Microbiome in Obsessive-compulsive Disorder
Condition: Obsessive-Compulsive Disorder; Microbiota
MeSH terms: Compulsive Personality Disorder; Obsessive-Compulsive Disorder
Study type: Observational [Patient Registry]

Summary: 
      Background: Humans live in symbiosis with microbes and their implication for health and
      disease is evident. The importance of microbiome-gut-brain axis in psychiatric disorders is
      an area of increasing research interest. OCD is a promising target for microbiome research as
      Pediatric Acute-onset Neuropsychiatric Syndrome (PANS)/ Pediatric autoimmune neuropsychiatric
      disorders associated with streptococcal infections (PANDAS) are reactions to infectious
      agents precipitating acute onset of severe OCD symptoms. Furthermore, preliminary evidence
      has associated probiotic treatment with alleviation of OCD symptoms. We propose the first
      clinical study on the microbiome and its effects on OCD patients.

      Aim: To analyze the gut microbiota in patients with OCD compared with healthy matched
      controls and assess changes in microbial composition following treatment.

      Outcome measures: Differences in alpha diversity, beta diversity, and taxa abundance of
      bacterial groups (at the phylum, class, order, family, genus and species levels) and severity
      of OCD symptoms. Moreover, functional profiling will be conducted.

      Methods: Our aim is to enroll 32 OCD patients and 32 matched controls. Shotgun metagenomic
      sequencing will be used. Sequenced data will be processed followed by non-parametric
      statistical testing.

      Significance: gut microbiome in patients with OCD beofre and after ERP treatment has never
      been done before. The microbial composition may impact on OCD symptoms, severity, and
      chronicity and could inform future therapeutic possibilities.
    

Detailed description: 
      Background:

      Obsessive-compulsive disorder (OCD) is a highly debilitating disorder with a lifetime
      prevalence of approximately 2% is equally distributed among men and women. OCD generally
      starts at an early age and usually develops a chronic course if left untreated. Many patients
      with OCD receive treatment after years of delay due to both patient and health care factors;
      therefore, OCD affects educational achievement, ability to work and interpersonal
      relationships. Moreover, it poses a considerable burden and distress to family caregivers
      [1], and accounts for one of the ten most disabling mental health conditions worldwide [2].

      The role of the microbial community in health and disease has been a neglected subject in
      human research until recently, despite the fact that human microbes comprise about 1-3 % of
      our body mass [3]. Gut microbes play important roles in nutrient metabolism, production of
      vitamins, and prevention of pathogens from colonizing our intestine [4]. Recently, microbiota
      in the gut has gained increasing interest due the extensive connection between the gut and
      the brain [5]. The bidirectional communication through neural, hormonal, and immunological
      signaling involving the central, autonomic, and enteric nervous systems forms the
      microbiome-gut-brain axis [6]. In psychiatry, dysbioses have been reported in anorexia
      nervosa, major depression, autism, and other major psychiatric disorders [9, 10].

      Association between OCD onset and infection has long been known. PANS/PANDAS are acute-onset
      forms of OCD associated with autoimmune reactions from pathogens such as streptococcus
      infection [11, 12]. The connection between bacterial pathogen and immunological response,
      which generates OCD symptoms, is further evidence for the importance of the
      microbiome-gut-brain axis in OCD. Lately, there have been numerous hypotheses regarding the
      importance of gut microbiome and OCD symptoms [13, 14].

      Aims: Characterize composition and diversity of the gut microbiome in individuals with OCD
      compared with healthy controls.

        -  We hypothesize that patients with OCD will show evidence of gut dysbiosis (imbalance)
           marked by lower microbial diversity and specific taxonomic and gene content differences
           compared to healthy controls. Primary outcome is α-diversity, which refers to the number
           of species (richness) at one site, β-diversity, which refers to the differences in
           species composition between participants, and taxonomic abundance of bacterial groups
           (at the phylum, class, order, family, genus, and species levels). These measures yield
           information about individual microbial composition at each site and homogeneity in a
           group of people.

        -  We hypothesize that reduced α and β diversity in gut microbiome correlate with severity
           of obsessive-compulsive symptoms measured by Yale-Brown Obsessive-Compulsive Scale
           (Y-BOCS), and Obsessive-Compulsive Inventory Revised (OCI-R). We predict that greater
           symptom severity is associated with lower diversity. A significant negative correlation
           will be supportive evidence for the microbiome-gut-brain axis.

        -  We hypothesize that there will be significant richer α diversity in gut microbiome
           composition after successful psychotherapy (change in Y-BOCS score).

      Method:

      Recruitment: Healthy controls will be recruited through advertisement or included from
      previous studies with their consent. Male and female patients between 18-45 years of age from
      the OCD-clinic at Huddinge Hospital with a DSM-5 diagnosis of OCD and fear of contamination
      will be invited to participate. Age matched controls will be recruited who have no personal
      or family history of OCD. Exclusion criteria for all groups include history of GI tract
      surgery (other than appendectomy or cholecystectomy); history of inflammatory bowel disease,
      irritable bowel syndrome, celiac disease, or any other diagnosis that could explain chronic
      or recurring bowel symptoms, antibiotic use in the past 3 months; pro-biotic use in the past
      4 weeks; pregnantcy. Intellectual disability, autism spectrum disorder and psychosis.

      Assessment: All participants will meet an experienced psychiatrist for diagnostic assessments
      including M.I.N.I. interview. Participants will be asked to complete self-assessment forms on
      the Internet and answer questions about their dietary habits for the last three months.
      Weight and height for body mass index (BMI) calculation will be measured. All assessment
      forms, information from interviews and medical examination will be documented in their
      medical record. Further information (e.g. antibiotics and previous therapies) will be
      collected from their medical records with the participants' consent.

      The investigators chose the following questionnaire battery to capture all relevant outcome
      variables (OCD-symptoms), nutrition, and stool characteristics and frequency.

        -  Yale-Brown Obsessive Compulsive Scale (Y-BOCS): A commonly used clinical,
           semi-structured interview assessing severity of OCD symptoms.

        -  Obsessive-Compulsive Inventory Revised (OCI-R -): An18 item self-report questionnaire
           estimating OCD symptom dimensions.The OCI-R yields a total score and 5 subscales:
           checking, hoarding, neutralizing, obsessing, ordering and washing.

        -  EDE-Q to capture eating behavior.

        -  Meal Q questionnaire: A web-based food frequency questionnaire normed in Sweden will
           validate energy and macronutrient intake, which affects the microbial composition.

        -  Bristol Stool Scale: A medical diagnostic scale designed to classify the form of human
           faeces into seven categories.

      Furthermore, the investigators will collect demographic information of all patients: age,
      sex, age at onset, occupation status, somatic health, and psychiatric comorbidities.

      Stool sampling procedure: Patients and controls will be provided with clear instructions for
      home fecal sample collection. Patients will collect one stool sample at the beginning of
      treatment and one at the end of treatment. Controls will collect one sample at one time point
      only. Participants will collect stool at home using OMNIgene kits that will be sent to the KI
      biobank.

      Exposure and Respons Prevention therapy (ERP): an evidence-based psychotherapy administered
      by experienced psychologists, either individually, in groups, face-to-face or through
      internet. A minimum of five exposure and respons prevention sessions is required in order for
      it to be considered an ERP treatment.

      Sample storage in biobank: All samples will be stored at Karolinska Institutets (KI) biobank.
      Application for biobank storage of samples is established according to rules and regulations.

      Metagenomic sequencing: The investigators will use shotgun metagenomics sequencing methods.
      Whole-genome shotgun sequencing can provide functional information on which genes are present
      in the gut microbiome of patients. This method can also provide a more detailed taxonomical
      resolution that 16S rRNA sequencing.

      Metagenomic shotgun sequencing: will be prepared and sequenced. To efficiently utilize the
      flow cells, about ten samples will be multiplexed, with dual indices, per lane of the flow
      cell. Prior to downstream bioinformatics analysis, raw sequence data will be quality filtered
      and trimmed to remove bases with Phred quality scores less than 20. Data generated will be
      processed by metagenome species concept. Sequences are clustered into metagenomic species
      (MGS) based on their sequence similarity.

      Determination of sample size: two previous studies with fewer or similar number of
      participants have shown that this study will be adequately powered. Furthermore, this is a
      pilot study based on new sequencing technology.

      Timeline: Ethical application has been approved and all samples have been collected.
    

Intervention name(s): Exposure and response inhibition
Intervention type(s): Behavioral
Intervention description(s): Cognitive behavioural therapy designed for treatment of Obsessive-compulsive disorder
Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Recruitment of participants from Karolinska Hospital in Solna and Huddinge. Healthy
        Controls are recruited from Sweden from advertisements.
      
Biospecimen description: 
      Stool samples