Anger is horrible for your heart. Depression shrinks your brains neocortex. The emotions are a neglected part of health and healthcare.

I’ve read this and similar studies and it seems to me that what can be truly destructive is social isolation, of which lonliness can be a result. We are deeply social creatures, and have been so since before we became modern humans. We use each other as reference points and reality checks, and without that sort of contact and feedback, our judgement suffers and perspective narrows. Our greatest achievements have been collaborative (science, for instance). Downside can be groupthink, peer pressure and social dysfunctions, but I’ll risk those and would rather deal with them as opposed to missing all the intellectual, material and emotional possibilities my fellow human beings can offer.

Ironically, people who feel lonely feel the most lonely when they are around other people. Loneliness is a state of mind first and foremost. It is a mental state in which you feel disconnected from the people around you which causes you to subsequently isolate yourself from them physically as well because it can be intensely painful to be with people. Being alone is almost always caused by feeling lonely.

Loneliness is usually caused initially by rejection or perceived rejection from others. If you were rejected a lot as a child, you can become overly sensitive and begin to see rejection in situations where you are actually accepted, in which case changing your state of loneliness can seem insurmountable. To complicate things further, people tend to instinctively shy away from people who isolate themselves so a great deal of real rejection is likely to be taking place as well.

Though it seems like it should be easy to simply change your state of mind, experience suggests those can be the most difficult changes we make. A lonely person has a long journey ahead of them if they desire to change. The first step, however, is accepting that it is first and foremost a state of mind and that it can be changed with a great deal of hard work. If you don't believe it can be changed, you won't be doing the work.

I've seen a lot of studies. If actuarial tables were more than just statistical probability, I'd already be dead.

Loneliness is part of the human condition. We can't eliminate it entirely, but certainly find ways to manage it. For me, it's a combination of being a better friend to myself as well as reaching out to others.

Lonliness is a state of mind, therefore you and only you can change it.

I do not like being alone,and being by myself let's the strange little beings inside my head out?

I agree with the comments below that you can do something about loneliness. They didn't mention that you can also do something about rejection. You can work on yourself. You can join groups where you have things in common with people and honestly get to know those people, not to try to get something out of them, but to enrich each other's lives. For example, if I constantly go after happily married men trying to get them to divorce their wives and marry me, I will be rejected. If I join a chess club, I will get to know nice people to play chess with. Then if I am positive and fun to play with, people will to get to know me. If I cry and complain every time I lose, no one will want to play with me.

We can all do something about loneliness by befriending and being kind to those whom we know of who are lonely. The problem is that we often don’t know, and can’t do anything to help, unless we ask them. Many people don’t express the fact that they are feeling lonely, maybe we need to ask people whom we suspect may be lonely, if they need anything and try to include them and encourage them to join in activities with others. There is a difference between being alone and being lonely, but I do agree that it is definitely a problem, especially amongst older people.

I agree loneliness is unhealthy. But why do you believe there is nothing that can be done about that?