A new research has found that couples who slept together had enhanced and less disrupted rapid-eye movement (REM) sleep compared to when they slept individually.
The REM sleep is associated with vivid dreams and has been linked to emotion regulation, memory consolidation, social interactions and creative problem solving.
"Sleeping with a partner might actually give you an extra boost regarding your mental health, your memory and creative problem-solving skills," said Dr Henning Johannes Drews of the Center for Integrative Psychiatry (ZIP), Germany.
To date, most studies have compared co-sleep to individual sleep in couples by only measuring body movements.
However Dr Drews and colleagues overcame these limitations by also assessing sleep architecture in couples that shared a bed.
They measured sleep parameters both in the presence and absence of the partner using dual simultaneous polysomnography, which is a "very exact, detailed and comprehensive method to capture sleep on many levels -- from brain waves to movements, respiration, muscle tension, movements, heart activity".
Additionally, the participants completed questionnaires designed to measure relationship characteristics (relationship duration, degree of passionate love and relationship depth, etc.)
The team found that couples synchronize their sleep patterns when sleeping together.
This synchronization, which is not linked to the fact that partners disturb each other during the night, is positively associated with relationship depth.
In order words, the higher participants rated the significance of their relationship to their life, the stronger the synchronization with their partner.
Interestingly, researchers found an increased limb movement in couples who share the bed.
However, these movements do not disrupt sleep architecture, which remains unaltered.
"One could say that while your body is a bit unrulier when sleeping with somebody, your brain is not," said Drews.
Although results are promising, some questions remain to be answered.
"The first thing that is important to be assessed in the future is whether the partner-effects we found (promoted REM sleep during co-sleep) are also present in a more diverse sample (elderly, or if one partner suffers from a disease)," the authors wrote in the paper published in the open-access journal Frontiers.
The research furthers our understanding of sleep in couples and its potential implication for mental health, they added.