There are some physical complaints that simply cannot be medically explained. And there are some illnesses that are triggered or worsened by factors that happen entirely in the mind. In fact, your stress, anger or depression could be dangerously damaging your body right now, without you even knowing it.

Your psychological state impacts on the way your body functions. In other words, many illnesses are psychosomatic – they involve the mind’s reaction (psyche) to the physical (soma) illness.

Severe stress, for example, can cause nausea, abdominal pain, hair loss, chest pain, diarrhoea, giddiness and muscle pain. Illnesses like ulcers, irritable bowel syndrome, high blood pressure and heart attacks are all strongly influenced by psychological factors.

Not convinced? Read on…

Happiness

Research has shown that people who are happy, lively and calm are less likely to become ill when they are exposed to a cold virus. And, when they do come down with a cold, happy people experience fewer symptoms than average.

"We need to take more seriously the possibility that positive emotion is a major player in disease risk," says US Carnegie Mellon University Psychology Professor Sheldon Cohen.

Happy people are also less likely to develop heart disease. The reason may have something to do with serotonin, a chemical in the brain that regulates mood and is linked with happiness. A less active brain serotonin system is associated with early hardening of the arteries, according to several studies.

Happiness also prevents age-related disorders like Alzheimer's disease and arthritis. Research has found that women who are actively and positively engaged in their lives have lower levels of harmful IL-6 chemicals in their blood.

Kindness

People who offer love and help to others may be rewarded with better mental and physical health themselves, according to several studies. And people who volunteer actually live longer.

"People who volunteer frequently live longer than people who never volunteer,” says US researcher Dr. Alex Harris. “The volunteering-longevity association remained significant even after controlling for important factors, such as health status, social support, and physical activity."

Self - belief

Believing that you can do something will actually help you to achieve it, and that’s not only because you are more likely to be proactive and reach for your goals. For example, people who believe they have the capability to stick to the regimen required to control their Type I diabetes have better blood sugar control than those who don’t. Evidence that beliefs are strong predictors of health and behaviour and, therefore, clinical outcomes.

Depression

It is well known that depression and hostility significantly increase your chances of suffering from heart disease and heart attacks (Read more: Depression Increases Heart Failure Risk).

This may be because even mild to moderate levels of depression or anger make you five times more likely to have raised levels of IL-6, a protein that is associated with clogged arteries and a greater risk of heart attack. Depressed people are also four times more likely to suffer from hypertension (high blood pressure).

Further research suggests that people who experience an increase in hostile feelings from their late teens to their late 40s double their risk of heart disease.

“The findings suggest that men who exhibit hostility and depressive symptoms, even in the mild to moderate range, are at heightened risk for cardiac events," said Dr Edward C. Suarez of Duke University Medical Center.

Depression also plays a role in a person’s recovery after surgery. Studies have shown, for example, that recovery after coronary artery bypass surgery depends as much on the patient's state of mind as it does on the condition of the patient's heart.

In fact, depressed patients are more than three times more likely to experience a cardiac problem like heart failure or a heart attack within the next year.

Women are more likely to experience problems, with almost half of the depressed women experience further serious cardiac issues within a year after surgery.

"We looked at many factors, including the patient's age, gender, marital status, smoking behaviour, and depression," said US researcher Dr. Connerney, "but it turned out that only depression, heart condition, and gender mattered, and they were of equal importance."

Depression can also eat away at a person’s long-term cancer survival. Researchers have found that people's lives are more likely to be cut short when they had more symptoms of depression.

"We're trying to understand the role of the mind in the disease process,” says US University of Rochester psychologist Kirk Warren Brown. “The findings suggest that a truly interdisciplinary approach to treating the patient as a whole person is essential.”

Read More: to find out about the effects stress and loneliness have on your health, Click Here.