A study has found that romantic people have a genetic mutation that produces more of the ‘cuddle hormone’ oxytocin – which makes them more likely to fall in love.

The genetic mutation boosts the mood and ability of more romantic people, urging them to form relationships, according to researchers from McGill University, Quebec.

For their research the team focused on a gene called CD38 which fuels oxytocin and found those with two copies were more affectionate. 

Those that have this genetic mutation are also more likely to spend a greater amount of time eating, drinking, talking and watching TV than those without the gene.


It isn’t just the people with the mutation that it affects – researchers found that from a study of 111 couples those with the mutation also found their partner more caring even if they did not have two copies of the gene. 

They were also more likely to overlook mistakes, swallow pride and give in to requests – known as ‘relationship adjustment’, according to researchers. 

It is the first time the gene has been associated with human romantic behaviour in daily life, according to lead author Professor Jennifer Bartz. 

‘Variations may play a key role in behaviours and perceptions that support bonding in humans,’ Bartz explained.

Her team tracked 111 couples who had been together for an average of five or six years and got them to report their social behaviours and their perception of their partner’s social behaviour for a period of 20 days.

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Out of the 222 individuals taking part in the study – 118 also provided genetic information – that worked out as 65 women and 53 men.

The CD38 gene has two variants, or ‘alleles’ – A and C. Every person has two copies – one inherited from each parent.

Alleles are forms of the same gene with small differences in their sequence of DNA bases. So the gene can be present in three combinations – AA, CC and AC.

Volunteers who inherited a double dose of the ‘genotype’ CC reported higher ‘communal behaviour’ than carriers of AA or AC.

They were also more likely to see their partner acting the same way even if their partner didn’t have the same genetic codes.

Those with the genetic variant also experienced fewer negative feelings such as worry, frustration or anger than their peers.

They also rated the quality of their relationship as better – and more supportive.

Professor Bartz said: ‘Given the significance of close relationships for human survival, it is thought biological mechanisms evolved to support their initiation and maintenance.

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‘Individuals with the CC allele reported higher levels of communal behaviour across their daily interactions with their romantic partner.

‘They also had higher levels of relationship adjustment.’ 

She added: ‘These findings support the role of oxytocin in the interpersonal processes implicated in the maintenance of close relationships.’ 

They add to increasing evidence genetic factors play a role in the formation of relationships, and dating websites have been launched to combine genetics and matchmaking. 

Studies have shown identical twins, raised separately, rate the overall quality of their marriages similarly. This suggests an enduring genetic contribution to marital life.  

Oxytocin, also known as the ‘love hormone’, plays a significant role in emotional attachment – flooding a new mother at the birth of a child and spiking during sex. 

Professor Bartz said decades of research on mice rodents and the socially monogamous prairie vole indicates oxytocin boosts romantic bonding.

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She added: ‘We demonstrate, for the first time, that CD38, a gene linked to oxytocin secretion and social behaviour in rodents, is also involved in regulating human romantic relationships as they unfold in daily life.

‘Specifically, we show it is associated with an individual’s communal behaviour, such as the expression of affection in daily interactions with a romantic partner.’

The study was published in the journal Scientific Reports.