The aim of this study is to evaluate the clinical effectiveness of internet-based cognitive therapy for severe health anxiety within regular psychiatric care.

A longitudinal cohort study will be conducted investigating 400 patients who have received ICBT for severe health anxiety between 2018-2020 in an outpatient psychiatric clinic providing Internet-based treatment.

The primary outcome measure will be the Short Health Anxiety Inventory, SHAI, and a within-group design with repeated measures will be used for primary analysis.

It is hypothesized that ICBT will be associated with a significant reduction in health anxiety as measured with SHAI, both after treatment and at six-month follow-up.

Severe health anxiety is a prevalent disorder, leading to considerable distress and is associated with high societal costs. Internet-based cognitive behaviour therapy is a method to improve access to evidence-based psychological treatments and it has shown to be efficacious in the treatment of severe health anxiety in several randomized controlled trials. However, there is limited knowledge of its effectiveness and application in clinical psychiatric care.

The aim of this study is to evaluate the clinical effectiveness of internet-based cognitive therapy for severe health anxiety within regular psychiatric care.

The investigators will conduct at a cohort-study with a pretest-posttest design investigating consecutively recruited patients from May 2018 to April 2021 in an outpatient psychiatric clinic specialised in delivering ICBT. The treatment content has been successfully tested in previous efficacy studies and will be delivered during 13 weeks. The primary outcome measure will be the gold standard SHAI and a within-group design with repeated measures will be used in the primary analysis. It is estimated that 400 patients will receive treatment during this period and thus be included in the study, if consenting.

It is hypothesized that ICBT will be associated with a significant reduction in health anxiety as measured with SHAI, both after treatment and at six-month follow-up. The effect size is expected to be somewhat smaller than in research trials but still moderate to large (d > 0.5).

Inclusion Criteria:

• Patients over 16 years of age
• Living in Sweden
• Primary diagnosis of hypochondriasis according to ICD-10
• Able to read and write
• Have access to a computer or other device with an Internet connection
• If on medication, have a stable dose of psychotropic medication for 4 weeks prior to treatment
• Not having other psychiatric difficulties (e.g., ongoing substance abuse or a psychotic syndrome) that makes ICBT an unsuitable intervention

Exclusion Criteria:

• Patients with severe depression (clinician rated Montgomery-Asberg Depression Rating Scale- Self-Rated; MADRS-S and/or moderate to high risk of suicide in which monitoring is required
• Patients with low motivation, severe apathy, or difficulty concentrating
• Patients with psychosis
• Patients with untreated drug or alcohol problems
• Patients with reading and/or writing difficulties, including language difficulties;

All patients will receive treatment at the Internet Psychiatry Clinic (www.internetpsykiatri.se), Psychiatry Southwest, Karolinska University Hospital Huddinge. Patient can either apply for treatment through self-referral or through referral from primary or psychiatric care. Self-referred patients will register for treatment through a public e-service portal for health care (i.e.Vårdguiden; 1177.se).

Prior to treatment, patients will complete an online screening battery of self-report questionnaires and undergo an assessment by psychiatrists, or resident physicians supervised by psychiatrists.