A life of booze, fags and slothfulness may be enough to earn your doctor's disapproval, but there is one last hope: a repeat prescription of mates and good conversation.

A circle of close friends and strong family ties can boost a person's health more than exercise, losing weight or quitting cigarettes and alcohol, psychologists say.

Sociable people seem to reap extra rewards from their relationships by feeling less stressed, taking better care of themselves and having less risky lifestyles than those who are more isolated, they claim.

A review of studies into the impact of relationships on health found that people had a 50% better survival rate if they belonged to a wider social group, be it friends, neighbours, relatives or a mix of these.

The striking impact of social connections on wellbeing has led researchers to call on GPs and health officials to take loneliness as seriously as other health risks, such as alcoholism and smoking.

"We take relationships for granted as humans," said Julianne Holt-Lunstad, a psychologist at Brigham Young University in Utah. "That constant interaction is not only beneficial psychologically but directly to our physical health."

Holt-Lunstad's team reviewed 148 studies that tracked the social interactions and health of 308,849 people over an average of 7.5 years. From these they worked out how death rates varied depending on how sociable a person was.

Being lonely and isolated was as bad for a person's health as smoking 15 cigarettes a day or being an alcoholic. It was as harmful as not exercising and twice as bad for the health as being obese. The study is reported in the journal Plos Medicine.

Holt-Lunstad said friends and family can improve health in numerous ways, from help in tough times to finding meaning in life. "When someone is connected to a group and feels responsibility to other people, that sense of purpose and meaning translates to taking better care of themselves and taking fewer risks."

Holt-Lunstad said there was no clear figure on how many relationships are enough to boost a person's health, but people fared better when they rarely felt lonely and were close to a group of friends, had good family contact and had someone they could rely on and confide in.

Writing in the journal, the authors point out that doctors, health educators and the media take the dangers of smoking, diet and exercise seriously, and urge them to add social relationships to the list.

A report by the Mental Health Foundation in May blamed technology and the pressures of modern life for widespread feelings of loneliness in all age groups across Britain. The survey of more than 2,200 adults found one in 10 people often felt lonely and one in three would like to move closer to their family.

Andrew McCulloch, of the Mental Health Foundation, said the latest study builds on work that links isolation to poor mental and physical health. "Trends such as increasing numbers of people living alone and the advent of new technologies, are changing the way in which we interact and are leading both the young and old to experience loneliness. It is important that individuals and policy-makers take notice of emerging evidence and of the potential health problems associated with loneliness."