Loneliness and social isolation may be as big or an even bigger threat to health than obesity and inactivity. Loneliness, social isolation and living alone raised a person's risk of dying in the next seven years by almost a third, according to an analysis of 70 different studies.

The effect was stronger on middle-aged people than on the elderly.

Research into the effect of loneliness on health is in its infancy. The Brigham Young University researchers say it's similar to the situation that existed regarding suspicions about the negative health effects of overeating and sedentary lifestyles three decades ago.

While most studies of loneliness have focused on the elderly, the effect was stronger in younger people.

Today, nearly everyone has heard of the obesity crisis, but in the 1980s alarms were just beginning to be raised about the effects of junk food and a lack of physical activity on health. Now, the study authors warn of a potential loneliness crisis.

“Not only are we at the highest recorded rate of living alone across the entire century, but we're at the highest recorded rates ever on the planet,” Tim Smith, co-author of the study, said in a statement. “With loneliness on the rise, we are predicting a possible loneliness epidemic in the future.”

The authors reviewed 70 studies published during the last 35 years that measured the effect of loneliness and/or social isolation and living alone on people's mortality. Overall, the studies included nearly 3.5 million people, average age 66, who were typically followed-up at 7 years.

Even after making adjustments for factors such as socioeconomic status, age and pre-existing health conditions (sicker people are likelier to die sooner), there was a substantial increase in mortality seen in those who were lonely, socially isolated or lived alone.

While most studies of loneliness have focused on the elderly, the effect was stronger in younger people. For people under 65, the mortality increase was 57%. For those between 65 and 75, it was 25%.

But the news isn't all doom and gloom. While loneliness and isolation have serious health consequences, the results also mean that relationships and social connections can be good for your health. As Smith puts it, “In essence, the study is saying the more positive psychology we have in our world, the better we're able to function not just emotionally but physically.”

The study appears in Perspectives on Psychological Science and is freely available.