Never let go! : the etiology, clinical presentation and treatment of hoarding disorder

Sammanfattning: Background: Hoarding disorder (HD) is characterized by difficulties discarding possessions which results in clutter that is impeding and causes distress. Retrospective reports suggest HD debuts in childhood or adolescence but very little is known about the prevalence, presentation and etiology of hoarding in young people. Furthermore, although cognitive behavior therapy (CBT) for HD reduces hoarding symptoms, treatment engagement is generally low and many individuals with HD remain symptomatic after CBT. Aims: The general aims of this thesis were to examine the prevalence, etiology and clinical presentation of hoarding symptoms in young people and to develop and test a novel treatment for adults with HD. Results: In study I we analyzed data from a sample (n=3,974) of 15-year old twins from the Swedish Twin Registry and estimated the prevalence of clinically significant hoarding symptoms. Using twin methods, we also estimated the genetic and environmental effects on hoarding symptoms. We found that clinically significant hoarding symptoms occurred in 2.0% of the sample. In boys, the heritability was estimated to 32% and in girls to 2%. Non-shared environmental effects accounted for the remaining variance in boys. In girls, shared environmental effects accounted for 32% and non-shared environmental effects for the remaining variance. In study II, we estimated the heritability of hoarding symptoms in three cohorts of twins aged 15 (n=7,905), 18 (n=2,495) and 20-28 (n=6,218). We also estimated the sources of stability and change of hoarding symptoms in a sample with available data at ages 15 and 18 (n=1,701). Heritability for hoarding symptoms at ages 15, 18 and 20-28 ranged from 41% (age 15) to 29% (age 20-28). Shared environmental effects were significant only in girls at age 15 and accounted for 22% of the variance at that age. Longitudinal bivariate analyses revealed a significant phenotypic correlation of hoarding symptoms between ages 15 and 18, and a genetic correlation. The bivariate heritability was estimated to 65%. In study III, we conducted follow-up assessments of twins who screened positive for clinically significant hoarding symptoms 1-6 years after the survey in study I. None of the participants met full diagnostic criteria for HD. Twins who met diagnostic criteria A and B for HD, were compared to a group of twins who did not meet these criteria. Twins in the hoarding group were more psychiatrically burdened and the clinical presentation was similar to the presentation in adults with HD. In study IV, we developed and tested a novel treatment for adults with HD which consisted of group CBT and online between-session therapist support. Twenty self- and clinically referred adults were treated. After treatment, we observed large reductions in hoarding symptoms. Treatment engagement and treatment acceptance were high and none of the participants dropped out from treatment. The treatment gains were maintained three months after treatment was completed. Conclusions: Hoarding symptoms are common during adolescence and young adulthood and may cause distress and impairment. However, none of the participants that were followed up in clinical assessments met diagnostic criteria for HD. Hoarding symptoms are heritable in young people but non-shared environmental factors appear to have a larger effect. Group CBT combined with online between session therapist support is a feasible and efficacious treatment for adults with HD and might increase treatment adherence.