Having a very close relationship with another person may be the best medicine for people who have had a heart attack, research suggests.
Scientists have shown that a strong bond - whether it be with a friend, lover or relative - can halve the risk of further heart attacks.
The researchers, from Manchester Royal Infirmary, believe having somebody to talk to helps people cope better.
The research, based on a study of 600 patients, appears in the journal Heart.
The volunteers who took part in the study were screened three to four days after having had a heart attack.
They were also monitored for a further 12 months to assess their risk of further attacks or death.
About one in four of those screened had been depressed before having their first heart attack - suggesting state of mind may influence risk.
However, despite findings from previous research, these patients were no more likely to have a further heart attack or to die than the patients who were not depressed.
But the researchers found that patients who had a close friend or relative in whom they could confide had half the risk of those without such a confidant.
This was the case even after taking account of the severity of the heart attack and other risk factors.
Patients without a very close relationship were more likely to drink heavily, to use illegal drugs, and to have had at least one previous heart attack before admission.
The finding echoes a previous study by the University of Chicago which found that lonely people's cardiovascular systems worked differently to those of people who were not lonely, in ways which put them at higher risk of heart disease.
Lead researcher Professor Francis Creed told BBC News Online that a variety of factors seemed to increase the risk of recurrent heart attacks.
These included smoking, heavy drinking, little exercise, and poor diet - but also depression and lack of social support.
He said that stress and depression tended to make the heart beat faster, and keep the body in a more aroused state.
He said: "We think that people who have no close confidant may react to stress in a more pronounced fashion.
"This is potentially dangerous, as in the post-heart attack phase the heart is more susceptible to arrthymias [disrupted rhythms]."
The researchers also found that people without a very close relationship were twice as likely to have lost both parents during childhood as patients who enjoyed a very close relationship with another person.
They speculate that separation from parents during childhood might adversely affect the chances of forming an intimate relationship as an adult.
Belinda Linden, of the British Heart Foundation (BHF) which co-funded the research, said: "This research is helping us to understand how important such psychosocial factors can be in preventing further cardiac events.
"A close relationship - whether it be a lover, friend or relative - is obviously a potentially vital source of social support, which can play an important role in both preventing coronary heart disease and enhancing recovery from a heart attack."