The great American author John Steinbeck once said: "A sad soul can kill you quicker, far quicker, than a germ."
Steinbeck's words received a 21st Century echo this week by Dr Helen Stokes-Lampard, Chair of the Royal College of General Practitioners, who urged GPs to make time to see more lonely patients. She warned social isolation and loneliness are "akin to a chronic long-term condition in terms of the impact they have on our patients' health and wellbeing."
At its most extreme, loneliness can increase the risk of premature death by 50%. That's about the same as living with chronic obesity.
We also know lonely people are more likely to sleep badly, feel tired and have trouble concentrating during the day. This increases their risk of developing mental health problems such as anxiety, stress, depression and eating disorders.
Part of the challenge for all of us is ensuring we truly understand what loneliness is. Loneliness isn't just about being physically alone; equally damaging can be the feeling of being alone.
Someone who knew this better than most was Jo Cox. She knew loneliness affect us all. In her own words: "young or old, loneliness doesn't discriminate." So I was honoured to speak at a meeting organised in her name as part of the Jo Cox Loneliness Commission this week.
We often hear stories of elderly people who have little or no contact with other human beings. Shockingly, the television is currently the main form of company for over 3 and a half million people aged 65 and over.
That's why it's crucial we support the work of organisations such as the Campaign to End Loneliness, who are working incredibly hard to try and reach the estimated 1 million elderly people who are affected by loneliness in our communities.
Children and young people in schools and colleges are also especially vulnerable. More than 4,000 children have contacted Childline in the past year because they were lonely.
I think social media has heightened this trend, and it's clear that we need a strategy to tackle this.
Even Justin Rosenstein, the Facebook engineer who created that like button we all use on a regular basis, has weaned himself off his own product blaming the worrying rise of the so-called "attention economy". And with the average person touching, swiping or taping their phone 2,617 times a day, he's got a point.
It seems that the technology which has brought us closer together in ways unimaginable just a decade ago, has actually left many of us feeling more alone than ever, even in our tightest circles.
We also know from the challenges in tackling mental health problems more widely that stigma remains a central barrier in tackling loneliness. 1 in 3 people feel embarrassed to admit they are lonely and, again, this is frequently the case among young people.
It's why I firmly believe we need a national strategy to tackle loneliness, something which this Tory Government has failed to implement.
A national strategy is needed to help local authorities and the health service to promote awareness of loneliness. It must ensure every community has the appropriate blend of services, fully funded to meet the wide range of individual need.
Labour's strategy will include the full participation of lonely people, businesses, faith groups and statutory departments. We will encourage cross-departmental co-operation to ensure a more coordinated and measured approach towards tackling loneliness and promoting wellbeing.
The urgency of this important issue was crystal clear yesterday during an informative roundtable event I attended with Luciana Berger MP, the conclusions of which will feed ideas into the Jo Cox Loneliness Commission.
I heard the desperate story of how one elderly lady didn't see, and therefore speak, to another human being for so long that she lost her voice.
Sadly, I suspect similar stories are being heard right across the country.
That's why if we are to solve the scourge of loneliness, something Jo was absolutely certain we could achieve, we must ensure local authorities receive the funding they so desperately need. Local initiatives ranging from patient transport systems to social clubs all require adequate funding, and all play a major role in tackling loneliness.
However, this Government is cutting £800 million from public health budgets between 2015/16 and 2020/21. My own research has found that funding for social isolation services has fallen over the past 2 years, meaning too many local authorities are unable to sufficiently fund important social support services.
So one of the most important things Labour will do, will be to protect public health budgets from further Tory cuts.
For too long loneliness has been neglected as a significant health issue. We cannot ignore the crisis any longer.