Motor disorders occurring in association with phenothiazine therapy have been widely appreciated and investigated since the advent of these drugs in the early nineteen-fifties. Published works have indicated that between 20 and 40 per cent of patients treated with phenothiazines exhibit signs of extrapyramidal dysfunction (Denham, 1961; Ayd, 1961). However, the relationship between treatment variables and the frequency of these motor disorders is not a simple one. Many factors are likely to have aetiological significance, and it seems that their occurrence is more a reflection of personal idiosyncrasy than of chemical structure, dosage or duration of treatment (Lancet, 1964).

It has been said that any drug which is active and produces an effect which is beneficial must also, under similar or different circumstances, have side-effects which are neither beneficial nor desired (Hamilton, 1965). It is the balance between desired and undesired actions which determines the usefulness of any drug. Such a balance varies according to the individual patient's needs. Thus a life-saving drug will be given even if it has serious side effects, while this would not be justifiable for a drug with only a marginally therapeutic effect. Scrutiny of past results may enable clinicians to make finer predictions as to which patient will benefit from a certain drug and which will suffer unacceptable side-effects. Phenothiazines are one group of drugs whose efficacies and dangers have been discussed in this way.

Hospital-treated parasuicides∗ have been studied intensively in recent years, and on the basis of these hospital studies aetiological theory is advancing and expensive endeavours in prevention are being put into operation. Yet hospital studies can be misleading because cases selected for admission may not be representative. This prospective survey, based on general practice in Edinburgh, was carried out to study the prevalences of parasuicide uncontaminated by factors influencing hospital referral.

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