Improving the identification and treatment of co-morbid depression and/or anxiety in adolescents with Chronic Fatigue Syndrome (CFS/ME)

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)



Many common mental health problems, including depression and anxiety, first emerge in adolescence. Prior work has found evidence of elevated depression and anxiety in samples of adolescents with chronic fatigue syndrome (CFS/ME). However, this has been based on gold standard diagnostic interviews in small, self-selecting samples which may be biased or on screening questionnaires in larger, more representative samples which may be affected by symptom conflation and have not been validated for use in this population. Furthermore, few studies have investigated the prevalence of both depression and anxiety concurrently in the same adolescents with CFS/ME.
Some adolescents with CFS/ME may be more likely to have co-morbid depression and/or anxiety than others and their outcomes may be different. Identifying the demographic and clinical characteristics of those who are more likely to have co-morbid depression and/or anxiety would enable selective, targeted screening and monitoring. Negative thinking patterns are a malleable perpetuating factor in depression and anxiety. Understanding how the general and fatigue-specific negative thinking patterns of those adolescents with CFS/ME and co-morbid depression and/or anxiety compare to those with CFS/ME only would inform treatment targets. Comparing outcomes at 6-month follow-up for those with co-morbid depression and/or anxiety to those with CFS/ME only is an important part of determining whether treatments for both CFS/ME and mental health problems need to be adapted.
My programme of work aimed to improve the identification and treatment of co-morbid depression and/or anxiety in adolescents with CFS/ME. I conducted 3 empirical studies and used the findings to inform the development of an adapted treatment for this subgroup.


Study 1: Cross-sectional clinical study using gold standard semi-structured diagnostic psychiatric diagnostic interview and screening questionnaires, N = 164 adolescents (age 12 to 18) with confirmed CFS/ME.
Study 2: Longitudinal study, 3 clinical cohorts, using questionnaire data (demographics, fatigue, functioning, depression, and anxiety symptoms) at baseline (initial clinical assessment) and 6-month follow-up, N = 490 adolescents (age 12 to 18) with confirmed CFS/ME.
Study 3: Cross-sectional study nested within the baseline of a randomised control trial, using questionnaires (depression and anxiety symptoms, general negative thinking patterns, fatigue specific thinking patterns, behavioural responses to fatigue symptoms), N = 205 adolescents (age 11 to 18) with confirmed CFS/ME.


Study 1: One third of the participants met the diagnostic criteria for current depression and/or anxiety. Of these, approximately 20% met the criteria for a major depressive disorder, and 27% an anxiety disorder, with many meeting the criteria for more than one disorder concurrently. The questionnaires I tested were not sufficiently accurate for screening purposes, apart from the Revised Children’s Anxiety and Depression Scale-anxiety subscale (self-report and parent versions).
Study 2: Co-morbid depression and/or anxiety symptoms were common (45.3%) and at baseline, the odds of having co-morbid depression and/or anxiety symptoms increased 1.18- fold (95% CI 1.10, 1.26, p<0.001) for every one-point increase in baseline fatigue severity. Those with higher depression and/or anxiety symptom scores at baseline had worse fatigue severity, physical functioning, and school attendance 6 months later.
Study 3: Participants who had co-morbid depression and/or anxiety symptoms more strongly endorsed all the general negative thinking patterns than those with CFS/ME only. They also more strongly endorsed most types of unhelpful cognitive responses to fatigue, specifically damage beliefs, embarrassment avoidance, catastrophising and symptom focusing. Fear avoidance beliefs were strongly endorsed by both groups, irrespective of their co-morbid mental health status. Participants with co-morbid depression and/or anxiety symptoms also endorsed more strongly both all-or-nothing behaviours and avoidance/resting behaviours.


A substantial minority of adolescents with CFS/ME are likely to have co-morbid depression and/or anxiety, particularly those who are more fatigued and more impaired. They also continue to be more impaired and fatigued at follow-up. In terms of potential treatment targets, those with comorbid depression and/or anxiety tend to endorse more negative general and fatigue-specific thinking patterns. Treatments need to be adapted for this subgroup. My programme of work culminated in using the existing evidence and public and patient involvement from healthcare professionals and young people with lived experience of CFS/ME to describe a potential adapted treatment approach based on co-produced logic models. This approach will need to be evaluated in future and my work has laid the foundations for a clinical trial, although more work is needed.
Date of Award22 Mar 2022
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorEsther M Crawley (Supervisor), David S Kessler (Supervisor) & Paul Stallard (Supervisor)

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