Severe health anxiety : novel approaches to diagnosis and psychological treatment

University dissertation from Stockholm : Karolinska Institutet, Dept of Clinical Neuroscience

Abstract: Background: It has long been known that severe health anxiety is a common psychiatric condition associated with significant distress, functional impairment, and societal costs. Nevertheless, challenges remain with regard to the diagnosis and treatment of this disorder. As to diagnostic assessment, a recent shift in diagnostic taxonomy for individuals with severe health anxiety has led to a need for reliable instruments to aid clinicians and researchers in assessing the new diagnoses somatic symptom disorder (SSD) and illness anxiety disorder (IAD). As to treatment, individual face-to-face cognitive behaviour therapy (FTF-CBT) is the most researched and widely recommended treatment for severe health anxiety, but the availability of FTF-CBT is poor. Therapist-guided internet cognitive behaviour therapy (G-ICBT) may improve the scalability of evidence-based treatment, but it is unclear if this treatment could be efficacious and cost-effective also if delivered without a therapist or as book-form bibliotherapy. It is also unclear if the effect of G-ICBT is non-inferior to that of FTF-CBT. Aims: To develop, and evaluate the inter-rater reliability of, a structured diagnostic interview for the assessment of SSD and IAD (Study I). Also, to evaluate the efficacy of three forms of minimal-contact cognitive behaviour therapy for severe health anxiety (Study II) and to investigate their long-term efficacy and cost-effectiveness (Study III). Last, to determine if G- ICBT is non-inferior to FTF-CBT in the treatment of severe health anxiety (Study IV). Methods: The inter-rater reliability of a new structured diagnostic interview for SSD and IAD was estimated based on concordance between the ratings of an interviewer and an independent clinician who listened to recorded interviews (Study I). The effects of different forms of minimal-contact cognitive behaviour therapy for severe health anxiety were also studied in two randomised controlled trials (RCTs). The first RCT (N=132) compared G- ICBT, unguided internet cognitive behaviour therapy (U-ICBT), and cognitive behavioural bibliotherapy (BIB-CBT) to a waiting-list control (WLC) condition. Primary outcome was short-term change in health anxiety, as measured with the 64-item Health Anxiety Inventory (Study II). Among the secondary outcomes of this trial were long-term symptom levels up to 1 year after treatment, and cost-effectiveness as based on the incremental cost-effectiveness ratio (ICER) vs. the WLC (Study III). The second RCT (N=204) compared G-ICBT to FTF- CBT based on a non-inferiority criterion of 2.25 points on the 18-item Short Health Anxiety Inventory (d=0.3), as assessed over the 12-week treatment period (Study IV). Results: The inter-rater reliability of diagnostic decisions regarding SSD and IAD based on the new structured instrument – the Health Preoccupation Diagnostic Interview (HPDI) – was moderate (κ=.59) for clinical trial applicants, perfect (κ not applicable) for healthy controls, and almost perfect (κ=.85) for the pooled sample (Study I). G-ICBT, U-ICBT, and BIB-CBT all produced large waiting-list controlled reductions (d=0.80–1.27) in health anxiety (Study II). These effects were then sustained one year after treatment, and cost-effectiveness was high (waiting-list controlled ICERs=£ -134–416) for all three treatment formats (Study III). In the comparison of G-ICBT to FTF-CBT, the upper limit of the one-sided 95% confidence interval for the difference in change over the 12-week treatment period was 1.98 based on intention-to-treat data, and 2.17 based on per-protocol data. Both estimates were below the non-inferiority margin of 2.25 points, indicating that G-ICBT is not inferior to FTF-CBT in the treatment of severe health anxiety (Study IV). Conclusions: As hypothesised, the inter-rater reliability of SSD and IAD can be satisfactory if diagnoses are based on the HPDI, though the psychometric properties of this instrument need be studied further (Study I). G-ICBT, U-ICBT, and BIB-CBT are efficacious and cost- effective treatments for severe health anxiety, with the potential to greatly increase treatment availability, not least in the primary and medical care context (Studies II and III). Because G- ICBT is not inferior to FTF-CBT (Study IV), G-ICBT may be regarded as a first-line treatment for severe health anxiety, which calls for further implementation of this treatment format in routine care.

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