Nerina Ramlakhan remembers when her daughter was a toddler, and how if she got too tired she would be unable to switch off. “There was a healthy level of tiredness,” she says. “But if she went beyond that, she would be running on a kind of false energy. And then she wouldn’t be able to switch off when she went to bed.”

Overtiredness is recognised the world over in young children – but it is seemingly more and more common in adults. Dr Ramlakhan should know: she is a sleep psychologist and is increasingly seeing people who remind her of her little girl when she was younger.

There’s certainly an irony that in our sophisticated, hi-tech, busy world we appear to be reverting to behaviour that we recognise and know how to treat in kids, but are somehow failing to deal with as adults. Overtiredness, sleep experts agree, is down to our always-on existence. In the past, says Ramlakhan, the author of The Little Book of Sleep, our days had naturally built-in downtime that gave us short snatches of rest. Today, that has disappeared for many of us. “We have become restless as a society – and that places more demands on us when we get into bed at night,” she says. “We have lost the rituals and practices that gave us little respites during the day. In the past, you would go to the supermarket and, while you were waiting in the queue, you’d daydream, be a bit bored, look around. Now, any window like that will be filled by looking at your phone, answering some emails, sorting out your Amazon account.”

You may think you are putting the time to good use – but that’s not how your brain interprets it. There’s a complex neurophysiology that requires breaks in tasks and concentration; if it’s constantly bombarded, the brain becomes overloaded. The result, says Ramlakhan, is that it goes into what we might call survival mode: it assumes that something bad is about to happen, it ups the adrenaline and it puts out an urgent call for sugary snacks to provide quick-release energy.

And there’s more: if your brain has become tuned to always reaching for the next thing to do, to never taking a moment to just pause and rest, then it will gradually become harder and harder to switch off at night. It’s almost as if we’re losing the ability to let go; and the biggest letting-go of all is falling asleep, which Ramlakhan describes as an act of trust. “There’s a growing tendency to hold on, to keep on going, and it’s manifesting in our sleep patterns as well. People say to me that they feel they’re on the edge of sleep all night. They’re getting up in the morning feeling exhausted. They say they keep waking up at night and can’t get back to sleep. But it’s normal to wake up at night; most of the time, we just go back to sleep.”

What are the signs that you may be overtired? If you get into bed at night and find your mind is still racing with what has been going on through the day, overtiredness could be to blame. During the day, you may find it difficult to concentrate or to see the wood for the trees in your professional and your personal lives. You perhaps catch a lot of colds, especially when you’re winding down for a holiday. You’re irritable and you find yourself reaching for sugary snacks to keep yourself going during the day.

Overtiredness is easy to spot in young people. Photograph: Yasser Chalid/Getty Images

Vik Veer is an ear, nose and throat consultant who specialises in sleep apnoea. But he has become something of a sleep expert because so many people who consult him turn out to have different sleep issues, including – he believes – overtiredness. “It’s about struggling to survive on less sleep than you really need,” he says. “We’re talking about people who typically have coffee in the morning to wake themselves up and then alcohol in the evening to try to switch themselves off for sleep. They’re those people who seem to just about get by – because if you do it enough, your body habituates to it. You see people looking haggard and tired, and only just making it through.”

Who is at particular risk of overtiredness? Veer says thirty- and fortysomethings are especially vulnerable: they often have a great deal on their plates and they feel they have to keep on going, however tough the terrain. They are less likely than older people to build breaks and switch-off time into their days; they have high expectations of their social life as well as their professional life, so a busy day at the office is followed by a busy evening out in a bar or meeting friends.

Even when they fall into bed at night, they remember that TV programme everyone is talking about, which they didn’t have time to see when it was on the telly. So, they decide to spend another hour watching the first of the box set; and then a second; and before they turn out the light, they reach again for their phone for a quick update on messages and news.

No wonder it has all gone pear-shaped for sleep: what we are doing, says the consultant clinical psychologist Dr Anna Symonds, who works in Nottinghamshire, is inverting Maslow’s hierarchy of needs. In 1943, the American psychologist put physiological requirements, including sleep, food, water and shelter, at the bottom of his pyramid; self-actualisation, such as seeking happiness, pursuing a goal, using our talents, are at the top. Today, we are inverting the triangle: we prioritise the top elements and skimp on what’s lower down. As it is harder to go without food, water and shelter, we have decided sleep is expendable.

But it’s not – and overtiredness is one of the signs that we are getting it wrong. Paradoxically, another society-wide symptom, says Ramlakhan, is our communal obsession with sleep. “We’re sleeping in better conditions than ever before; we know more about it than ever before; we have better duvets, more comfortable pillows,” she says. So, it’s not the mechanics of sleep that are failing us; it’s our inability to pace our day and to understand that some of the business of rest at night is actually done during the day – and especially during the evening.

How do we banish overtiredness? Symonds says we need to look at how we deal with the condition in kids and put the same wisdom to use in our own lives. “We’re good at knowing we should limit screen time for our children, but not so good with ourselves,” she says. Veer recommends sleep hygiene techniques, especially cutting out coffee in the second half of the day and having a wind-down routine, just as children do. Ramlakhan says we should also drink more water, get to bed earlier at least three nights a week – maybe as early as 9.30pm – and, crucially, cultivate a rather more healthy relationship with our technology.

We are, after all, mere toddlers in the digital world; like little kids who don’t know when they have had enough chocolate. We haven’t learned as a society when to say no to being “always on” – and overtiredness is one of the many consequences.