“If you’ve ever tried not to think about something, you know how impossible that task is,” Karlstedt adds. “To know what not to think about, our brain has to think about it. This means that with ruminating thoughts, if we try not to think about them, we accidentally think about them more, thus keeping the spiral going.”

So why does this repetitive spiral of worry tend to come into its own at the very time we’re trying to switch off? “Many people find that rumination is more likely to kick in for them around bedtime in part because this is often the time when we have less external stimuli to keep us distracted from our own internal experiences and thoughts,” Karlstedt explains. During the day, we might be able to keep negative thoughts and regrets at bay by keeping busy with other tasks or by discussing our fears with other people, but that’s not usually an option at 1am.

Once we’ve started grappling with those unpleasant thoughts, our body starts to react – often in a way that couldn’t be less favourable for sleep. “Because rumination is a form of anxiety, when we begin to engage with it, our body begins to undergo the physiological changes associated with a fight or flight response,” Karlstedt says. Think adrenaline rushes and an increase in blood pressure and heart rate. “In other words,” she adds, “we get more alert and prepared to take action – not exactly the most conducive state for falling asleep.”

Why rumination is keeping you up at night – and how to beat it for better sleep