Loneliness: A Matter of Genetics?

Loneliness is part of the human condition—the experience is universal. After all, we are the only humans in our heads.

According to an article in the Economist, loneliness also increases mortality. Apparently, studies that followed 300,000 people, found that loneliness is just as unhealthy as smoking and drinking. UCLA professor of psychoneuroimmunology Steven Cole hypothesized that this may be because being lonely changes the way our immune cells read their DNA–which genes are expressed.

Dr. Cole analyzed gene expression in 14 people, six people in this group were categorized as severely lonely and one was not lonely at all. He found that lonely people tend to express genes that mediate a nonspecific immune response and less lonely people express genes that mediate an immune response tailored to making antibodies (which recognize and mark foreign invaders in our bodies) and fighting viruses. The conclusion the researchers drew was that being lonely increases one’s risk of inflammation-mediated disease by altering gene expression in immune cells–it triggers an unhealthy immune response. They then went on to speculate on how this could have occurred evolutionarily.

Were their conclusions, as reported in the Economist, warranted? Well, they are premature at best and huge leap at worst. Let’s follow the logic. The gene expression in a specific fraction of the cells in a very small number of lonely people appears different from that in a different fraction of cells in one person who does not appear to be lonely. Therefore, “past evolution has created a mechanism (the details of which remain unclear) which causes white cells to respond appropriately,” but since evolution has not caught up to our modern way of life, natural selection has not yet “dealt with” chronically lonely people (who are immunologically less fit).

One step at a time. Note that Dr. Cole only analyzed immune cell gene expression. But, there are lots of other cells types in the human body and most of them are involved in some disease or other. In addition, the study was only performed in 14 people; the numbers in each “loneliness” category were even smaller. Quite apart assessing the accuracy of this psychological assessment, one also needs to consider if correlation necessarily implies causation. After all, Dr. Cole only notes a difference in gene expression, not a difference in immune system function–and then makes the leap to connect this to a psychological state. Finally, to suggest that this is somehow connected to the overarching evolution story may make it more likely to be published, but certainly does not add scientific information.

There is a difference between reporting of data, accurate and balanced interpretation of the data, and speculation. It is not that speculation should never occur, but that the public needs to understand when it does.