Set shifting in anorexia nervosa: an examination before and after weight gain, in full recovery and relationship to childhood and adult OCPD traits
Introduction
Anorexia nervosa (AN) may emerge as part of broad, genetically influenced phenotype encompassing various degree of rigidity, perfectionism and behavioural constraint. High levels of perfectionism and extreme compliance in childhood are specific risk factors for AN (Karwautz et al., 2001). Perfectionism and preoccupation with orderliness persist after recovery (Matsunaga et al., 2000; Strinivasagam et al., 1995). Furthermore, mothers of people with eating disorders have high level of perfectionism (Woodside et al., 2002). Perfectionism is one component of the broader categorisation of obsessive compulsive personality disorder (OCPD) which is increased in frequency amongst first degree relatives of people with AN (Lilenfeld et al., 1998). Another component of this categorisation of personality includes inflexibility or difficulty adapting to change, and preoccupation with details (Strober, 1980).
The neuropsychological deficits found in subjects with AN [for reviews see Braun and Chouinard (1992) and Lauer, 2002)] appear to mirror their behavioural and personality characteristics. For example, people with AN show specific sub-optimal performance on a variety of set shifting tasks in a laboratory setting (Tchanturia et al., 2001; Tchanturia et al., in press; Lauer, 2002; Fassino et al., 2002). These require the patient to shift between mental representations or response sets, and performance on them represents a form of mental flexibility. A preliminary investigation using two set shifting tasks found impairments in AN patients, but no difference between this patient group and an ANRec group suggesting long-term persistence (Tchanturia et al., 2002). This raises the possibility that this impairment in set shifting constitutes a marker of familial OCPD and is independent of the stage of illness.
The aim of this study was to undertake a more extensive analysis of executive task performance, associated with set shifting, in a larger sample of patients, in different stages of AN. It combines a cross-sectional approach, in which current patients are compared to a long term weight recovered and healthy control group, and includes a longitudinal design in which people are studied before and after weight restoration. The final aim was to examine whether these set shifting tasks were linked to behaviours characteristic of people with OCPD traits in childhood and in adult life. Our prediction was that deficits in set shifting represent an underlying vulnerability to compulsive traits which in turn predispose to obsessive compulsive personality disorder and AN, and that impairments in this function should persist after long term recovery.
Section snippets
Participants
Thirty-four patients were recruited from the South London and Maudsley NHS Trust. They fulfilled DSM-IV (Diagnostic and Statistical Manual, version IV, American Psychiatric Association) criteria for AN and were subdivided into n=20 with restricting type illness and n=14 with binge-purge type (in a preliminary analysis, the two types showed no difference in neuropsychological performance, and hence are collapsed in the subsequent analyses). These patients were tested in two days following
Cross-sectional data
In terms of demographic and clinical characteristics the only significant difference in baseline characteristics between groups was that current patients had lower BMI and higher scores on the MOCI and HADS (Table 1).
The means and group comparisons for set shifting tasks are presented in Table 2. The current AN group was significantly slower than other two groups on the Trail Making task, and performed less well than ANRec and HC in the Brixton test, picture set making, the perceptual shifting
Discussion
The main finding of the study is that not only did AN patients have sub-optimal performance in a range of set shifting tasks, but some of these impairments were also seen in people who had fully recovered from AN, implying that these are traits partially independent of current disease or nutritional status persisted after correction of the severe metabolic imbalance. Additionally, the study followed up patients in the AN group who achieved weight recovery after in patient treatment and found
Acknowledgements
The work was funded by The Welcome Trust-International Fellowship for Dr. K. Tchanturia (059049) and also from the European Commission Framework V program (http://www.cordis.lu/life/home.html) grant number QLK1-1999-916. The authors would like to thank Dr. Simon Surguladze and Prof. Iain Campbell for their help in this study.
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