyed the part of this article about romance, and how it can be explained as our search for a partner who will be there to help raise offspring, as a lifelong goal. I’m glad that there’s lots of information out there about the chemical reactions explaining what causes love and what causes people to fall in love, but I personally like thinking about it as the pursuit for a lifelong partner who will help raise offspring much more. It makes love sound like a noble cause dedicated to something bigger than ourselves, rather than just chemical reactions.

    Comment by Artie Blissert — December 19, 2014 @ 10:08 am

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