If you want to know if he loves you so, a new study suggests that the secret may not be in his kiss, but in his far less romantic-sounding blood levels of oxytocin.
According to the study, published in Psychoneuroendocrinology, higher levels of oxytocin — the hormone known as the “cuddle chemical,” which rises during breast-feeding, lovemaking and parent-child bonding — were associated with more emotional responsiveness between couples and predicted which couples would stay together longer than others.
The study involved 163 adults in their 20s. Of the participants, 120 were new couples who had just started a romantic relationship; the rest were singles. Researchers found that people in the throes of new love had far higher levels of oxytocin than the unpartnered did. And higher oxytocin levels were linked with more affectionate touch, better moods and greater synchrony of movements between couples.
What’s more, couples with the highest levels of the hormone early on were more likely to stay together, compared with those with lower levels — at least based on the 25 couples who were still together and with whom the researchers were able to follow up six months later.
MORE: ‘Love Hormone’ Oxytocin Is Choosy, But Not Necessarily Racist
But oxytocin isn’t all cuddles and coos: higher levels were also associated with more anxiety and obsessiveness about the relationship — a finding that also applies to new parents (in their case, they obsess and worry about their children). The researchers suggest, however, that that might not necessarily be a bad thing. “The current findings may suggest that preoccupations with the romantic partner and the relationship are just as essential for the formation of the selective and enduring romantic bond,” they write.
However, the study couldn’t determine whether people who began with higher levels of oxytocin were more likely to fall in love and stay coupled — or whether good loving itself increased oxytocin and kept the lovers linked.
The authors write that the connection could result from a “feedback loop whereby higher levels of reciprocity and touch increased the couples involvement in the relationship at the physiological, behavioral and representational levels.” In other words, romantic words, thoughts and behavior might raise oxytocin levels and lead to increased affection and connection, which leads to more oxytocin and so on.
In practical terms, this means that if you want to stay in love, acting like you’re in love may be the best way to do it. One prior study does suggest that taking oxytocin itself can improve communication and relieve stress when couples fight — but since it can also increase anxiety and obsessiveness, it’s not clear whether giving it as a drug rather than a hug also has the potential to do harm in some situations.
MORE: Should the ‘Love Hormone’ Oxytocin Be Used in Couples Therapy?
Interestingly, it was love rather than sex that the study found to be connected with oxytocin. While prior research has found that oxytocin levels rise at orgasm, this study found that new couples had higher oxytocin levels than singles, regardless of whether they had consummated the relationship.
Also, although research by the same authors has found elevated levels of oxytocin in new parents, compared with singles, they write, “levels at the initial stages of romantic attachment were significantly higher in new lovers than those observed in new parents, indicating that the initial period of romantic love may induce the most intense activity of the oxytocinergic system.” More research is needed to confirm this finding, however.
Meanwhile, perhaps it’s the fact that new love and early parenthood are chemically similar that helps explain — but doesn’t necessarily excuse — why new couples often become annoyingly cute and call each other infantile names.
MAGAZINE: Early Decision: Will Prenatal Testing Shrink the Ranks of Babies with Down Syndrome?
Maia Szalavitz is a health writer for TIME.com. Find her on Twitter at @maiasz. You can also continue the discussion on TIME Healthland’s Facebook page and on Twitter at @TIMEHealthland.