Quality of life is a broad term without exact definition. It depends on a number of factors: support from friends and relatives, ability to work and interest in one's occupations, accommodation appropriate to expectations and, of course, health and disabilities whether congenital or recently acquired disorder. In the field of ill health physicians, by their training, concentrate attention on possible somatic disorder; the role of emotional disorder be it a reaction to the somatic illness or an independent factor, is often overlooked.

For instance pain from a disorder which was previously tolerable may become intolerable if a depressive state supervenes [1]; in another study [2] of patients who had undergone treatment for maxillo-facial cancer it was found that one in three had clinically significant anxiety and somatic symptoms were reduced by discussing the nature of anxiety and its possible manifestation as somatic distress.

Reasons for neglect to detect emotional disorder include the physician's lack of confidence in procedure for detection and sometimes a supposition that if it was discussed the patient may consider that his complaint was not being taken seriously. The fact remains that it is a frequent concomitant of somatic illness or that it may masquerade as somatic disorder [3–5]. A simple method for recognition of emotional disorder in the clinical setting will therefore be of help to the physician. Such information may be provided by a questionnaire which the patient may complete prior to examination.

The patients' own views are sometimes discounted yet Fallowfield [6] considered that the patient was the best judge of his/her own state. There may, of course, be situations in which the patient deliberately attempts to mislead the clinician by exaggerating the emotional element of his illness but this is not common; alternatively the emotional aspect may be suppressed if it is supposed that this will lead to a diagnosis of psychiatric illness. Any such questionnaire must therefore not only be brief and easily understood but should avoid reference to clearly abnormal perceptions (hallucinations) and such obvious implication of psychiatric disorder as suicidal inclinations.

A physician in general hospital practice said that he knew that a large proportion of patients attending his clinic were suffering from emotional disorder or else that such disorder was an important contributory factor to the distress of the illness. He pointed out that large numbers of patients precluded any attempt by himself to conduct enquiry into emotional aspects of illness but that he often felt that he was informing the patient inaccurately and perhaps, by stressing the role of somatic illness, aggravating the patient's condition. He asked whether there was a simple method, perhaps a questionnaire which the patient could complete whilst waiting to see him, which would be helpful. He added that questionnaires with a large proportion of their content devoted to somatic distress would not be useful; indeed one study [7] had demonstrated that any questionnaire purporting to provide information on emotional distress in dialysis patients but which contained a large proportion of items relating to somatic disorder provided misleading information. A review of the major existing scales was undertaken [8, 9] and the extent to which somatic factors, such as loss of appetite, would contribute to the score derived from completion. It was considered that most of the scales were either lengthy and required administration by a trained worker, or if short and designed for completion by the patient, did not appear to distinguish one type of emotional disorder from another. These observations led to the decision to design another questionnaire. It was agreed that, in order to make it short it should focus on the two aspects of emotional disorder which the clinician considered had most relevance i.e. anxiety and depression, that these two concepts be differentiated and that a scoring device provided which would give the best chance of reliable and helpful information of the sort which could be explained to the patient in the context of the disorder for which he was consulting the clinician.

Thought had to be given to the term 'depression'. Apart from the varieties of disorder subsumed under the term in the psychiatric lexicon it is used in everyday parlance for a variety of states of distress: demoralisation from prolonged suffering, reaction to loss [grief], a tendency to undervalue oneself [loss of self-esteem], a pessimistic outlook and so on. A questionnaire designed to cover all these concepts would be diffuse and probably fail to provide a clinician with useful information; it was therefore decided to concentrate on the loss of pleasure response [anhedonia] which is one of the two obligatory states for the official definition of 'major depressive disorder' and which, moreover, was considered by Klein [10] to be the best guide to the type of depressive mood disorder which may be considered to be based on disturbance of neurotransmitter mechanisms and therefore likely to improve spontaneously or to be alleviated by antidepressant medication; therefore the statements analysed for construction of the depressive component of the Scale were largely, although not entirely, based upon the state of reduced ability to experience pleasure, a typical statement being: "I no longer get pleasure from things I normally enjoy".

There can be no doubt of the need to assess the role of emotional factors in clinical practice. A brief questionnaire is provided for the purpose.

Many studies have confirmed the validity of the HADS in the setting for which it was designed. Other studies have shown it to be a useful instrument in other areas of clinical practice. Patients have no difficulty in understanding the reason for request to answer the questionnaire. It is available from a reliable publisher of psychometric scales; translations into many languages have been made and may be provided at request.