Work and relationship pressures make the mid-30s the start of many British people's unhappiest decade, a survey suggests.
Of the 2,000 people quizzed, more aged 35 to 44 said that they felt lonely or depressed than in other age groups.
The survey also suggested that busy parents were using Facebook and similar sites to stay in touch with children.
Relationship advice charity Relate, which is behind the research, said it revealed a "true mid-life crisis".
Of those surveyed, 21% of men and women aged 35 to 44 said they felt lonely a lot of the time, and a similar percentage said that bad relationships, either at work or home, had left them feeling depressed.
The same proportion said they felt closer to friends than family, and a quarter said they wished they had more time for their family.
Claire Tyler, Relate's chief executive, said: "Traditionally we associated the mid-life crisis with people in their late 40s to 50s, but the report reveals that this period could be reaching people earlier than we would expect.
"It's no coincidence that we see people in this age group in the biggest numbers at Relate."
Professor Cary Cooper, the president of the charity and a researcher in work stress at Lancaster University, said that things were only likely to worsen in the current economic climate, as more was demanded of fewer employees.
He said: "We're already working the longest hours in Europe - if you constantly work people long hours it's not good for their health.
"The annual cost of work-related mental health problems is estimated at £28bn, so it's clearly a massive problem."
The survey, conducted in collaboration with phone and broadband firm Talk Talk, revealed that 28% of 35 to 44-year-olds questioned said they had left a job because of a bad working relationship with a colleague.
It also shed light on how family relationships are standing up to modern life.
While most people described their relationship with their partner as in positive terms, one in five was worried about the current financial climate.
Working long hours, arguments, proper division of household chores and poor sex were cited equally by men and women as the most common sources of problems.
Dr Jane McCartney, a chartered psychologist with an interest in adult mental health, said that it was possible that the results for 35 to 44-year-olds might be slightly skewed by the willingness of people in that age group to be frank about depression and loneliness, compared to older people surveyed.
She added: "However, there might certainly be a grain of truth in what they've found - there are higher expectations on people of this age in terms of what they've achieved in their careers and family life."
BBC News website readers have sent in their comments:
I had mine at 29. At least that's when I quit my job, changed direction and ended up doing something radically different. I'm now 37 and have never been more settled or happier. Kate, Oxford
I agree with the article. I had been married for 14 years before my divorce aged 38. Work pressure meant I had no time for my family or friends who, in turn, had no time for me either. When you do get some free time you're too broke to make the most of it and your life can become a long hard slog with little joy to make the hard times seem worthwhile. Now I am working just as hard and have far more money worries but do make time for my son and my friend. It is far too easy to sit at home feeling lonely and sad and can soon become a habit. It takes effort and willpower to break free of that and bring some sunshine into your life. Andy, Nottingham
I am 41, but I remember a few weeks before my 35th birthday having an almighty panic attack because suddenly I was staring my forties in the face, and was no longer part of the 20s-30s generation. It was pure fear of my life slipping away. And bad news, guys, once that fear is there, it never leaves you! The Pink Floyd album Dark Side of the Moon is all about this subject. Matthew Brain, Streatham, London
I reckon that in 90% of cases just one thing is to blame for such a crisis: failure to find a route in life. Whether this failure is settling into a permanent relationship, or finding the career that is both satisfying and rewarding, is up to the individual. Even not being able to move into bricks and mortar that are your own and not a poverty-related rented flat can prove stressful. Women obviously have the added stress of the body-clock factor; even those women I know who don't really feel the urge to procreate are aware and stressed that their choices in this issue are being constrained merely by their age. Men, I feel, are suffering from a loss of knowing what their role is in life now that women can fend for themselves, and this is hugely stressful on both their psyche and their health. This stress factor can also grate upon the well-being of women. All of which makes a perfect time bomb for a mid-life crisis as women and men approach their frightening forties. Madeleine, Durham
I'm now 41 but couldn't agree more with the findings in this article. So much pressure is brought on us over career achievements, status symbols like cars and also family pressures. I pretty much failed on all levels when I hit 36 onwards as everything seemed to evaporate in front of my eyes. They are a nothing decade as you are not far enough away from your 20s to stop trying to keep up with the younger crowd and are too young to want to mix with those in their 40s. Now at 41 years of age I feel a lot more settled both professionally and personally and also, ironically a lot more at ease in socialising with people of all ages. Darren Pearce, Manchester
I suspect this has a lot to do with the fact that it's probably the most typical age range people get divorced (for the first time), and mid-40s is now more likely to be the age when people experience work-place ageism for the first time. James Stevens, Windsor
I most definitely had a quarter life crisis a while ago, at 25. I was struggling to get ahead in my chosen career, fed up of not having a firm relationship and not being able to afford to move out of the family home, after having a taste of freedom at uni. I realise my expectations of being settled or on my way to being settled in life by 25 may have been a bit high but I definitely remember feeling very inadequate and despondent. Maybe our own expectations of life cause us to have these kinds of crises every decade? Emily Liscott, Guildford
I've just finished reading The Middle Passage by Dr James Hollis. Rather than viewing it as a mid-life crisis it can be seen as an opportunity to re-evaluate our lives both as the world around us changes but also as we develop and grow within ourselves. Just as a rocket to the stars sheds the spent stages of its fuel so we need to shed the values and beliefs that perhaps supported us through one stage of our life but are no longer relevant for the next stage. Being out of sync with ourselves and our surroundings can cause depression, fear and loneliness. The challenging process of reconnecting with ourselves and the world around us can re-ignite the flames that power us forward in our journey to a better life. Duncan Munro, Aberdeen
I found that I stay happier if I record my mood over the year. It keeps everything in perspective and helps me remember the happier times, and that happy times will return. Sam Johnson, London
I've just turned 45 recently, and I feel like I'm on a hamster wheel. Society gets me down and I'm starting to get aches and pains. It's all happened in the last five years. But hey-ho, life goes on. Robert Leahy, Coventry
As a 30-something generation X-er we've had our hopes and expectations falsely raised our whole lives. We were told as children that if you work hard you can achieve anything you set your mind to. Well, for the vast majority, you can't. You have to take the middle-of-the-road jobs that are available. I think our parents are happier as they had no career expectations and hence weren't disappointed by 40 years in middle-management and an average pension. Barry Smith, Bristol
I am a 36-year-old recently divorced mother of one. My son is five years old and I find that I feel very lonely in the evenings, and money is also tight. I cannot see things changing and therefore feel down. I definitely feel like I am having a mid-life crisis! Katy, Guernsey
As an American, with less social care, even longer work hours and even less holiday I can certainly relate. We are the first generation to do worse than our parents. Retirement and home ownership seem unobtainable even in a double income household with no children. Add the crushing yet necessary masters degree and school debt just to remain competitive and you have a long drawn-out hum of futility. It can be a bit of a challenge to keep your chin up at times. Ann, San Diego, California, US