Oxytocin- the love hormone or the hate hormone?

Oxytocin- the love chemical by MAMR2009 Fliqr

Oxytocin is a hormone and neurotransmitter that is produced in the hypothalamus, and is transported to the pituitary gland at the base of the brain. It is deemed the ‘love hormone’ as its levels increase when showing affection and love. It also plays a role in social bonding, sexual reproduction, empathy, relationships, childbirth and breastfeeding. Individuals at the start of romantic relationships also have higher levels of oxytocin compared with non-attached single individuals. So should we just start popping oxytocin pills? Not so fast. Oxytocin may not be all it’s cracked up to be…

What are the behavioural effects?

Research conducted in 2011 has shown that delivering oxytocin through a nasal spray led to improved self-perception, and an increase in personality traits such as warmth, altruism, trust and openness. A follow up study published by PNAS in 2013 showed that doses of oxytocin may be able to help keep men faithful to their wives. So why don’t we all just take doses of oxytocin?

Linking Brains by redcoulter Fliqr

It may be a more complicated story than we first thought. Before you shop online for a bottle of the “love” hormone to improve social relationships let’s analyse the negative effects of oxytocin, and possible positive effects when it’s blocked. Behavioural scientist Natalia Duque-Wilckens conducted a study that showed that after negative social situations, oxytocin promotes avoiding social situations the brain isn’t familiar with. Duque-Wilckens worked with mice which, when stressed, would avoid other mice rather than approaching them. If the stressed mice were given a drug which blocked the activity of oxytocin normal behaviour would be restored. These findings supported a theory that Duque-Williams had, that oxytocin is used in the brain to amplify the effect of social experience whether they be positive or negative. In a positive context, they do amplify positive social emotions (hence “love” hormone) but in a negative social context (fighting, bullying) the hormone could promote social avoidance and isolation. It has also been reported that oxytocin can have a positive or negative effect depending on how the subjects view their relationships to other people.

 

How could the same hormone have such different effects?

Two different regions in the brain respond differently depending on the social situation. In a positive social context, the nucleus accumbens, a region of the brain important for reward and motivation, is stimulated. In a negative social context the bed nucleus of the stria terminalis (BNST), a region known to regulate anxiety, is stimulated.

Coloured Brain by Lea Wikimedia commons

Oxytocin has a more nuanced role in social interactions than previously thought, and varies from person to person and situation to situation. It isn’t an all-purpose attachment remedy. Despite its positive effects on the body and social relationships, it isn’t ready to become a go-to drug to fix depression and social issues.

What are the effects in dogs?

Oxytocin is a social hormone in many species, not just humans. According to research by Evan MacLean at the University of Arizona, oxytocin has an important role to play in shaping dogs’ behaviour. Thousands of people are hospitalised every year for dog bites, so understanding and preventing dog aggression is important. Oxytocin in dogs seems not to have the negative side it has in humans. Dogs which are specifically bred to have non-aggressive temperaments when compared to levels of regular pet dogs are found to have much higher levels of oxytocin. According to MacLean, “high oxytocin levels in assistance dogs are completely consistent with their behavioural phenotype- that they’re very, very friendly dogs that are not aggressive towards people or other dogs”.

It is clear than oxytocin has many roles, and “love hormone” could be a misleading name.