By Emily Reynolds

Though some research has challenged the common conception that scent is the most evocative of all the senses, it can be undeniably powerful when you catch a whiff of something that jogs a memory. We also know that scent plays a part in sexual attraction: people with a keener sense of smell often find sex more pleasant and may even have more orgasms during sex, and the scent of a partner can reduce stress and increase feelings of safety.

So new research findings from a team at the University of British Columbia may not come as a complete surprise. In a paper published in Psychological Science, Marlise Hofer and Frances Chen suggest that the scent of your lover may not just be comforting but can also help you drift off to sleep.

The team asked 155 heterosexual participants in long-term romantic relationships to sleep with a t-shirt for a pillowcase on two separate nights. One of these shirts had previously been worn for 24 hours by their romantic partner, and the other was a control shirt, which had either not been worn, or worn by a “scent donor” unknown to participants. T-shirt wearers were asked to refrain from using any scented body products and to avoid activities likely to produce odours such as exercise, smoking, sex or eating pungent foods.

Each night, participants’ “sleep efficiency” — i.e. the proportion of time they spent in bed that they were actually asleep — was measured via a smartwatch Then, in the morning, participants were asked what time they went to bed and got up, how they would rate their sleep quality, how well rested they felt, and whether or not they believed the scent was their partner’s or the control.

As expected, sleep efficiency was higher on nights spent sleeping with a partner’s shirt rather than with a control shirt — and this was still the case when controlling for multiple factors, including participants’ relationship quality and length, attachment style and levels of stress. Efficiency was increased by an average of 2.1% — around the same increase induced by melatonin supplements, often used to improve sleep. And though participants were able to identify their partner’s scent 70% of the time, the results also suggested that sleep efficiency improved whether or not participants were aware that the t-shirt was their partner’s.

When it came to sleep quality, however, participants only reported having higher quality sleep when they believed they were spending the night with their partner’s shirt, whether or not they were actually exposed to their smell.

Individual differences, the team notes, are likely to moderate these effects, something the study did not explore in depth. Women, for example, were more likely to see an increase in sleep efficiency than men, and factors like relationship quality are likely to have a variety of impacts on both quality and efficiency of sleep.

But for anyone who’s ever struggled to drift off when alone, the results are still cheering. Melatonin is all well and good — but a worn t-shirt could be the real secret to getting a good night’s sleep.

– The Scent of a Good Night’s Sleep: Olfactory Cues of a Romantic Partner Improve Sleep Efficiency

Emily Reynolds (@rey_z) is a staff writer at BPS Research Digest