Loneliness is everywhere in the world of psychology these days – the subject of so many studies, articles and talks that you sometimes wish the loneliness researchers would go away, so you could just get some damn time to yourself. Perhaps you knew that loneliness can be lethal: it’s linked to heart disease, insomnia and depression, and is a better predictor than obesity of an early death.
But the new spin on loneliness is that we ought to welcome it, in modest doses. “As long as we then do what we should do – reconnect with people – then loneliness is a good thing,” the German psychologist Maike Luhmann told the US website Vox. “This is a sign from our psychological systems that there’s something off.” 
It’s a “biological warning system” that evolved over millennia, alerting us to potentially dangerous levels of isolation. True, isolation isn’t so dangerous today: a friendless Londoner is less likely to starve, or be eaten, than a friendless prehistoric hunter-gatherer. But there’s a reason the pang of loneliness hurts so much.
This notion gets greeted with surprise – loneliness, a good thing? – but the surprising thing is that we ever imagined otherwise. Why would we have developed this response to isolation if it didn’t serve some purpose? (As the psychology writer Melissa Dahl points out, the same can be said for boredom, a warning that you need more meaning in your life, and for anxiety, which helps prepare for potential threats.) 
This becomes obvious if you consider physical pain. A throbbing ache in your abdomen isn’t pleasant, but it’s a “good thing” if it prompts you to head to the doctor’s and address whatever’s causing it. In programming parlance, pain isn’t a bug; it’s a feature.
If we tend to resist thinking about emotions in this way – as warning bells – that’s probably because it sounds like dispensing blame. Telling lonely people they ought to get out more seems to imply it’s their fault they’re lonely. 
Likewise, some forms of depression are a rational response to a bad situation you need to address: maybe it’s time to leave a relationship, or confront an inner conflict. But we’d rather not hear that; blaming a “chemical imbalance” seems less daunting. We treat depression as the problem, when it’s often better thought of as a symptom.
The nasty twist in this is that loneliness, like depression, can turn chronic. A vicious circle begins. You come to see your surroundings as hostile – they’re making you feel bad, after all – so you respond to others in unfriendly ways, or avoid contact altogether. (That’s your early warning system on the blink: in Paleolithic times, it might have helped a highly isolated person to be hyper-alert to threats, but not any more.) 
This kind of loneliness demands a skilful response: you need to heed the warning bell, while not heeding the thoughts to which it gives rise, telling you to pull away. Reach out, even if it feels unappealing. 
Once again, the analogy with physical pain is helpful. Surgery’s rarely appealing, either, but sometimes it’s exactly what you need. – Guardian News and Media