Stress is not a mental illness in itself. Some degree of stress is an inevitable part of life and all significant changes may be stressful. It is how we handle stress that dictates whether the result is mental distress.

Stress is a two-part process: firstly, life throws an unusual challenge in our path (the stressor) and then our minds and bodies cope with it in a characteristic way (the stress response).

One of the best descriptions for exactly what stress does to the body and how it works is contained in Paul Martin’s The Sickening Mind, which is an examination of how psychological stress and disease interact and reinforce each other. Martin defines stress as:

“The state arising when the individual perceives that the demands placed on him exceed (or threaten to exceed) their capacity to cope, and therefore threaten their wellbeing.”

Stressors can be physical or psychological; physical ones include injury, disease, surgery, undernourishment and extremes of pain, heat or cold. However one of the reasons stress in modern-day society often results in distress is because most of the stresses of modern life are psychological; we are more likely to encounter an unreasonable boss than an enemy in battle.

Stress elicits a characteristic response in the body, called the startle response. Within a few seconds the autonomic nervous system fires and causes the hormone epinephrine (adrenaline) to flood the system. This increases blood flow to the muscles and away from the skin and digestive system. It dulls pain and dilates the pupils of the eyes (hence the pale skin, wide eyes and ‘butterflies in the stomach’ of fear).

Prolonged stress – lasting longer than a few minutes – causes a different part of the nervous system to send a second hormone, cortisol, to course through the body. Cortisol does two things: it turns the body’s energy reserves into glucose for immediate use, and it dampens down the immune system.

The reason it acts on the immune system is in order to delay the inflammatory response that the body uses to direct the immune system to the site of injuries; cortisol enables us to ‘keep going’ when otherwise we would be sick from the effect of immune system chemicals (cytokines), which cause the characteristic symptoms of infection such as fever and aches. This is the reason why many people soldier on through stressful work then get sick as soon as they go on holiday. Artificial versions of cortisol – corticosteroids – are used medically to damp down inflammation in the same way.

The problem with long-term stress is that the immune suppression can make us sick eventually anyway.

By correlating stressful events in people’s lives with subsequent sickness, psycho-immunologists have been able to devise a stress scale which predicts the amount of stress specific events may cause an average individual. Here are the Top Ten:

Note that positive events are stressors too. And note how many events (death of partners, separation, serious illness, job loss) may be events typical of a life lived with HIV.

Fight, flight or freeze

The autonomic nervous system has two arms – the sympathetic and parasympathetic nervous systems. The job of the first is to produce the startle response and get the adrenaline going. The second is to do the opposite: by direct nerve signals and by releasing the hormone acetylcholine (alongside others) it causes the blood to flow back into the skin and away from muscles, gets digestion going again, and brings down the body’s energy level. These two systems are complementary, like paired muscles that extend and flex joints. However they are not a zero-sum game: they may both be firing at once. For instance, the parasympathetic system causes erection by releasing blood to the penis; the sympathetic causes orgasm by contracting the genital muscles.

The purpose of adrenaline is to cause the individual to either fight the stressor or to flee from it. However, if the stressor can neither be defeated or run away from, a third way of handling stress comes into play – the freeze response, characterized by animals that ‘play dead’ when confronted by an attacker. What happens is that even while the sympathetic nervous is still firing the parasympathetic overrules it and paralyses the muscles.

Simplistically speaking, if the freeze response happens in response to a stressor, and particularly to long-term stress, mental distress is much more likely to result. Studies have shown that people who respond to an attack or a disaster by fighting the aggressor or running away are much less likely to suffer depressive or anxiety symptoms than people who freeze in terror. One of the reasons child abuse is so damaging is because children are not in a position to fight or flee.

When the ‘freeze’ response takes over, the result is dissociation – a feeling of unreality and detachment. The person, deprived of the ability to run away in reality, ‘runs away’ from the event internally. “It seemed so unreal,” or “It was like it was happening to someone else,” people will say. Unfortunately this also means that clear memories of the event fail to be laid down. It is believed that deprivation of a ‘narrative’ – a sequential memory of a traumatic event – is the cause of post-traumatic stress disorder, as it means the event is not placed by the brain where it belongs in time and therefore the unconscious mind still reacts as if the event were happening now.

Some stress is good for the system; the result otherwise is boredom, which is stressful in itself. This is the reason people go to roller-coaster rides and horror movies. The key difference between helpful and harmful stress is control. A work assignment may be daunting but if the individual believes they can accomplish it, they will do. Complementary therapies may help people suffering from chronic illnesses because they help the individual feel in control of the disease.

The freeze reaction, if long-term stress keeps it going, may result in two types of mental illness – the two most common types. If the parasympathetic response predominates, the result is depression (which is why depression is sometimes called ‘learned helplessness’). If the sympathetic response does, the result is anxiety. Both may happen at the same time – and often do.

Further reading

Martin Paul. The Sickening mind – Brain, Behaviour, Immunity and Disease. Flamingo, 1997. ISBN 0 00 655022 3