Internet Supported Group Cognitive Behavior Therapy (CBT) for Hoarding Disorder (HD)

The primary aim is to develop, and test the feasibility and efficacy of, a manual based, cognitive behaviour therapy (CBT) treatment for Hoarding Disorder (HD) delivered in a group format combined with an Internet support system. The investigators' secondary aim is to investigate the neurocognitive profile of the participants before and after treatment in order to explore if the treatment might have an impact on neurocognitive functioning and if certain neurocognitive profiles predict outcome. For the primary aim, the investigators hypothesize that the treatment will be acceptable to participants and decrease symptoms of hoarding. Regarding the secondary aim, the investigators hypothesize that deficiencies in executive functioning, as measured with a neurocognitive battery, will reduce upon completion of treatment and that baseline executive function will be associated with treatment outcome.

The SI-R is a 23-item self-report questionnaire. It assesses hoarding symptoms in 3 sub-scales: difficulty discarding, clutter and excessive acquisition.

The questionnaire is a 24-item self-report questionnaire assessing beliefs and attitudes participants experience when trying to discard items. It is divided in 4 subscales:emotional attachment to objects, beliefs about objects as memory aids, responsibility for not wasting possessions, and the need for control over possessions.

This scale consists of three sets of photographs each containing nine photos of a single room with varying levels of clutter. Study participants will select the photograph that best resembles his or her own home. The study investigators will also conduct blinded ratings of the same photos.

A scale used to rate the social, occupational, and psychological functioning of the study participants.

A 7 point scale to rate how much the patient's illness has improved or worsened relative to a baseline state at the beginning of the intervention.

In this questionnaire, study participants register their monthly health care consumption (e.g. GP visits) as well as time spent in informal health enhancing activities (e.g. self-help groups and informal care from friends). Additionally, work loss and work cutback both at work and in the domestic realm is measured.

Presence of Hoarding Disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Assessed by the investigators using the Structured Interview for Hoarding Disorder.

Presence of psychiatric diagnoses other than Hoarding Disorder. Assessed by the investigators using the M.I.N.I. International Neuropsychiatric Interview (M.I.N.I. 6.0).

Cambridge Automated Neuropsychological Test Battery (CANTAB) will be used to test the study participants in 3 aspects of executive function: shifting and flexibility of attention, visuospatial working memory and response inhibition

Inclusion criteria: Outpatients Male or female ≥ 18 years of age Currently living in Stockholm county Primary diagnosis of Hoarding Disorder according to DSM-5 Signed informed consent Regular access to a computer with Internet and ability to use Internet Access to a mobile phone Able to participate in group sessions Exclusion criteria: Current substance dependence or misuse Life time bipolar disorder or psychosis Severe self-rated depressive symptoms (score ≥ 35 on MADRS-S) Suicidal ideation (score > 4 on item 9 in MADRS-S) Psychotropic medication changes within two months prior to the treatment Other current psychological treatment that could affect hoarding symptoms Has received more than 10 CBT sessions for Hoarding Disorder