Couples who have been happily married for a long time often give the same piece of advice when it comes to relationship longevity: Don't go to bed angry. However, it's not just your love life that will suffer – new research suggests that going to bed in a bad mood can harm your sleep, too.

Now, seeing as poor sleep can negatively impact our health in all sorts of ways – from poor mental health to an increased risk of all sorts of long-term health problems – this latest discovery could provide an important insight into the ways in which we can improve our time spent between the sheets.

The study

Psychologists from Iowa State University monitored the sleep habits of 436 volunteers after they had completed questionnaires about their levels of anger. It was found that, generally speaking, the angrier a person was, the more their sleep suffered. Is has been hypothesised that this is because people who go to bed angry are more likely to stay awake and mull over issues in their head, rather than drift off peacefully. The report reads:

"Overall, individuals who had poor anger control also had worse objectively and subjectively measured sleep… The findings tie actual sleep behaviour to individual differences in anger, suggesting poor anger control plays the most important role, and add to the growing evidence that anger and sleep depend on each other."

The results remained the same even after adjustments were made to allow for differences in gender, age, race socioeconomic status and stress.

Considering the fact that previous research has suggested that a lack of sleep makes people more irritable and quick to anger, which in turn affects their ability to snooze – as suggested above – it's not unreasonable to suggest that many people are suffering from a self-perpetuated cycle of bad sleep.

If this sounds familiar to you, then it might be worth staying up that little bit later to try and get things resolved. Additionally, you could try these simple steps to improve your shut-eye.

Go to bed a little earlier – especially if you're tired.

– especially if you're tired. Don't rely on non-essential medication .

. Make sure your bedroom is a comfortable temperature (18-21C).

(18-21C). No screens before bed.

before bed. Avoid alcohol before bed time and ditch caffeine after 4pm.

before bed time and ditch caffeine after 4pm. Don't exercise too late at night.

too late at night. Make sure it's dark .

. Keep a sleep diary.

The study was published in the Journal of Research in Personality.

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