Many things happen when one is lonely. Lonely people, not only drink more, they also eat more. Food presumably tries to fill the space created by loneliness. Lonely people find greater fault with themselves, and also those around them. Some people are socially isolated and they are not lonely. Some people are lonely even if they have a lot of social contacts. The anxiety that accompanies loneliness is a warning that an individual’s social ties have gotten too weak. Loneliness increases wear and tear by keeping the body in alert mode. It may also prevent people from recharging their batteries with rest and relaxation. Loneliness is good if it is short term. Loneliness is bad if it is too prolonged. Researcher on loneliness, John Cacioppo says, loneliness is a survival impulse, like hunger or thirst. Food is needed when one is hungry. Similarly lonely people need the nourishment of human companionship.

Cacioppo says, loneliness at the individual scale is hostile, but at the species scale it is beneficial. In loneliness, Cacioppo sees interdependence of social and biological processes. In the presence of the other, the possibility of survival seems better. Cacioppo believes loneliness is moderately heritable and the symptoms of loneliness outlast loneliness. It is also true that the benefits of feeling connected persist even after the connections wither. Cacioppo found that people scoring high on the loneliness scale tend to exhibit several physiological changes that effectively put the body in a state of alert. Social disconnection may impair the ability to control thoughts, emotions, and impulses. Loneliness makes sleep less restful. Cacioppo says the brain still hears that ancient warning that people are most vulnerable when they are asleep. Researchers say that the stress of social isolation disrupts a brain region responsible for emotional and cognitive behaviour. The socially isolated tend to imbibe the spirit of social avoidance and withdrawal. The researchers, however, observed that once social integration was re-established, the possibility of reversal of negative consequences of social isolation was possible.