Loneliness is an important social determinant of health. Systemic reviews have shown that the influence of social relationships on the risk of death are comparable with well-established risk factors for mortality such as smoking and alcohol consumption, and exceed the influence of other risk factors such as physical inactivity and obesity. People with stronger social relationships had a 50% increased likelihood of survival than those with weaker social relationships.
Loneliness is the unpleasant feeling we can experience when there is a mismatch between the social relationships we have and those we would like to have. It includes emotional and social aspects.