2026 ECNP Congress

PS02-2082

Selective processing speed impairment in body dysmorphic disorder: a Wechsler Adult Intelligence Scale investigation

Katrina Holmes à Court — E. Byrne, R. Iyer, W.L. Toh, S.L. Rossell · Swinburne University of Technology, Centre for Mental Health, Hawthorn, Australia

2026 ECNP Congress

Body dysmorphic disorder (BDD) is a disabling psychiatric condition characterised by distressing preoccupation with perceived appearance defects, affecting approximately 2% of the general population [1]. Despite its severity, the neurocognitive profile of BDD remains poorly defined: previous studies have produced inconsistent findings, with reported deficits spanning processing speed, working memory, and reasoning [2]. A recent systematic review of 54 studies identified potential difficulties across multiple cognitive domains but noted that findings were limited by heterogeneous methodology and the absence of comprehensive, gold-standard cognitive assessment [3]. No study has used the most widely validated measure of adult intelligence , the Wechsler Adult Intelligence Scale, Fourth Edition (WAIS-IV)[4], to characterise cognition in BDD. This study aimed to establish a comprehensive cognitive profile of individuals with BDD using the WAIS-IV, and to determine whether any cognitive differences were independent of symptom severity and affective disturbance.

Fifty-nine adults with BDD (mean age = 32.66 years, SD = 9.66; 86.4% female) and 56 healthy controls (mean age = 30.27, SD = 11.13; 71.4% female) were recruited through a clinical trial in Melbourne, Australia. BDD diagnosis was confirmed via DSM-5 diagnostic module, with moderate-to-severe symptom severity required (Yale-Brown Obsessive Compulsive Scale Modified for BDD ≥ 20). Participants completed the WAIS-IV Australian and New Zealand edition, comprising four index scores: Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed. Group comparisons used Welch’s t-tests with Holm-Bonferroni correction, multivariate analysis of variance, and analysis of covariance controlling for general cognitive ability and affective symptoms.

The BDD group demonstrated significantly lower Processing Speed Index scores than controls (BDD: M = 89.69, SD = 14.00; HC: M = 99.18, SD = 20.15), d = −0.55, 95% CI [−0.92, −0.18], p = .016. Both contributing subtests showed medium-to-large effects: Symbol Search, d = −0.70, 95% CI [−1.07, −0.32]; Coding, d = −0.79, 95% CI [−1.17, −0.41]. Verbal Comprehension (d = −0.22), Perceptual Reasoning (d = −0.10), and Working Memory (d = −0.16) indices did not differ between groups. Processing speed deficits remained significant after controlling for general cognitive ability (p = .006) and affective symptoms (p = .008), and were unrelated to BDD symptom severity, insight, depression, anxiety, or selective serotonin reuptake inhibitor use.

These findings reveal a selective cognitive profile in BDD: preserved reasoning, verbal, and memory abilities alongside a specific reduction in processing speed. The independence of this deficit from symptom severity and mood suggests it may represent a stable cognitive characteristic rather than a secondary consequence of psychiatric distress. Slowed processing speed may reflect core features of BDD such as perfectionism and excessive attention to detail during timed psychomotor tasks. This cognitive profile has direct clinical implications for pacing psychological interventions and managing cognitive load during treatment, and highlights processing speed as a potential marker of cognitive vulnerability in BDD.

References

  1. Koran, L. M., Abujaoude, E., Large, M. D., & Serpe, R. T. (2008). The prevalence of body dysmorphic disorder in the United States adult population. CNS Spectrums, 13(4), 316–322.
  2. Malcolm, A., Brennan, S. N., Grace, S. A., Pikoos, T. D., Toh, W. L., Labuschagne, I., Castle, D. J., & Rossell, S. L. (2021). Empirical evidence for cognitive subgroups in body dysmorphic disorder. Australian and New Zealand Journal of Psychiatry, 55(4), 381–390.
  3. Holmes à Court, K., Malcolm, A., Toh, W. L., & Rossell, S. L. (2025). A systematic review of neurocognition and social cognition in body dysmorphic disorder. Australian & New Zealand Journal of Psychiatry, 59(3), 224–247.
  4. Wechsler, D. (2008). Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV) Technical and Interpretive Manual. Pearson.