The bachelor status could make you proud, but will make your life shorter. A team of psychologists at University of Chicago tracked down social loneliness and its physical effects, connected with aging, right down to the cell level. The scientists found that even if loneliness could be mild and unnoticeable in early life, its effects are accumulative.

The team investigated a group of college students and one of people that were 50 to 68 years old.

Stress was the factor they focused on. The more you live, the more stressful experiences you accumulate: new jobs, marriage and divorce, parenting, financial worries, diseases.

But the researchers found that even when the lonely individuals reported the same number of stressful events in their life like the 'not lonely' ones, they presented more sources of chronic stress and recalled more childhood negative events. They also perceived life experiences differently: when faced with similar challenges, the lonely people felt more helpless, threatened and unable to actively look for help.

Urine analysis revealed higher levels of epinephrine, a stress hormone, in the bodies of the lonely individuals. This means that lonely people experience a perpetual state of arousal. In the case of blood pressure, this physiological effects were more likely to manifest with aging.

As stress hormones decrease the immune capacity, inflammation and infection in loneliness could act more aggressively in the wear and tear effect of aging.

Moreover, loneliness linked to stress affected severely the sleep quality. The lonely individuals had a sleep impaired by many "micro awakenings", so that even when they sleep as much as the non-single subjects, the lonely ones reported more daytime dysfunction. Sleep loses quality with age anyway, thus the effects of loneliness will be even severer with age.

The researchers warn that loneliness is different from solitude. Some people can find comfort in being alone, but for many, social isolation induces an intense stress.