Everyone knows it’s no fun to be away from your significant other. Studies using anecdotal evidence have indicated that long-term separation from a romantic partner can lead to increased anxiety and depression as well as problems such as sleep disturbances. Now researchers are identifying the neurochemical mechanisms behind these behavioral and physiological effects.

In a study published last fall, researchers showed that male prairie voles that had been separated from their female partners for four days—a much shorter amount of separation time than researchers had previously found to affect the voles’ physiology—exhibited depressionlike behavior and had increased levels of corticosterone, the rodent equivalent of the human stress hormone cortisol. Males that had been separated from their male siblings did not display any of these symptoms, implying the response was tied specific­ally to mate separation, not just social isolation. When the animals received a drug that blocked cortico­sterone re­lease, they no longer exhibited depres­sionlike behavior following partner sep­aration, 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, says Larry Young, a behavioral neuroscientist at Emory University’s Yerkes National Primate Research Center and co-author of the study. “In the short term, I think [this mechanism] creates an aversive state so that the animals want to seek out their partner to hold that bond together,” Young says.

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, but 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 Young’s 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, and the be­havioral patterns associated with parental and romantic bond formation and sepa­ration are also similar. “We think about parent-child relationships and adult ro­man­tic relationships as being funda­mentally different,” Diamond explains, “but it really boils down to the same functional purpose: creating a psycho­logical drive to be near the other person, to want to take care of them, and being resistant to being separated from them.”

Future studies about romantic attachment will focus on using the findings from research such as Young’s and Diamond’s to develop new treatments for grief associated with partner separation or loss and for disorders that involve social deficits, such as schizophrenia and autism.

Note: This article was originally printed with the title, "Separation Anxiety for Adults".