Chapter 2 Child mental health and child mental health problems mental health problems
2.3 Classification of child mental health problems
2.3.2 Implications for establishing the validity of psychiatric classes classes
Building a case for validity
The development of agreed diagnostic schemes and clearly-defined criteria for child mental disorders has played a crucial role in increasing inter-practitioner reliability and inter-study comparability [167]. Nevertheless, basing classification upon observed symptoms rather than upon underlying pathological mechanisms raises important difficulties for establishing the validity of psychiatric classes. Not all children have all symptoms, creating the problem of how much variation is permissible within the ‘same’ class. Conversely, many children have symptoms from across two or more nominally different classes. This creates controversy as to whether a classification system is adequate or whether it should be modified by, for example, combining classes together or proposing alternative categorisations.
45 It will rarely be possible to resolve these issues definitively. Instead one needs to build a case for the validity of a particular system by, at a minimum, showing that the proposed symptoms do cluster together and are associated with negative impact. When proposing new psychiatric classes, it is also necessary to justify those classes as making useful predictions about external factors such as differential prognosis or treatment response [167]. Some flexibility in operationalising classes is also common, as exemplified by criteria requiring a minimum numbers of symptoms from a list and by the existence of Not Otherwise Specified categories (see Box 2.3, p.43).
The need to re-establish validity in all new populations
The phenomenological approach means that the case for validity rests not upon generalisible understandings of disease mechanisms but upon observations of symptoms and impact in particular populations. There may therefore be no classification system which is uniquely best or universally applicable. For example, symptoms which fall into separate clusters in high risk populations may form a single cluster in low-risk populations.
This seems to apply to adult emotional problems, with the distinction between depressive and anxiety symptoms being far more apparent in clinic than in community settings [173].
Symptom-clusters may also differ across social or cultural populations such that classes are meaningful in some populations but not others. This possibility forms the basis for the relativist critique of the universalist approach to cross-cultural psychiatry. The universalist position stresses the shared features of mental health problems and disorders in different populations and seeks to study these using a single standard framework [78, 174-175].
This ‘etic’ approach underpins most psychiatric epidemiology and lies at the heart of diagnostic classification systems like DSM-IV [176]. Yet DSM-IV largely developed through European and North American input [177], and has been criticised for showing Euro-centric bias [178-180]. Most dimensional questionnaires and empirically-derived symptom structures were likewise developed in Western populations.
The relativist critique highlights the danger of assuming that these Western-derived classification systems will apply universally. One central tenet of the relativist position is the importance of considering ‘emic’ mental health phenomenology, namely that which is
46 meaningful within any particular culture [181-182]. A second tenet is that illness experiences in different cultures may be so different as to represent genuinely separate conditions. Applying nominally etic classification systems therefore risks committing the
‘category fallacy’ of carving up the mental health landscape in a way which lacks face validity and coherence [14, 181, 183-184].
In thinking about category fallacies, I believe distinguishing face validity and coherence is crucial. ‘Face validity’ category fallacies correspond to the relativist concern for emic understandings, and occur whenever a particular construct does not map onto a locally meaningful category. This would certainly represent grounds for caution, but would not necessarily prevent meaningful cross-cultural comparisons or the useful application of insights about aetiology, prognosis or treatment. For example, in rural Uganda no local concept maps straightforwardly onto the English term ‘depression’. This did not, however, prevent the DSM–IV criteria for major depressive disorder being used to identify adults who were successfully treated with interpersonal psychotherapy [185].4 So long as similar constellations of symptoms exist in different populations, I believe it may be possible to apply etic classifications in a meaningful way. By contrast, ‘coherence’ category fallacies occur if symptoms show fundamentally different patterns of association in different populations. This form of category fallacy is the more serious threat, as it renders comparisons genuinely meaningless.
Finally, the centrality of negative impact to the definition of mental health problems or disorders means one must also remember that a given symptom-cluster may be a ‘problem’
in one population but not in another. For example, one might identify a population in which a comparatively high proportion of children displayed the core symptoms of hyperactivity (e.g. restlessness and short attention span), but where this did not cause them distress or impairment. It might certainly be of interest to study hyperactivity symptoms in that population, not least to investigate factors which were protective against negative
4 This issue also applies to physical illnesses. For example, early on in the HIV/AIDS pandemic before a blood test was available, HIV/AIDS was diagnosed based on clinical symptoms and signs. Most of these were derived from observations in the USA, and HIV/AIDS certainly lacked face validity in many Sub-Saharan African settings which had no equivalent in their lexicon or nosology.
47 impact. In the absence of such impact, however, it would not be appropriate to consider hyperactivity as a highly prevalent mental health problem in that particular population.
Cross-cultural category fallacies as an instance of a more general challenge in psychiatric epidemiology
Criticism of the universalist approach as an unexamined default position has mainly occurred within the field of cross-cultural psychiatry. Yet demonstrating that proposed psychiatric classes are internally coherent and reduce well-being is crucial in any population. Likewise, establishing the comparability of the constructs under consideration is essential for meaningful comparison across any populations, including across time, space or social group. Moreover, there are no absolute criteria for deciding how much variation between populations is permissible before a category fallacy occurs. This has strong parallels with the difficulty of deciding how much variation between children is permissible within the ‘same’ disorder.
I therefore believe that the relativist critique is closely linked to a central challenge in all psychiatric epidemiology, namely the need to build a case for the validity of any classification system in any population to which it is applied. In the next section I discuss the evidence on this issue for the broad domains of common child mental health problems which I use in this thesis. In doing so, I first present evidence from the UK and similar settings and then discuss how far this is replicated in other cultures. Because little has been published regarding children from different ethnic groups in the UK, I instead draw upon the wider cross-cultural literature.