About this information
Mental health is a broad topic, and understanding some of the facts and figures associated with it can help to put individual experiences in context.
This information is targeted at mental health professionals, journalists and students. However, it is also our aim to present statistics in a way that makes this factsheet accessible to all those who are interested in mental health.
Note: The language used in these pages reflects the sources referred to. The use of such language does not imply Mind's automatic acceptance of it.
Understanding the figures
The frequency of mental health problems is well documented statistically. However, these figures need to be treated with some caution.
Often widely differing figures will be given for the same mental health problem, making it difficult to determine exactly how common it is. This is partly because these figures are not always measuring the same thing. For example, in order to reflect the fact that mental health is not fixed but likely to change over time, a variety of different figures are used. The most common are:
Prevalence: this measures the number of people with a particular diagnosis at a given time.
Lifetime prevalence: this measures the number of people who have experienced a particular mental health problem at any time in their lives.
Incidence: this measures the number of new cases of a particular mental health problem that appear in a given time period.
Often these figures are compared to provide further information about a mental health problem. For example, comparing the number of new cases, (the incidence) with the number who are ill at any one time (the prevalence) can give us a rough idea of the average amount of time a mental health problem is likely to last.
Another important factor is the kind of sample used to arrive at a particular figure. Often the number of people treated by health professionals is used to determine how common a mental health problem is. However, this is likely to ignore all those who have not come into contact with services. Furthermore, psychiatric diagnosis is often far from straightforward - a person's diagnosis may be changed several times in the course of their treatment. An alternative is to take a sample of the whole population and interview people, according to a standard set of criteria, to see if they have a mental health problem. This approach, known as a community survey, although expensive and time consuming, is usually the most reliable.