Counterpoint: Does the ‘Love Hormone’ Oxytocin Really Lead to True Love?

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Derived from the Greek phrase for ‘quick birth,’ oxytocin—initially discovered as a ‘contraction hormone’ in 1909 by physiologist Sir Henry H. Dale—has historically been touted as a miracle pregnancy hormone due to its efficient labor-inducing abilities. Produced in the hypothalamus and released into the bloodstream by the pituitary gland, oxytocin aids in both childbirth and postpartum lactation, and is commonly used by obstetricians and gynecologists.

In popular culture, however, oxytocin has been viewed quite differently. Through the influence of marketing strategies, oxytocin has become associated with the development of love. Commonly referred to as the ‘love hormone’ or ‘liquid trust,’ oxytocin products are sold by numerous companies that claim to have benefits for consumers’ outward trustworthiness and ability to form lasting, loving relationships. These claims were founded on numerous scientific studies conducted through the 1990s on prairie voles—a species of rodent known for their lifelong monogamous mating patterns. These studies suggested that the hormone played a significant role in the development of their mating relationships and parental behaviors.

Later studies from the 2000s and early 2010s also showed that oxytocin levels increase when people hug, experience gentle touch, or engage in consensual sexual interactions, while cortisol levels, associated with stress, decrease. Validated by these studies, oxytocin’s supposedly unmatched ability to promote love and bonding between people has been the main focus of ‘love hormone’ companies over the last twenty years. However, a recent study by Kristen Berendzen, Ruchira Sharma, and their colleagues at the University of California, San Francisco has uncovered inaccuracies and possible exaggerations in our understanding of this hormone.

In their paper published in Neuron in January, the researchers revealed that oxytocin may not be the determining factor in yielding mating and parental relationships in prairie voles. The researchers used CRISPR gene targeting technology, a gene editing tool capable of manipulating precise DNA sequences, to produce oxytocin receptor (Oxtr)-null prairie voles. These Oxtr null voles lacked function in their oxytocin receptors and were therefore unable to support oxytocin signaling. When these Oxtr null prairie voles were tested against control Oxtr prairie voles with intact oxytocin signaling abilities, the scientists found that the Oxtr null voles were still able to develop certain behaviors that previous studies had suggested were the result of oxytocin signaling in the brain.

Unexpectedly, even without the presence of oxytocin signaling, the Oxtr null prairie voles formed social attachments, mated normally, and presented typical parental behaviors. All of these behaviors were shown to have developed to the level—or mostly to the level, in a few cases—of those in control voles. Both male and female voles made mating connections and showed a preference for their mate over animals of the opposite sex. Female voles gave birth to healthy babies and nursed their pups to weaning, and parent voles displayed a similar intensive care for their children as regular voles did.

The study also revealed some variation in prairie vole behavior which may be attributed to the changes in oxytocin signaling induced by the researchers, even though the social behavior observed in Oxtr and Oxtr null voles was mostly the same. The most notable of these differences was that Oxtr null voles showed less aggression than regular voles towards voles of the opposite sex who were not their mate. In addition, Oxtr null female voles were found to produce litters with fewer surviving pups at weaning. These observations suggested that the importance of oxytocin in social attachment is much less than was previously believed.

Together, these findings indicate that oxytocin may play a different, more complex role in bonding, parenting, and social interaction than what was once believed. The groundbreaking results of this study, however, are not sufficient to fully understand the nuances of oxytocin and its properties. Subsequent oxytocin studies in a variety of species and populations will be necessary to decode this new mystery of the famous ‘love hormone.’ In any case, companies profiting from oxytocin product sales may have to find a new way to play on their consumers’ relationship insecurities—one that doesn’t involve their star hormone.