Why It Hurts To Be Separated From a Loved One In a study published last autumn, researchers showed that male prairie voles that had been separated from their female partners for four days exhibited depression-like behaviour. This is a much shorter amount of separation time than researchers had previously found to affect the voles’ physiology. They also had increased levels of corticosterone, the rodent equivalent of the human stress hormone cortisol. Male prairie voles that had been separated from their male ‘brothers’ did not display any of these symptoms. This implied that the response was tied specifically to separation from their mates, rather than just social isolation. When the animals received a drug that blocked corticosterone release, they no longer showed depression-like behaviour following separation from their partners, confirming that stress hormones were at the root of the response. In many ways, separation appears to resemble drug withdrawal. Studies have shown that in monogamous animals, cohabiting and mating increase levels of oxytocin and vasopressin—hormones that foster emotional attachments—and activate brain areas associated with reward. As a result, when prairie voles are separated from their partners even for a short time, they experience withdrawal-like symptoms. It is as if  this mechanism creates a certain state so that the animals want to seek out their partner to hold that bond together. In a recent study of human couples, social psychologist Lisa Diamond of the University of Utah observed minor withdrawal-like symptoms, such as irritability and sleep disturbances, along with an increase in cortisol in subjects after they were separated four to seven days. Participants who reported high anxiety about their relationships had the biggest spikes in cortisol levels. However even those who reported low levels of stress and anxiety during the separation exhibited some degree of increased cortisol and physical discomfort. These results, like those from the prairie vole study, indicate a specific link between separation and increased cortisol, implying cortisol-blocking drugs may benefit people struggling to cope with partner separation, too. Researchers believe the pair bond evolved from the parent-child bond, which may explain why we feel romantic attachments so strongly. The same neurochemicals—oxytocin, vasopressin and dopamine—have been implicated in both relationships. The behavioural patterns associated with parental and romantic bond formation and separation are also similar. There are future studies about romantic attachment planned that will focus on using these findings to develop new treatments for grief associated with partner separation or loss, as well as for disorders that involve social deficits, such as schizophrenia and autism. References: E. Westly. Separation Anxiety for Adults. Scientific American Mind, February 2009. H.E. Ross, S.M. Freeman, L.L. Spiegel, X. Ren, E.F. Terwilliger, L.J. Young. Variation in oxytocin receptor density in the nucleus accumbens has differential effects on affiliative behaviors in monogamous and polygamous voles. J Neurosci. 2009 Feb 4;29(5):1312-8.