Loneliness, or lack of social contact, physically drains people of energy, a new study has found.

In an experiment conducted in a laboratory, as well as during COVID-19 lockdowns, “participants reported higher levels of tiredness after eight hours of social isolation”.

The results suggest that “low energy may be a basic human response to a lack of social contact”.

Like a hunger for food

The key finding, from the University of Vienna, is that a lack of social contact “induces a craving response in our brains comparable to hunger, which motivates us to reconnect”.

In other words, there are processes going on in our brain and hormones that signal we need to eat, via hunger pains.

Similarly there are processes that let us know we’ve been alone too long, and that we need to seek company.

This idea is known as the ‘social homeostasis’ hypothesis: That a dedicated homeostatic system autonomously regulates our need for social contact.

However, little is known about “how conditions of altered social homeostasis affect human psychology and physiology”. The experiment was designed to investigate this problem.

The experiment

Thirty female volunteers came into the lab (​in the university’s Department of Clinical and Health Psychology) on three separate days.

On these visits they spent eight hours without social contact or without food or with both social contact and food.

During the day, they reported their stress, mood and fatigue, while physiological stress responses, such as heart rate and cortisol were recorded.

These bouts of social isolation “led to lowered, self-reported energetic arousal and heightened fatigue, comparable with food deprivation”.

To test whether these findings would extend to a real-life setting, the researchers conducted “a preregistered field study during a COVID-19 lockdown”. This involved 87 adults, 47 of them women.

From this study, they used data from participants who had spent at least an eight-hour period in isolation and whose stress and behavioural responses were assessed with the same measurements several times a day for seven days.

And the results?

The drop in “energetic arousal after social isolation” seen in the lab was replicated in the field study “for participants who lived alone or reported high sociability”.

This suggested that lowered energy could be part of a homeostatic response to a lack of social contact.

“In the lab study, we found striking similarities between social isolation and food deprivation. Both states induced lowered energy and heightened fatigue, which is surprising given that food deprivation literally makes us lose energy, while social isolation would not,” the authors wrote.

It may be that lowered energy may be a part of our homeostatic response to a lack of social contact “and a potential precursor of some more detrimental effects of long-term social isolation”.

In other words, a warning that being without social contact for too long  could cause other serious health problems.