Depression is the commonest illness of all: 40% of the population will experience this condition at some time in their lives. It may be mild or severe. It can be a brief phase in someone’s life, or can lead to prolonged personal unhappiness, sometimes even to self harm or long-term disability. It is often associated with anxiety symptoms.

It occurs with many other physical illnesses, yet may sometimes pass unrecognized by doctors, families and even by people themselves. It can be difficult to recognize particularly when it occurs in childhood, postnatal or in later life.

Families of people with depression may have many concerns and questions about the condition which medical staff may find difficult to answer because of problems of time and issues of confidentiality.

Depression can present in many ways: it can mimic other medical conditions; it can appear associated with fatigue, stress, headaches, poor work or academic performance, marital difficulties, alcohol or drug problems, or for no obvious reason at all. Causes may be deep-seated – or sometimes surprisingly straightforward. It may present quite differently in those from other cultures.

Treatments include the ‘talking treatments’ (various types of psychotherapy) and medication. Both long-established and newly developed medications are effective, as is at least one alternative herbal remedy. None of these is without some side-effect. General practitioners treat most cases; but people who are more severely depressed may be treated by psychiatrists, in outpatient clinics or as hospital inpatients. However this illness affects you, a friend, or a member of your family, we hope that you will find something helpful in the following pages. We’ve used a wide variety of descriptions of depression, its causes and its best treatment, ranging from brain chemistry to social explanations. We have tried to include something for everybody.

Every human being has changes in their mood. Experiencing good, not so good, and low mood is normal. The variety of our feelings is essential to our being lively and responsive to our surroundings. We would otherwise be totally predictable and robotic. Contrasting moods and feelings add depth to our lives.

There will be times when elated, or extra good mood, is appropriate – something really good has happened and we are very happy. It will also be entirely appropriate to feel low, tearful and negative in other circumstances, for example being made redundant. The difference, however, between that experience and being depressed, can be subtle but all important. It is the difference between normal experience and illness. Many people would feel bad at losing a job but not everyone would go on to be ill. Illness begins and normal experience ends, at the point at which your everyday functioning is affected and continues to be affected beyond what would reasonably be expected. You would not expect a person who has lost their livelihood last week to be functioning well this week, but you would expect a gradual improvement over the course of the following months. If this (normal) mood is protracted and it starts to change the way someone is coping (or not coping) with life, it starts to become a problem or illness.

A very helpful definition of depressive illness was given by Sir Aubrey Lewis in the 1950s. He said depressed people are ‘sad, and ill with their sadness’ – this means not just low mood but, because they are ill, there are changes in the way their bodies are functioning. There can be a whole variety of symptoms, which we shall discuss later in the book, but there are common important changes that happen in clinical depression – or the illness depression. Sleep rhythms can be disrupted, and sleep can deteriorate badly. Depressed people often wake in the early hours of the morning and can’t get back to sleep again. Their appetite changes – it usually decreases with loss of weight, although sometimes, and less commonly, appetite increases (comfort eating). Concentration can deteriorate. Memory can be ‘fuzzy’.

Sexual interest often diminishes. Thoughts can be slowed down. These are all measurable changes and are signs of illness, rather than a simple, well circumscribed period of sadness.

Question: How common is depression?

Answer: Depression of one sort or another is the commonest illness of all; it’s said that 40% of all of us get this illness at some time in our lives. Nearly a quarter of all GP attendances are for some form of emotional problem; 3% of the population are estimated to be suffering from depression, and 8% suffer from mixed anxiety and depression, at any one time. Many more people, who don’t have a full-scale illness, have difficulties or disabilities owing to some depressive symptoms. There is a wide range of severity of this remarkable illness. It can range from a quite subtle loss of enthusiasm and pleasure in life, which is hardly even recognized by the person concerned or their family, to a severe condition that can need urgent hospital treatment for the patient’s safety.

Whole textbooks are written about the classification of different types of depression. The terminology can be very confusing.

Some of the headings that have been used include:

5.1 Primary and secondary depression