It’s even been suggested as a major reason why people in close relationships tend to be in better health and live longer.
Researchers from the University of Pittsburgh in the U.S. believe sleeping next to someone helps lower the stress hormone cortisol, perhaps because it encourages feelings of safety and security.
Prolonged periods of elevated cortisol have been linked with an increase in cytokines — proteins involved in inflammation that can trigger heart disease, depression and autoimmune disorders.
Sleeping together has a protective effect by lowering the levels of these proteins.
“Sleep is a critically important health behaviour that we know is associated with heart disease and psychiatric wellbeing,” the Daily Mail quoted lead researcher Wendy Troxel, assistant professor of psychiatry and psychology at the university, as saying.
“There is extensive literature showing that married people — happily married people, in particular — live longer, happier, and healthier lives than their unmarried or unhappily married counterparts.
“We also know sleep is critically important for health and wellbeing, and it happens to be a behaviour couples engage in together, so it stands to reason it may be an important link with their health,” Troxel added.
Sharing a bed is also thought to boost levels of the ‘love hormone’ oxytocin, known to induce bonding feelings.
This is traditionally thought to be released during sex, but Dr David Hamilton, a scientist who has examined the role of oxytocin in health in his book, Why Kindness Is Good For You, says it’s also associated with cuddling in bed and ‘pillow talk’.
Recent studies have shown oxytocin’s vital role in health. Scientists at Malmo University Hospital in Sweden found it can affect digestion.
Those with lower levels had poorer gastric motility — the process by which food is moved from the stomach to the intestines, therefore slowing down digestion.
Levels of the hormone have been found to be lower in patients with irritable bowel syndrome, said Dr Hamilton.
Oxytocin has also been shown to reduce inflammation and a number of recent studies have revealed how the hormone can affect the heart, said Dr Hamilton.
For example, a study from the University of North Carolina asked 59 women who were married or had partners to keep a diary of the number of hugs they received over a set time.
The scientists then analysed levels of oxytocin in the blood. The women who’d received the most hugs had the highest levels of oxytocin — and the lowest blood pressure and heart rates.
It may come as a surprise to the long-suffering partners of snorers, teeth grinders and kickers, but sharing a bed may also improve your sleep.
In another of Dr Troxel’s studies, published in 2009, women in long-term stable relationships fell asleep more quickly and woke up less frequently during the night than single women or women who lost or gained a partner during the six to eight years of the study.
“Feelings of safety and security with a partner may lead to more restful sleep,” she said.