Amber Minogue

The study was based on sleep and mood data gathered by experts at the University of Michigan's Academic Medical Center, using a combination of wearable tech and symptom questionnaires.

According to the official media release, the study participants were all medical interns, which means they often experienced the long intense work days and irregular work schedules that are the hallmark of this time in medical training.

Still, a pattern emerged demonstrating that those with the most variable sleep schedules were more likely to score higher on a depression questionnaire and to have a lower mood rating.

It's somewhat similar to the phenomenon known as social jet lag.

You mean like jet lag from flying?

Well, exactly.

The term was coined because it's a similar feeling to when you're jet lagged after a long-haul flight.

Regular listeners will know that our bodies have circadian rhythms which are 24-hour cycles that are part of our body's internal clock and they don't really like being thrown off.

Changing your usual bedtime or wake-up time puts stress on your body which thrives on consistency.

In an article on weekend lie-ins, sleepstation.org.uk cites changes in core body temperature, fluctuations in melatonin and variation in levels of human growth hormone as some of the chemical and physical changes that regulate our sleep and sleepiness each day.

The article also explains that we ideally want to wake up naturally at a time when the hormones that encourage wakefulness, like adrenocorticotropin and cortisol, are at their highest, and by the same logic go to sleep when melatonin and adenosine concentrations are raised in the body.

Of course, we don't intentionally disrupt our circadian rhythms, but it's inevitable that it happens from time to time when we have a night out on a weekend or stay up late watching TV because we know we don't have to go to work the next day.

Even getting an early night on a Sunday can be problematic if it doesn't match your regular schedule.

What's the best way to make up for lost sleep then?

Well, really, you want to get enough sleep during the week so you don't need to catch up to start with.

We all have different sleep patterns, but our basic need for sleep remains pretty consistent throughout life.

Short sleepers tend to stay short sleepers and long sleepers stay long sleepers.

Why does not getting enough sleep make you selfish?

Thanks for asking.

Not getting a good night's sleep can certainly leave you feeling grumpy and groggy, but can it also make you selfish?