The paper reviewed here is ‘Development of Criteria for a Diagnosis: Lessons from the Night Eating Syndrome’ by Stunkard and colleagues. The authors of this paper argue for the inclusion of a syndrome ‘Night Eating Syndrome’ (NES) in DMS-V. DSM-V, although not yet published, has already produced a lot of interest. Many groups recognise this as an important time to influence the classification of mental illnesses. In their abstract, the authors conclude by writing that
‘..research on NES supports the validity of the diagnosis and its inclusion in DSM-V‘
So the question to ask on reviewing this paper is ‘Do the authors justify their conclusions?’.
The authors begin by quoting Blashfield et al’s 5 criteria for inclusion in DSM-IV. As I wasn’t familiar with Blashfield’s work I performed a quick internet search and found that he is a Professor of Psychology who has a particular interest in diagnostic classification. He was part of the working group for Personality Disorders in DSM-IV. He’s written a number of papers on diagnostic classification and has developed evident expertise in this area. Blashfield’s criteria are 1. ‘There should be at least 50 journal articles on the proposed diagnostic category in the last 10 years….’ 2. Diagnostic criteria should ‘include self-report measures, structured interviews and rating scales’ 3. ‘There should be at least 2 empirical studies by independent research groups demonstrating high interclinician correlations’ 4. ‘The proposed category represents a syndrome of frequently cooccurring symptoms, described in at least 2 independent studies’ 5. ‘There should be at least 2 independent empirical studies showing that the proposed category ” can be differentiated from other categories with which it is likely to be confused’.
Before looking at how the authors have addressed each of these 5 criteria, how useful are these criteria? Turning to the first point – ‘there should be at least 50 journal articles’ – this seems like an arbitrary number. Why not 100 or 25? Does it matter which journals the articles appear in? What kind of articles should they be? Do editorials count? or reviews? or letters? The qualifier that they should be ‘in the last 10 years‘ also raises other issues. This qualifier means there should be, on average, 5 papers a year for those 10 years. Practically speaking there are going to be certain people or groups that are interested in specific syndromes. If this is so, then it would mean that they would need to have a high and consistent output for at least 10 years in the area of the syndrome. If they wanted the syndrome of interest to make it into DSM they would need to adopt a long-term perspective with sustained investment of (probably) significant resources. This means that there would be a 10-year delay before new diagnoses make it into DSM and if you add the time between publication of DSM editions this could be up to 15 years. This means that people may not have commonly agreed diagnostic criteria for well over a decade and may use alternative diagnostic criteria. Within the dementias for instance, Lewy Body Dementia is one diagnosis that has more recently emerged and would benefit from the support of diagnostic classificatory systems such as ICD and DSM.
Turning to point 2, this seems entirely reasonable. The aim here presumably is to triangulate the evidence base for the diagnosis and it could be argued that this should be taken even further. Point 3 raises similar issues to point 1. Why the choice of 2 empirical studies? Surely there is a more subtle use of the empirical data which could be used in place of this. Although they refer to interclinician correlations perhaps a reference to construct and face validity might be more useful or instead of 2 empirical studies – a threshold value for inter-rater reliability. Point 4 also makes reference to 2 studies while also referring to ‘frequently cooccurring symptoms’ which is a defining feature of a syndrome – a symptom cluster. Finally Point 5 refers to the differentiation from other categories. It can be argued that this is a very useful feature as ideally it would mean that syndromes included in DSM should have little diagnostic overlap. However, many illnesses do have an overlap and the distinguishing features may take a while to emerge offering another perspective on cross-sectional empirical studies which demonstrate good diagnostic separation.
Even though these shortcomings can be raised, there has to be a starting point. The authors proceed to work through each of the criteria showing how the data has been accumulated to satisfy most of the points. The diagnostic criteria are described thus
‘1. evening hyperphagia (the consumption of at least 25% of daily food intake after the evening meal)
2. three or more nocturnal awakenings with ingestions per week, or
3. both behaviors (1 and 2)’
On the third point however they recognise a need for multicentre trials with independent investigators demonstrating good inter-rater reliability. They then add some supporting features for the diagnosis. They argue that it may act as a ‘pathway to obesity’ and that there is ‘psychiatric comorbidity’. In this regards I was intrigued to see an associated with ‘depressed mood’ but the authors note that
‘many night eaters become more depressed in the evening‘
I presumed that they italicised the word ‘more’ in order to distinguish it from the low mood that is characteristically described in the morning in depression. If this is the case, then it should be noted that the diurnal mood variation described in depression is characteristically described in the mornings but can occur in the evenings also – the important feature is that there is a consistent change in mood. So the next question to ask is ‘Can night eating form part of the clinical picture of depression?’. If it can then that has implications both for depression and for the night eating syndrome. There are further arguments in support of the diagnosis including features of the circadian rhythm.
I would be more convinced if there were substantial arguments to distinguish this syndrome from ‘healthy behaviour’. ‘Healthy’ might not be the right word here but what I mean by this is why does someone getting up at least 3 times a week and eating constitute an illness behaviour? I think it is reasonable at this stage of an illness construction to provide arguments to distinguish this ‘syndrome’ from healthy thoughts, feelings and behaviours. People might for instance wake through the night for other reasons and the eating becomes associated with this period of wakefulness.
The ‘midnight snack’ in the UK became a cultural icon occurring in clever marketing campaigns for certain drinks, foods.
The R Whites campaign even won an international award for their campaign in the early 70’s. The authors also show that the SSRI’s can be useful in managing this syndrome and this emphasises the importance of distinguishing this from healthy behaviours.
While the authors provide lots of supporting evidence, it is precisely at this stage that the diagnosis needs to be examined critically and wider dialogue engaged in.
Stunkard A J et al. Development of Criteria for a Diagnosis: Lessons from the Night Eating Syndrome. Comprehensive Psychiatry. 50. 2009. 391-399.
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