CDSM-IV axis II personality disorders involve ‘maladaptive personality traits’, such as obsessive–compulsive disorder. A study from Belgium reports no increase in such personality disorders in ME/CFS patients compared with people in the community (prevalence 16.3% in each group, in contrast with 58.7% in a comparison group of psychiatric patients). No surprise there then, particularly as the results accord with a previous study in 2009 (prevalence 12% in both patients and controls).

The interesting thing is that both of these ‘negative’ investigations used the ADP-IV questionnaire to assess personality disorder, whereas other ‘positive’ studies (reporting moderate differences between ME/CFS patients and controls) have tended to use the PDQ questionnaire which, as the authors point out, gives high rates of false positives and overestimates the prevalence of personality disorder. Such matters are important, particularly when the results of research studies affect the lives of real people, and impact on healthcare professionals’ views of the illness!

Reference: Prevalence of DSM-IV personality disorders in patients with chronic fatigue syndrome: a controlled study. Kempke S,et al. Int J Behav Med. 2013 Jun; 20(2): 219-28.