Can loneliness harm my health?

Trainee doctor Isabelle Cochrane weighs up the evidence around the impact of loneliness on health...

Isabelle - It is reasonably intuitive that social isolation might be bad for one's health, as this state could potentially limit access to health care resources. However it is less clear how experiencing the emotion of loneliness might be harmful. In order to try to measure loneliness distinctly from social isolation many studies use standardize questionnaires such as that UCLA loneliness scale. In this way it has been found that the subjective state of loneliness in itself has a much bigger impact on a person's health than any other element of their social network, including number and frequency of social contacts and the presence of close relationships.

In other words it is reasonable to believe that any negative health outcomes are genuinely stemming from loneliness rather than social isolation. Another difficulty is that loneliness, rather than being static, is a state that fluctuates with time and as one's social circumstances change. Any of us can feel lonely at any time and some people feel lonely most or all of the time.

Additionally there is a well-documented loneliness trajectory across a lifetime, with the highest rates of loneliness occurring in late adolescence, a trough in middle age and an increase once again in old age. There are intergenerational differences in the rates of loneliness, with millennials recently found to be the loneliest generation, much more so than generation X or baby boomers. Many studies of loneliness look at a particular point in time or a short interval, rather than entire lifetime, and therefore it can be hard to draw conclusions about the impact of chronic loneliness versus temporary loneliness, loneliness and young age versus loneliness in old age, and whether resolving loneliness can reverse the associated negative health impacts.

Despite these caveats, there is reasonably strong evidence that loneliness leads to increased mortality, particularly in older adults. Strikingly the effect of loneliness on mortality appears to be as great as that of smoking. It is not entirely clear what the mechanism of this effect is. Loneliness has been linked to a worsening of cardiovascular risk factors such as blood pressure and cholesterol, which may go some way to explaining this increased mortality.

Indeed, the longer the period of loneliness lasts, the worse these measures of cardiovascular health become. Other research suggests that those who are lonely tend to lead less healthy lifestyles, drinking and smoking more, taking less exercise and seeking medical attention less factors which also worsen cardiovascular health. This might lead us to think that those who are lonely have worse cardiovascular health because they lead less healthy lifestyles overall. But this does not appear to be the case. When studies control for these lifestyle factors, loneliness still emerges as an independent risk factor for mortality. This is now leading onto research into the potential effects of loneliness on a cellular and a molecular level. Lonely individuals show differences from hormone production all the way down to gene expression, in particular in ways that increase the levels of inflammation in the body and worsen the function of the immune system.

Loneliness also impacts negatively on one's psychological well-being, with people with chronic and high levels of loneliness showing increases in all manner of psychiatric conditions including depression, suicide and psychosis. One might consider this a chicken and egg scenario. Is the loneliness causing a psychiatric pathology or is worse social functioning due to a psychiatric condition causing the loneliness?

However there is evidence that measuring loneliness in an individual can predict the onset of depressive symptoms, whereas measuring the extent of depression an individual does not predict the onset of loneliness, suggesting that it is the loneliness that comes first.

In a similar vein, loneliness has also been associated with cognitive decline and Alzheimer's disease. It is tempting to think  that this effect is due to social isolation with the explanation that fewer social interactions lead to less simulation of the brain and hence less good cognitive function. But once again, it emerges that poor quality and satisfaction with social interactions is much more predictive of the onset of dementia than a low number of social interactions per say. However more research is required to show conclusively whether the loneliness precedes the cognitive decline or vice versa.

All of the above makes a compelling case for us to try to reduce the levels of loneliness experienced by people at any age. However there is no known intervention that can be administered by health care professionals that has been shown to be effective in abolishing loneliness and reversing its effects on a person's health.

So if you do have a friend or neighbour or colleague who you think might be lonely, today is as good a day as any to invite them over for a cup of tea.