Biology Magazine

Social Isolation: as Unhealthy as Smoking

Posted on the 29 September 2016 by Reprieve @EvoAnth

Humans and chimps split around 7 million years ago. Since then our lineage has accumulated many unique traits. Like losing all our hair and walking upright. Arguably the most important of these is our intense sociality. We banded together into large, complex groups that put the rest of the primate world to shame. Now, we're effectively reliant on these groups for survival. Social isolation - even if you're still living in society - can be a major health hazard. By some measures, it's almost as bad as smoking.

Of course, there was a reason our species became so social in the first place. Being more connected is associated with a whole host of benefits. Even some weird ones. For example, dancing together in a group (and bonding as a result) makes you more resistant to pain. Which is good. If you had to see me dance you definitely need more pain resistance.

Isolation is bad

Imagine you made a list of all your friends. Then, they had to do the same. If you were all as good friends as you thought, you should all be cropping up on each others' lists. However, if nobody really liked you a discordance would arise. And this is the crux of one of the most depressing scientific measurements I've ever come across: indegree. Simply put, it refers to how many incoming friendship nominations someone has. When compared to outdegree (your list of friends) it has the potential to reveal some very disappointing results.

These results may also be harmful to your health. Many studies have found that self-reported social isolation is correlated with poor health. In particular, with higher levels of fibrinogen. This is a molecule involved in blood clotting, which is normally useful. However, at high levels, it's linked with inflammation and cardiovascular problems. It's part of the reason smoking is so bad, as that can raise fibrinogen levels by 10%.

But self-reported data can be notoriously unbiased. So some researchers set out to see if a more objective measure of social isolation (indegree) showed a similar link with increased fibrinogen. Or is simply feeling what causes the problem? More than 3,000 individuals were examined for this research.

And the results show that social isolation is actually what's bad for you. Their analysis found outdegree (or self-reporting friends) had much less of a link to fibrinogen levels than indegree. In fact, it raised fibrinogen more than twice as much as smoking.

Non-isolation is good

Over the course of human evolution, socialising has given us many benefits. It provides us with allies, mating opportunities, teachers and more. So over millions of years we've developed abilities that foster such behaviour. Our giant brains, for example, seem to have evolved to help facilitate our giant groups. Yup, it seems the fact we're smart enough to create devices with which you can read my words is (partly) a side-effect of socialising.

Of course, it's all well and good for evolution to give us these faculties for socialising. It has to encourage us to use them as well. Due to this, we've evolved so that socialising makes us feel good. We get a little squirt of endorphins when we bond, encouraging us to continue. This has been tested many times, but my favourite example is when researchers made people listen to Gangnam Style, Calvin Harris, and Wham!

Participants had to listen to these songs on headphones, creating a silent disco. Each also received a set of dancing instructions. When those instructions aligned, creating synchronous dancing, people bonded more. This socialising was linked to increased endorphins. The researchers used a pressure cuff to cut off blood flow to their arm. The amount of this pain they could tolerate - a proxy for endorphins - increased when people had bonded more over the dancing.


There's no magical reason for these results. Humans don't flourish by draining some ethereal social energy from one another. The simple fact of the matter is we've evolved to be very social animals. In the process, we've adapted to a system where we're helped by others (and give help in return). Missing out on this help puts increased pressure on us. This causes stress, strain, unhappiness, and high fibrinogen levels.

On the other hand, being social is great. We gain access to some of that sweet, sweet prosocial behaviour. This provides access to some obvious benefits. So evolution encourages us to do this. We've evolved to enjoy social circumstances. Hence the release of endorphins and pain tolerance that's associated with bonding.

We haven't risen above evolution. It continues to influence our behaviour every day. The fact you've probably got social media running somewhere else on this device is just one example of this.


Danesh, J., Collins, R., Appleby, P. and Peto, R., 1998. Association of fibrinogen, C-reactive protein, albumin, or leukocyte count with coronary heart disease: meta-analyses of prospective studies. Jama, 279(18), pp.1477-1482.

Kim, D.A., Benjamin, E.J., Fowler, J.H. and Christakis, N.A., 2016, August. Social connectedness is associated with fibrinogen level in a human social network. In Proc. R. Soc. B(Vol. 283, No. 1837, p. 20160958). The Royal Society.

Tarr, B., Launay, J. and Dunbar, R.I., 2016. Silent disco: dancing in synchrony leads to elevated pain thresholds and social closeness. Evolution and Human Behavior.

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