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Professor Rutter’s account of the issues involved in making diagnostic schemes is characteristically authoritative and lucid (Rutter, 2011). It deserves the careful attention of everyone involved in the current revisions for DSM-V and ICD-11, and indeed of everyone involved in the clinical use of diagnoses. My purpose here is to obscure some of the clarity and explore the implications of what seem to me the most controversial points.

Diagnostic classification is not only an administrative necessity: it conditions clinical thought. A certain circularity develops. One may require, as the DSM revision does, that diagnostic entities should only change when evidence appears; but that evidence does not appear because research is based on the existing entities. At each revision of DSM similar issues have been emphasised as needing research; the research did not materialise; and the issues were brought back again (Shaffer et al., 1989). Should there, for instance, be a separate category of attention deficit without hyperactivity? It appeared in DSM-III, disappeared in DSM-III-R, appeared again in DSM-IV, and is a current item of controversy. It has been difficult to mount research studies on conditions that are not officially recognised.

‘Symptoms’ and ‘impairment’

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References

It may be because of this conceptual limitation imposed on research that we do not know enough about the relationship between ‘symptoms’ and ‘impairments’. If impairment of function is a necessary condition of making a diagnosis, difficulties and contradictions follow. It becomes hard to diagnose a case when the individual has triumphed over the adversity; it discourages prevention before impairment has appeared (though an ‘at-risk’ qualification could be developed); it can be difficult (but not impossible) to determine which components of a complex presentation are responsible for impairment. Impairment is influenced by all kinds of external influences that are independent of the disorder. A supportive school, a resourceful family or a high IQ will influence function and should not be confounded with psychiatric symptoms. This complexity has confounded the diagnosis of attention deficit/hyperactivity disorder (ADHD) in adults. An onset before the age of 7 has been a diagnostic criterion, but does not seem to be valid in the retrospective accounts of adults (Faraone et al., 2006). The confusion arises in part because the presence of symptoms in childhood has not necessarily led to impairment – and so a diagnostician may falsely conclude that there was no childhood problem. The draft for DSM-V has now clarified that an origin in childhood can be made on the basis of symptoms alone.

Should impairment ever be a criterion for diagnosis?

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References

Rutter makes a strong analogy with conditions in physical medicine to argue against including disability or impairments as criteria (Rutter, 2011). It would indeed be absurd to consider that a person whose diabetes is well controlled does not have the disease. On the other hand, the comparison with diabetes emphasises a problem for psychiatry: we have, as yet, only a rudimentary understanding of pathophysiology, and we lack objective measures such as glucose tolerance. Many psychiatric conditions behave as continua in the population. As a result, cut-offs are often arbitrary, reliability is low around the point of cut-off, and there is scope for a runaway expansion of diagnoses (as in the massive increase of bipolar disorder in a decade; Moreno et al., 2007). In the absence of cut-offs with a good biological validation, it has been logical to set the threshold at the point that predicts impairment, now or later. This happens in physical medicine too: the threshold for hypertension is the 95th centile, because that best predicts the risk for heart disease and stroke and indicates the need for treatment. Admittedly, this use of impaired function is at the group level rather than a requirement for each individual case. In child psychological disorders, however, the relation between symptoms and disability is rather weak (Angold, Costello, Farmer, Burns, & Erkanli, 1999). Harmful dysfunction remains a useful way for clinicians to think about individual cases.

The groups working on criteria for disorders such as ADHD and autism spectrum have, so far, found it hard to fix cut-offs for a diagnosis without including a requirement for dysfunction. As Rutter himself comments, the situation of people with an Asperger pattern of symptoms but good psychosocial function may make a diagnosis offensive. Furthermore, to expect extra school resources on the basis of symptoms alone could be wasteful and unacceptable to schools. Similarly, people with subthreshold symptoms who are nevertheless impaired should not be denied service. The revision of diagnostic schemes gives a strong impetus to develop better understanding about the relationship between symptom and function for each disorder.

To make matters more complex, the distinction between symptom and function is sometimes obscure in psychiatry. The diagnosis of ‘intellectual disability’ does, obviously, imply some impairment of adaptive social function. Impulsive errors in schoolwork can be both a symptom and a disability.

Impairment is, in short, more deeply involved in the definition of disorder than is often allowed. At the individual level, it seems best to be clear about the distinction between symptom severity and impaired function, but to be careful to include both in clinical thinking, to be rigorous about both, and sensitive in the way they are communicated.

Scientific and vernacular language

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References

The language of classification needs to be pragmatically effective. Care needs to be taken about the naming of conditions and the impact on public understanding. ‘Temper dysregulation’– a new condition in the draft for DSM-V – could well be perceived as an attempt to pathologise normal anger. More controversially, ‘callous-unemotional’ is a phrase both in the research literature and in the vernacular, but with somewhat different overtones. The moral implications of the common language words might lead to harsh attitudes or nihilism towards those affected. I believe that teachers are sometimes led by the words to confuse the cognitive inability of people in the autism spectrum with the more emotionally based failing of empathy in those with psychopathy. Research on the impact of medical terms on the attitudes of patients, caregivers and teachers would be feasible and useful.

Disorders across the age span

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References

Most psychiatric disorders begin in childhood or adolescence, and a move towards disorders across the age span (rather than ‘disorders of childhood’) is welcome. The attendant risk, however, is that childhood problems may be mislabelled as the beginning of an adult disorder. The antecedents of schizophrenia (such as bizarre thinking and motor changes) may indeed be detectable in childhood – but they may be the antecedents of other conditions too, or transitory states, and labelling as ‘at risk for psychosis’ could do more harm than good. General as well as specific risks need to be codable in the present state of knowledge.

Categories and dimensions

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References

Broad, simple categories to guide primary care are essential. They do, however, need to be narrow enough to guide the course of referral and act as effective triage. ADHD, for instance, would need separation from oppositional problems – not because of fundamental brain differences (though they may well be present), but because a service including medication will be desirable at an earlier point than would be the case for non-hyperactive conduct problems.

The broad categories then need to be supplemented with dimensional descriptions of the differing components. For instance, a diagnosis of autism spectrum should not be allowed to obscure the possibility that ADHD or obsessive-compulsive disorder is also present and treatable. They will better be seen as components of complex disorder than as separate diseases (‘comorbidity’). Irritability and defiance, as components of oppositional disorder, have different courses (Stringaris, Cohen, Pine, & Leibenluft, 2009). They occur together too often for separate diagnoses to be sensible, but their recognition as dimensions, with quantifiable severity, will be a real help to clarity in clinical thinking. The challenge, for the revisers of the diagnostic schemes, is to develop workable and economic descriptions.

References

  1. Top of page
  2. ‘Symptoms’ and ‘impairment’
  3. Should impairment ever be a criterion for diagnosis?
  4. Scientific and vernacular language
  5. Disorders across the age span
  6. Categories and dimensions
  7. Correspondence to
  8. References
  • Angold, A., Costello, E.J., Farmer, E.M., Burns, B.J., & Erkanli, A. (1999). Impaired but undiagnosed. Journal of the American Academy of Child and Adolescent Psychiatry, 38, 129137.
  • Faraone, S.V., Biederman, J., Spencer, T., Mick, E., Murray, K., Petty, C., et al. (2006). Diagnosing adult attention deficit hyperactivity disorder: Are late onset and subthreshold diagnoses valid? American Journal of Psychiatry, 163, 17201729.
  • Moreno, C., Laje, G., Blanco, C., Jiang, H., Schmidt, A.B., & Olfson, M. (2007). National trends in the outpatient diagnosis and treatment of bipolar disorder in youth. Archives of General Psychiatry, 64, 10321039.
  • Rutter, M. (2011). Child psychiatric diagnosis and classification: concepts, findings, challenges and potential. Journal of Child Psychology and Psychiatry, 52, 647660.
  • Shaffer, D., Campbell, M., Cantwell, D., Bradley, S., Carlson, G., Cohen, D., et al. (1989). Child and adolescent psychiatric disorders in DSM-IV: Issues facing the work group. Journal of the American Academy of Child and Adolescent Psychiatry, 28, 830835.
  • Stringaris, A., Cohen, P., Pine, D.S., & Leibenluft, E. (2009). Adult outcomes of youth irritability: A 20-year prospective community-based study. American Journal of Psychiatry, 166, 10481054.