This is one of the extreme forms of stress that a human being can be subjected to. Evolution has favoured us with a large number of tools like language, emotions, and a hugely developed brain; that makes social cohesion possible and even necessary. It is obvious that depriving a person of this basic human requirement is a cruel punishment.
No wonder, even the most hardened criminals dread the prospect of ‘solitary confinement’. Social interactions can have a positive effect and would be one of the strategies employed for stress reduction. It should come as no surprise that other primates exhibit the same need for social interaction.
A large number of studies have demonstrated that social isolation for long periods leads to immune suppression and diseases associated with such suppression. Many of those studies were prospective—that is they were tracking people before the social isolation and then studied the results afterwards. These studies are extremely time consuming and costly. The short cut is to find people suffering from the disease and then ask them about the stressful things in their lives (retrospective studies).
The obvious drawback is that human memory is very unreliable when it comes to suffering. When sick, we tend to exaggerate the conditions that we think may have caused the disease. So it helps to have prospective studies where such bias of human memory has been removed. Such studies have confirmed a strong link between stress and immune suppression.
The fewer social relationships a person has, the shorter the life expectancy and higher the impact of various infectious diseases. In medical terms, a relationship can take any form—marriage, friendship, religious affiliation and belonging to organized groups. In particular, separation from a spouse or facing severe marital difficulties is associated with worse immune functioning. Other studies have found that people who are very lonely (measured in scientific terms on a loneliness scale) have been found to have relatively higher depressed immune systems and higher risk of death.
Therefore, we find a lot of scientific literature on the subject that affirms the idea that social isolation leads to higher immune suppression. The obvious question to ask is how big is this impact on the chances of getting disease? The answer is that it is a very big factor. It is as big a risk factor as cigarette smoking, obesity, hypertension and low level of physical activity. In one study, it was found that people with the fewest social connections had almost two and a half times as much chance of dying as those with most connections.6
People who are socially isolated are more stressed and have fewer outlets fot their frustration and lack support. This leads to chronic stress and activation of the stress response, which leads to immune suppression and finally more infectious diseases. Obviously, there are a few other explanations for this phenomenon too. For example, lonely people may not have loved ones asking them to be careful and to look after their health. Simple things like eating out more instead of their home may lead to poor health and higher incidence of disease.
Turning the question around—is it the case that sickly people tend to be socially isolated? These are valid counterpoints and help to explain other ways in which social isolation may bring about immune suppression. Careful studies show that stress is one of the major factors in suppressing the immune system in socially isolated people.
One of the extreme forms of social isolation is bereavement and a number of studies have shown that the death of a spouse leads to poorer health in the survivor and that there is a higher incidence of death. Popular fiction and movies have used this theme of the grieving spouse pining away for the dead partner and eventually dying.