It’s true — kiss and make up before bed really is good for you

For once, the old wives with their tales and rules were right. Don’t get me wrong: most of it is nonsense. Tomato sauce will not put hairs on your chest; a mirror is simply a reflective surface and breaking it will not catalyse a cascade of misfortune for seven years; trees do not grow in your stomach if you eat apple pips (It took me years to stop believing in that one).

But “don’t go to bed angry” — standard advice for newlyweds as well as exhausted instructions from a mother to warring children — contains seeds of truth.

A team of Chinese and US researchers has investigated what happens in your brain when you fixate on negative thoughts and emotions, before falling asleep with them roiling in your head. Their findings were published this week in the scientific journal Nature Communications.

“This study suggests that there is certain merit in this age-old advice: ‘Do not go to bed angry’,” co-author Yunzhe Liu, who conducted the research at Beijing Normal University in China, said. “We would suggest to first resolve [an] argument before bed.”

It makes sense in retrospect: we already knew that sleep is fundamental in consolidating memories. It is one of the main things that teachers tell students ahead of exams, that it is better to get a good night’s sleep than try to cram information that you will invariably forget.

Liu and the other researchers took 73 male university students and trained them to create adverse memories. This is not as Clockwork Orange as it sounds: they were made to link pictures of faces with negative scenes or images. The images were rather gruesome, though: mutilated bodies, crying children; that sort of thing.

They were asked to do one of two things when shown the face picture as a prompt: actively remember the scene or image, or purposefully forget it.

For half of the participants, this happened 30 minutes after they had learnt the association (or, as the authors of the study call it, “a newly acquired condition”); the other half performed this recall the next day (that is, “overnight consolidation condition”).

During this acquisition and recall, the students were attached to functional magnetic resonance imaging (fMRI), which allows researchers to see events in the brain by tracking where the blood is flowing.

The students who slept on it were more likely to remember the traumatic image, and the memory itself had consolidated itself in their brains.

In the quick-recall group, their hippocampus, thought to be the hub of memory and learning, was lighting up like a Christmas tree.

For the overnight folks, this activity had diffused through the cortex, implying that the memory was more entrenched.

This sort of research extends beyond old wives’ tales and domestic disputes — it helps to shed light on mental health issues such as post-traumatic stress disorder. Bad memories, according to the researchers, are likely to

SLEEP SEEMS TO CONSOLIDATE AVERSIVE MEMORIES, GIVING RISE TO THERAPIES

linger longer than positive ones, and they are more difficult to suppress.

But sleep seems to consolidate aversive memories, which gives rise to possible therapies, such as sleep deprivation.

There is an important flaw in the study, which surprisingly is not mentioned in the discussion section of the paper.

The study was only done on men, and there are marked differences between the brains of men and women. Even in the womb, the XY chromosome in male babies (women have XX) creates a genetic cascade that affects the development of the brain.

So, perhaps this science-backed old wives’ wisdom needs a qualifier: men should not go to bed on an argument. For women, we are not sure yet.