Western culture, for good or ill, separates the mind from the body. Disorders of the body are left to medical science. But there is as yet no equivalent science of the mind. The 'metaphor' of mental illness is the best we can manage. People who become 'mentally ill' develop psychological problems which affect their emotional moods and behaviour, and the way they communicate with other people. Psychologists study mental life and behaviour; psychiatrists are doctors who specialize in treating disorders of the mind. They make a distinction between neurosis' and 'psychosis'. Neurosis is the name given to the more common and less serious types of mental disorder, like anxiety. Psychosis is when there is, at times, such severe distress that someone seems to lose touch with the familiar world altogether. Schizophrenia, for example, is a psychosis.

Schizophrenia does not mean 'split personality'; that is only one very rare form that this mental illness can take. There is no general agreement about schizophrenia's cause or cure, and some people even dispute that it exists. Yet one in every 200 people are diagnosed as having a schizophrenic illness at some point in their lives.

The condition results in a dramatic disturbance of thought and feeling. People start to experience the world very differently. They may come to believe that their thoughts, feelings and actions are under the control of an external force (thought disorder'). They may experience visions, seeing, hearing or even smelling things that others can't (hallucinations). They may be convinced of something for which there is no obvious justification - perhaps that they are being pursued by secret agents (delusions).

Periods of deep depression alternate with very excited behaviour (mania). During a manic or 'high' phase people are often very active, unable to sleep; they may spend vast amounts of money and see or hear things others can't. They may be irritable or talk so much they become incoherent. While 'low' or depressed they may feel overwhelmed by despair, guilt and feelings of unworthiness. They may become apathetic, unable to do even the simplest task.

Imagine you are about to be attacked. Your muscles tense in readiness for physical action. Your heart beats faster to carry blood to where it's needed. You breathe faster to get more energy. You sweat to keep your body temperature down. Your mouth becomes dry as your digestive system slows. Once the danger has passed you shake as your muscles relax. We have similar responses to a wide variety of experience, from talking to someone new at a party to taking an exam. Some people feel anxiety very often and very intensely. Sometimes a panic attack results: a pounding heart, sweating, chest pains, fast breathing and dizziness, combined with a fear of 'going mad' or out of control.

A very 'fashionable' complaint in Western culture at present, stress is one of the few acceptable' conditions we are free to admit to. We are even expected to have it. A 'stressful' job can be a status symbol. Its symptoms can include the loss of your sense of humour. But that doesn't make it any less serious or painful. It resembles anxiety in many respects but suggests that the causes are more rational and external than irrational and internal. To that extent, the present emphasis on stress may be an encouraging sign of a shift away from the 'personal pathology' of disorder.

Our reactions to the death of someone close to us are particular to us and to our relationship with them. But many people experience a sense of shock and loss. We may think we see the dead person walking down the street, or hear them calling our name. Despair, depression and anxiety are extremely common. We may surprise ourselves by feeling, say, anger and guilt towards the person we have lost. Sometimes, particularly if we lack the formal rituals of grief, the healing of the bereavement process gets stuck. We simply can't get back to living. We may feet we are expected to 'pull ourselves together' too quickly - or we may be unable to react to the death at all, even by crying. Grief can, and often does, transform people's lives.

The number of people so disabled by their distress that they have had to be cared for in institutions is relatively small. The vast majority are cared for by their own families and friends, often at enormous emotional cost. It can be as difficult for these carers to adjust as it is for the individual in distress.

The maintenance of mental health and the relief of distress depend on the attitudes of individuals, families, friends, whole societies. If we are conditioned by fear we make things worse: we get angry because we cannot understand, or else we pretend that the distress doesn't really exist.

All of us have a part to play. Support is not always as easy or as obvious a thing to give as we might like. For some distressed people any kind of heightened emotion, however 'supportive', can be destructive. We can't expect gratitude, any more than we ourselves would want charity from others. We have to learn what is appropriate to the particular individual in distress. That can be a hard, long struggle. But it is far better to face it than to run away.