Alone in a crowd (Image: Lauri Rotko/Getty)

In recent decades, social isolation has been recognised as a major risk to our health and longevity. It’s twice as bad for you as being obese and nearly as bad as smoking. The rising number of people who say they are affected, across a wide range of ages, is startling. Yet obvious mechanisms – such as self-neglect – do not explain the full health toll. So what else is going on?

To answer this question it is worth noting that you can suffer the ill effects of loneliness even if you are not socially isolated. It is essentially an emotional state, and recognising the brain’s role is vital to understanding much of the harm that can be caused.

Comedian Robin Williams made a salient observation in 2009: “I used to think the worst thing in life was to end up all alone. It’s not. The worst thing in life is to end up with people who make you feel all alone.” Tracking large groups over time indicates that perceived social isolation carries its own risk for morbidity and mortality, independent of actual social isolation. What could drive this surprising effect?


Safety in numbers

The perception of isolation from others – of being on the social perimeter – is not only a cause of unhappiness, it also signals danger. Fish have evolved to swim to the middle of their group when predators approach, mice housed in social isolation show sleep disruptions and reduced slow-wave sleep and prairie voles isolated from their partners then placed in an open field explore their surroundings less and concentrate on predator evasion.

These behaviours reflect an increased emphasis on self-preservation when on the social perimeter. For instance, fish on the edge of a school are more likely to be attacked by predators because they are easier to isolate and prey upon. Such observations reflect a more general principle, that perceived social isolation in social animals activates neural, neuroendocrine and behavioural responses that promote short-term self-preservation. However, these responses bring a cost for long-term health and well-being.

The range of harmful neural and behavioural effects of perceived isolation documented in adults include increased anxiety, hostility and social withdrawal; fragmented sleep and daytime fatigue; increased vascular resistance and altered gene expression and immunity; decreased impulse control; increased negativity and depressive symptoms; and increased age-related cognitive decline and risk of dementia.

A little less lonesome

Sadly, to date, attempts to reduce loneliness have met with limited success. A meta-analysis of different strategies studied in randomised controlled trials, showed they had only a small effect. Among the four types of interventions examined, talking therapy that focused on inappropriate thought processes – a lack of self-worth, a lack of perspective and a skewed idea of how trustworthy others are and how they perceive you – had the largest impact. Social skills training, social support and increased opportunities for social contact were much less effective.

This finding is consistent with the idea that perceived social isolation can still put us in self-preservation mode – a hangover from ancient times when isolation would have left us very vulnerable to attack – which can lead to harmful thought processes and behaviour that is at odds with thriving in a modern society.

There is no pharmacological treatment for loneliness, although animal research is shedding light on this possibility. Given the scale of the problem today, the hunt for better treatments of all types deserves high priority.