'Feeling isolated can disrupt sleep, raise blood pressure, weaken immunity, increase depression and lower subjective wellbeing.' Photograph: Ocean/Corbis
That loneliness is a health issue would not have been a surprise to Mother Teresa who once said: "The biggest disease today is not leprosy or cancer or tuberculosis, but rather the feeling of being unwanted, uncared for and deserted by everybody."
But now doctors have quantified the effects of the loneliness disease, warning that lonely people are nearly twice as likely to die prematurely as those who do not suffer feelings of isolation. Being lonely it seems, is a lot more worrying for your health than obesity.
In a report called Rewarding Social Connections Promote Successful Ageing that Professor John Cacioppo presented in Chicago at the weekend, the effect of satisfying relationships on the elderly was measured.
Cacioppo's team found that friendships helped older people develop their resilience and ability to bounce back after adversity, as well as an ability to gain strength from stress rather than be diminished by it.
Not surprisingly, there is no corresponding good news for those less well connected to other people. Loneliness has dramatic consequences on health. Feeling isolated from others can disrupt sleep, raise blood pressure, lower immunity, increase depression, lower overall subjective wellbeing and increase the stress hormone cortisol (at sustained high levels, cortisol gradually wears your body down).
Older people can avoid the consequences of loneliness by staying in touch with former colleagues, taking part in family gatherings and sharing good times with family and friends, says Cacioppo. Moving away from an established community to retire to a seaside idyll could often be a mistake, but such good common sense probably doesn't go far enough.
The Lonely Society, a 2010 report commissioned by The Mental Health Foundation, cited a link between our "individualistic society" and the increase in common mental health disorders in the last 50 years.
It also drew on research showing that mental health problems occur more frequently in unequal societies where vulnerable people are often left behind. By squandering "social capital" in the individualistic pursuit of greater wealth, or treating social networks as incidental, are we neglecting a part of life that makes us happy and keeps us healthy for longer?
This report also quotes research that suggests lonely people often share certain characteristics: these include more of a history of loss or trauma and a childhood spent with negative, critical and harsh parenting.
Loneliness is often the core feeling that gives rise to emotions of anger, sadness, depression, worthlessness, resentment, emptiness, vulnerability and pessimism. Lonely people frequently feel that they are disliked, are often self-obsessed and lack empathy with others. They fear rejection and keep themselves at a distance, which feeds the loneliness.
People who are lonely often think that everyone else is doing OK while they are not. They think they are the only ones carrying a burden. I have had clients talk about putting their "game face" on rather than sharing truthfully about themselves. And it can be difficult to know when it is appropriate to make the move from the former to the latter.
So in an ageing society with more and more people living on their own, what is the solution? I believe that it is never too late to change, and that psychotherapy can help people to heal the wounds from their past and establish new patterns of relating to others. But a dependency on this specialist relationship may also develop, with the therapist becoming a substitute for developing confidants outside the consulting room.
I am on the advisory board of The Talk for Health Company Ltd (T4H) which is a social enterprise set up by psychotherapist Nicky Forsythe. It trains people in the loneliness-stopping skills of authentic sharing and empathic listening. After a short initial training, the groups set up long-term peer support systems that are proven to improve wellbeing significantly. The ultimate aim of T4H is to create networks of confidants where anyone can find a place to connect at a deeper level.
It seems that at least some GPs and health managers do realise that combating loneliness is key to maintaining good health. A forward-looking scheme funded by the NHS in Islington will this year fund 12 Talk for Health programmes, offering 180 free places to Islington residents for adults at any stage in life.
People without access to such a programme could also consider joining a 12-step group such as Emotions Anonymous or Depression Anonymous, where they will be able to put aside their "game faces" and share truthfully about themselves on a deeper level. Unlike individual psychotherapy, the connections made in such groups can be integrated into the participants' lives beyond the group.
Such schemes can help people of any age to develop self-acceptance, making it easier for them to relate to others and connect on such a level that loneliness, if not eradicated, at least becomes less of a threat to health.