Loneliness may predict functional decline and death.
Those living by themelves or just feeling lonely have a 25% increased risk for all-cause mortality and cardiovascular death--especially in younger subjects (under 80). In another study, feelings of loneliness in those over 60 years of age were approximately 60% more likely to experience declines in their ability to carry out daily tasks.
PositiveTip: Provide some social support to someone you know who is lonely. It may help them and you!