Stress

There’s a well-known deadly link between stress and heart disease. The psychological distress leads to a number of changes in body composition and metabolism that are well-established risk factors for heart disease.

Eventually, these changes in body composition and chemistry — known collectively as the metabolic syndrome — produce heart disease.
Researchers have found a direct, immediate relationship between distress and metabolic syndrome, as well as an indirect, delayed link where distress promotes poor health habits that, over time, exacerbate metabolic syndrome.

Stress also increases the risk of heart disease even for young women, and there’s a medical explanation why: women have traditionally been considered "immune" to heart disease until after menopause, when their oestrogen levels dramatically drop. Oestrogen produced before menopause helps protect against heart disease and osteoporosis.

But stress can actually reduce oestrogen levels much earlier in life and quadruple the early development of hardened arteries that cause heart attacks and strokes.

"Stress during the years before menopause can lead to the early development of hardened arteries," says Dr Jay Kaplan of Wake Forest University in the US. "This suggests that having an oestrogen deficiency in the pre-menopausal years predicts a higher rate of heart disease after menopause."

Research has also shown that stress plays a significant role, and may be the primary cause, in chronic fatigue syndrome – a debilitating fatigue that can include muscle aches, fever and sleep disturbances. Its cause had not previously been understood.

One study has even shown that stress kills off new nerve cells in the brain. (Read more: Stress Can Kill Brain Cells).

Loneliness

Studies show that lonely people have a greater risk of heart disease, and it’s due to differences in how their cardiovascular system reacts in times of stress rather than because of unhealthy behaviours.

When performing mentally and emotionally stressful tasks, lonely people experience increased blood pressure due to a harmful increased resistance to blood flow, and they develop higher blood pressure in the long run – and this is not linked to behavioural risks. Both chronically high blood pressure and vascular resistance have been linked to increased risks of heart disease.

Studies have also shown that lonely people experience less restorative sleep.

Having social support to combat loneliness improves general health, contributes favourably to the body's immune system as well as cardiovascular and hormonal functions, and even impacts favourably on the ageing process.

Studies people with a wide network of friends are considerably less likely to be affected by a broad range of biological risk factors for disease and death.

“Relationships affect a range of biological systems, since emotional experiences are translated by the brain into physical wellbeing,” says researcher Dr Teresa E. Seeman.

She says that the mind’s effects on the body are evident throughout life, with significant effects on health and ageing.

But if you don’t have a fabulous social network, don’t panic – research has also shown that pets are as effective in keeping blood pressure down as human contact is.

"Elderly women living alone who are attached to their pets and have nobody else derive physical benefits that are similar to those derived from human companionship," says research scientist Dr Karen Allen.