Social isolation

Social isolation is a state of complete or near-complete lack of contact between an individual and society. It differs from loneliness, which reflects temporary and involuntary lack of contact with other humans in the world. Social isolation can be an issue for individuals of any age, though symptoms may differ by age group.

Social isolation has similar characteristics in both temporary instances and for those with a historical lifelong isolation cycle. All types of social isolation can include staying home for lengthy periods of time, having no communication with family, acquaintances or friends, and/or willfully avoiding any contact with other humans when those opportunities do arise.

True social isolation over years and decades can be a chronic condition affecting all aspects of a person's existence. Social isolation can lead to feelings of loneliness, fear of others, or negative self-esteem. Lack of consistent human contact can also cause conflict with (peripheral) friends. The socially isolated person may occasionally talk to or cause problems with family members.

The magnitude of risk associated with social isolation is comparable with that of cigarette smoking and other major biomedical and psychosocial risk factors. However, our understanding of how and why social isolation is risky for health – or conversely – how and why social ties and relationships are protective of health, still remains quite limited.

In the case of mood-related isolation, the individual may isolate during a depressive episode only to 'surface' when their mood improves. The individual may attempt to justify their reclusive or isolating behavior as enjoyable or comfortable. There can be an inner realization on the part of the individual that there is something wrong with their isolating responses which can lead to heightened anxiety. Relationships can be a struggle, as the individual may reconnect with others during a healthier mood only to return to an isolated state during a subsequent low or depressed mood.

Research indicates that perceived social isolation (PSI) is a risk factor for and may contribute to "poorer overall cognitive performance and poorer executive functioning, faster cognitive decline, more negative and depressive cognition, heightened sensitivity to social threats, and a self-protective confirmatory bias in social cognition." PSI also contributes to accelerating the ageing process: Wilson et al. (2007) reported that, after controlling for social network size and frequency of social activity, perceived social isolation is predictive of cognitive decline and risk for Alzheimer's disease. Moreover, the social interactions of individuals who feel socially isolated are more negative and less subjectively satisfying. This contributes to a vicious cycle in which the person becomes more and more isolated.

In the first resting state fMRI functional connectivity (FC) study on PSI, PSI was found to be associated with increased resting-state FC between several nodes of the cingulo-opercular network, a neural network associated with tonic alertness. PSI was also associated with reduced resting-state FC between the cingulo-opercular network and the right superior frontal gyrus, suggesting diminished executive control. Cacioppo and colleagues (2009) found that lonely individuals express weaker activation of the ventral striatum in response to pleasant pictures of people than of objects, suggesting decreased reward to social stimuli. Lonely individuals also expressed greater activation of the visual cortex in response to unpleasant depictions of people (i.e., negative facial expressions) than of objects; non-lonely individuals showed greater activation of the right and left temporoparietal junction (TPJ), a region implicated in theory of mind. The authors interpreted the findings to represent that lonely individuals pay greater attention to negative social stimuli, but non-lonely individuals, to a greater degree than lonely individuals, insert themselves into the perspective of others. Moreover, Kanai et al. (2012) reported that loneliness negatively correlated with gray matter density in the left posterior temporal sulcus, an area involved in biological motion perception, mentalizing, and social perception.

Overall, several neuroimaging studies in humans on perceived social isolation have emphasized implications of the visual cortex and right-hemispheric stress-related circuits underlying difference between lonely and non-lonely individuals. A 2020 population-genetics study marked a 50× increase in the neuroimaging research on perceived social isolation. The investigators tested for signatures of loneliness in grey matter morphology, intrinsic functional coupling, and fiber tract microstructure. The loneliness-linked neurobiological profiles converged on a collection of brain regions known as the default mode network. This higher associative network shows more consistent loneliness associations in grey matter volume than other cortical brain networks. Lonely individuals display stronger functional communication in the default network, and greater microstructural integrity of its fornix pathway. The findings fit with the possibility that the up-regulation of these neural circuits supports mentalizing, reminiscence and imagination to fill the social void.