Mental disorder and the strategies of prevention,

Prevention and health promotion are in the news. General practitioners in the UK must offer health checks or risk a financial penalty; 1993 will see the second World Congress of Preventive Cardiology; the Health Education Authority battles against smoking and AIDS; and so on in many branches of medicine but not in psychiatry. 'Preventive psychiatry' has not yet arrived. This is surprising, for psychiatry is confronted by many incurable patients and it was among the first specialities to embrance epidemiological research. Throughout medicine the understanding of prevention has been hindered by the tacit belief that disease and normality are separate entities. In psychiatry, whether the discussion is of Alzheimer's 'disease', depression or schizophrenia, the same question is asked, 'Has this patient got it? ', the answer being 'yes' or 'no'. Researchers, presented with a distribution of scores for the General Health Questionnaire (GHQ) or a depression inventory, hurry to apply an arbitrary cut-off point in order to separate those whom clinicians will accept as 'cases' from the remainder, who are grouped together as 'normals'. As Pickering (1968) wrote, 'Medicine in its present state can count up to two but not beyond'. No such separation really exists. As the old man remarked to his wife,' All the world is queer save thee and me, and even thou art a little queer'. In those few reports which do present complete distributions of scores for the GHQ, depression or dementia (Gurland et al. 1983; Brenner, 1985; Brayne & Calloway, 1988; Anderson et al. 1993) then-just as with IQ scores-they form a continuum. Case definitions are necessary wherever management decisions are dichotomous ('treat' or' not treat'); but they should be recognized for what they are, which is an operational convenience and not a description of nature. Disease comes in all sizes, and we should move away from asking 'Has this person got it? ' towards 'How much of it do they have? ' Recognition of the continuous distribution which unites the whole population, sick and healthy, is a first and necessary step towards rational prevention. The continuum between disease and normality is not readily apparent in hospitals and clinics, whose patients are the survivors of a selection process whereby only the more severely affected will be referred, thus creating an illusion of a qualitative separation of disease from normality. Patients in general practice have not been subjected to this process, and 'a touch of depression' is seen to be all too common. Awareness of the ' iceberg phenomenon' has stimulated enthusiasm for screening. This, however, is simply the pursuit of earlier diagnosis and it should not be confused with prevention. Clinicians find it natural to turn to the 'high-risk strategy' (Rose, 1985), which offers special support to the most susceptible or exposed individuals. This approach has been applied vigorously in cardiovascular disease through the identification and control of its various risk factors, and it has come to dominate the whole medical approach to prevention. Its purpose is to truncate the risk factor distribution by identifying and eliminating hypertension, drug abuse, criminal violence and so on, while leaving the rest of the population in peace. Such a truncation has never yet been achieved. The strategy could be compared with an attempt to control icebergs by sending warships to shoot off their visible portions, or with famine relief which feeds the hungry but does not tackle the causes of famine. The high-risk strategy provides succour for some needy individuals, but its