The treatment primarily targets the dysfunctional reasoning that gives rise to obsessional doubts and overvalued ideas. IBCT does not include exposure in vivo, but instead, aims to bring resolution to the initial obsessional doubt or overvalued idea by showing the participant that the obsession is the result of incorrect reasoning.

The Yale-Brown Obsessive Compulsive Scale (Y-BOCS) is a 10-item scale designed to measure the severity and type of symptoms in people with obsessive-compulsive disorder (OCD) over the past seven days. The symptoms assessed are obsessions and compulsions. This scale is useful in tracking OCD symptoms at intake and during/after treatment.

Total Y-BOCS scores range from 0 to 40, with higher scores indicating greater severity of OCD symptoms. Scores on the obsession and compulsion subscales range from 0 to 20, but only the total Y-BOCS score is interpreted. Total scores can be split into five categories, based on severity of symptoms. People who have a total Y-BOCS score:

Under 7 are likely to be subclinical, 8-15 are likely to have a mild case of OCD, 16-23 are likely to have a moderate case of OCD, 24-31 are likely to have a severe case of OCD, 32-40 are likely to have an extreme case of OCD.

The Over-Valued Ideas Scale (OVIS) is an 11-item clinician administered scale assess severity of overvalued ideation. These include how strong obsessive belief; how reasonable the belief is; how weak and strong the belief has fluctuated over the past week; how accurate the belief is; the extent to which others share the same beliefs; how the patient attributes similar or differing beliefs in other people; how effective and important the compulsions are; the extent to which their disorder has caused their obsessive belief; and their degree of resistance toward the belief on a 1 to 10 scale. The average of the 11 items provides an estimate of one's degree of OVI, where higher scores represent greater levels of OVI.

The Over-Valued Ideas Scale (OVIS) is an 11-item clinician administered scale assess severity of overvalued ideation. These include how strong obsessive belief; how reasonable the belief is; how weak and strong the belief has fluctuated over the past week; how accurate the belief is; the extent to which others share the same beliefs; how the patient attributes similar or differing beliefs in other people; how effective and important the compulsions are; the extent to which their disorder has caused their obsessive belief; and their degree of resistance toward the belief on a 1 to 10 scale. The average of the 11 items provides an estimate of one's degree of OVI, where higher scores represent greater levels of OVI.

The Over-Valued Ideas Scale (OVIS) is an 11-item clinician administered scale assess severity of overvalued ideation. These include how strong obsessive belief; how reasonable the belief is; how weak and strong the belief has fluctuated over the past week; how accurate the belief is; the extent to which others share the same beliefs; how the patient attributes similar or differing beliefs in other people; how effective and important the compulsions are; the extent to which their disorder has caused their obsessive belief; and their degree of resistance toward the belief on a 1 to 10 scale. The average of the 11 items provides an estimate of one's degree of OVI, where higher scores represent greater levels of OVI.

The Over-Valued Ideas Scale (OVIS) is an 11-item clinician administered scale assess severity of overvalued ideation. These include how strong obsessive belief; how reasonable the belief is; how weak and strong the belief has fluctuated over the past week; how accurate the belief is; the extent to which others share the same beliefs; how the patient attributes similar or differing beliefs in other people; how effective and important the compulsions are; the extent to which their disorder has caused their obsessive belief; and their degree of resistance toward the belief on a 1 to 10 scale. The average of the 11 items provides an estimate of one's degree of OVI, where higher scores represent greater levels of OVI.

The Vancouver Obsessional-Compulsive Inventory (VOCI) is a 55-item self-report measure designed to assess a broad spectrum of OCD symptoms and associated personality characteristics. Items are rated on a 5-point Likert scale, ranging from 0 (not at all) to 4 (very much), and measure participants' agreement with a series of statements related to obsessions and compulsions (e.g., ''I am often very upset by my unwanted impulses to harm other people''). The VOCI has six component subscales: (a) Checking; (b) Contamination; (c) Obsessions; (d) Hoarding; (e) ''Just Right''; and (f) Indecisiveness.

The Vancouver Obsessional-Compulsive Inventory (VOCI) is a 55-item self-report measure designed to assess a broad spectrum of OCD symptoms and associated personality characteristics. Items are rated on a 5-point Likert scale, ranging from 0 (not at all) to 4 (very much), and measure participants' agreement with a series of statements related to obsessions and compulsions (e.g., ''I am often very upset by my unwanted impulses to harm other people''). The VOCI has six component subscales: (a) Checking; (b) Contamination; (c) Obsessions; (d) Hoarding; (e) ''Just Right''; and (f) Indecisiveness.

The Vancouver Obsessional-Compulsive Inventory (VOCI) is a 55-item self-report measure designed to assess a broad spectrum of OCD symptoms and associated personality characteristics. Items are rated on a 5-point Likert scale, ranging from 0 (not at all) to 4 (very much), and measure participants' agreement with a series of statements related to obsessions and compulsions (e.g., ''I am often very upset by my unwanted impulses to harm other people''). The VOCI has six component subscales: (a) Checking; (b) Contamination; (c) Obsessions; (d) Hoarding; (e) ''Just Right''; and (f) Indecisiveness.

The Beck Depression Inventory, version II consists of 21 items assessing symptoms of depression experienced during the past 2 weeks. Each item contains four statements reflecting varying degrees of symptom severity. Respondents are instructed to circle the number (ranging from zero to three, indicating increasing severity) that corresponds with the statement that best describes them. Ratings are summed to calculate a total Beck Depression Inventory, version II score, which can range from 0 to 63.

The Beck Depression Inventory, version II consists of 21 items assessing symptoms of depression experienced during the past 2 weeks. Each item contains four statements reflecting varying degrees of symptom severity. Respondents are instructed to circle the number (ranging from zero to three, indicating increasing severity) that corresponds with the statement that best describes them. Ratings are summed to calculate a total Beck Depression Inventory, version II score, which can range from 0 to 63.

The Beck Depression Inventory, version II consists of 21 items assessing symptoms of depression experienced during the past 2 weeks. Each item contains four statements reflecting varying degrees of symptom severity. Respondents are instructed to circle the number (ranging from zero to three, indicating increasing severity) that corresponds with the statement that best describes them. Ratings are summed to calculate a total Beck Depression Inventory, version II score, which can range from 0 to 63.

The Beck Depression Inventory, version II consists of 21 items assessing symptoms of depression experienced during the past 2 weeks. Each item contains four statements reflecting varying degrees of symptom severity. Respondents are instructed to circle the number (ranging from zero to three, indicating increasing severity) that corresponds with the statement that best describes them. Ratings are summed to calculate a total Beck Depression Inventory, version II score, which can range from 0 to 63.

The Beck Depression Inventory, version II consists of 21 items assessing symptoms of depression experienced during the past 2 weeks. Each item contains four statements reflecting varying degrees of symptom severity. Respondents are instructed to circle the number (ranging from zero to three, indicating increasing severity) that corresponds with the statement that best describes them. Ratings are summed to calculate a total Beck Depression Inventory, version II score, which can range from 0 to 63.

The Beck Anxiety inventory is a scale of 21 items describe the most typical symptoms of anxiety disorders. It was developed to measure the intensity of anxiety symptoms in clinical populations. It asks respondents to indicate how much they have been affected by each symptom during the last week, on a scale from 0 (Not at all) to 3 (Severely - I could barely stand it). Total scores are the sum of all item scores, and range from 0 to 63; higher scores indicate higher anxiety.

The Beck Anxiety inventory is a scale of 21 items describe the most typical symptoms of anxiety disorders. It was developed to measure the intensity of anxiety symptoms in clinical populations. It asks respondents to indicate how much they have been affected by each symptom during the last week, on a scale from 0 (Not at all) to 3 (Severely - I could barely stand it). Total scores are the sum of all item scores, and range from 0 to 63; higher scores indicate higher anxiety.

The Beck Anxiety inventory is a scale of 21 items describe the most typical symptoms of anxiety disorders. It was developed to measure the intensity of anxiety symptoms in clinical populations. It asks respondents to indicate how much they have been affected by each symptom during the last week, on a scale from 0 (Not at all) to 3 (Severely - I could barely stand it). Total scores are the sum of all item scores, and range from 0 to 63; higher scores indicate higher anxiety.

The Beck Anxiety inventory is a scale of 21 items describe the most typical symptoms of anxiety disorders. It was developed to measure the intensity of anxiety symptoms in clinical populations. It asks respondents to indicate how much they have been affected by each symptom during the last week, on a scale from 0 (Not at all) to 3 (Severely - I could barely stand it). Total scores are the sum of all item scores, and range from 0 to 63; higher scores indicate higher anxiety.

The Sheehan Disability Scale is a standard measure of impairment in work, social life and family responsibilities which was a composite of 3 self-rated 10-point (0=none, l-3=mild, 4-6=moderate, 7-9=marked, and 10=extreme) Likert response items to assess work, family, and social functioning during the last month.

The Sheehan Disability Scale is a standard measure of impairment in work, social life and family responsibilities which was a composite of 3 self-rated 10-point (0=none, l-3=mild, 4-6=moderate, 7-9=marked, and 10=extreme) Likert response items to assess work, family, and social functioning during the last month.

The Sheehan Disability Scale is a standard measure of impairment in work, social life and family responsibilities which was a composite of 3 self-rated 10-point (0=none, l-3=mild, 4-6=moderate, 7-9=marked, and 10=extreme) Likert response items to assess work, family, and social functioning during the last month.

EuroQol-5dimensions is a standardized instrument developed by the EuroQol Group as a measure of health-related quality of life that can be used in a wide range of health conditions and treatments. The EQ-5Dimensions consists of a descriptive system and the EQ Value Average Score.

The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EQ Value Average Score used as a quantitative measure of health outcome that reflects the participant's own judgement. The scores on these five dimensions can be presented as a health profile or can be converted to a single summary index number (utility) reflecting preferability compared to other health profiles.

The final score is a scale numbered from 0 to 100, where100 means the best health you can imagine and 0 means the worst health you can imagine.

EuroQol-5dimensions is a standardized instrument developed by the EuroQol Group as a measure of health-related quality of life that can be used in a wide range of health conditions and treatments. The EQ-5Dimensions consists of a descriptive system and the EQ Value Average Score.

The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EQ Value Average Score records the participant's self-rated health on a vertical visual analogue scale. This can be used as a quantitative measure of health outcome that reflects the participant's own judgement. The scores on these five dimensions can be presented as a health profile or can be converted to a single summary index number (utility) reflecting preferability compared to other health profiles.

The final score is a scale numbered from 0 to 100, where100 means the best health you can imagine and 0 means the worst health you can imagine.

EuroQol-5dimensions is a standardized instrument developed by the EuroQol Group as a measure of health-related quality of life that can be used in a wide range of health conditions and treatments. The EQ-5Dimensions consists of a descriptive system and the EQ Value Average Score.

The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. The EuroQuol Value Average Score records the participant's self-rated health on a vertical visual analogue scale. This can be used as a quantitative measure of health outcome that reflects the participant's own judgement. The scores on these five dimensions can be presented as a health profile or can be converted to a single summary index number (utility) reflecting preferability compared to other health profiles.

The final score is a scale numbered from 0 to 100, where100 means the best health you can imagine and 0 means the worst health you can imagine.

The Inferential Confusion Questionnaire-Expanded Version (ICQ-EV) is a 30-item questionnaire measuring an overreliance on imagination, a distrust of the senses, and a tendency to confuse imagination with reality during reasoning. Like the original version, the expanded version of the ICQ is a highly reliable measure that has been shown to explain a large portion of the variance in symptoms of OCD independent of negative mood states and other cognitive domains. Items are rated on a 6-point scale .

The Inferential Confusion Questionnaire-Expanded Version (ICQ-EV) is a 30-item questionnaire measuring an overreliance on imagination, a distrust of the senses, and a tendency to confuse imagination with reality during reasoning. Like the original version, the expanded version of the ICQ is a highly reliable measure that has been shown to explain a large portion of the variance in symptoms of OCD independent of negative mood states and other cognitive domains. Items are rated on a 6-point scale .

The Inferential Confusion Questionnaire-Expanded Version (ICQ-EV) is a 30-item questionnaire measuring an overreliance on imagination, a distrust of the senses, and a tendency to confuse imagination with reality during reasoning. Like the original version, the expanded version of the ICQ is a highly reliable measure that has been shown to explain a large portion of the variance in symptoms of OCD independent of negative mood states and other cognitive domains. Items are rated on a 6-point scale .

The obsessive beliefs questionnaire is a 20-item key self report questionnaire measuring change in obsessive beliefs domains. Items are answered on a 7-point Likert-type scale (disagree very much to agree very much) in relation to "what you are like most of the time."

The obsessive beliefs questionnaire is a 20-item key self report questionnaire measuring change in obsessive beliefs domains. Items are answered on a 7-point Likert-type scale (disagree very much to agree very much) in relation to "what you are like most of the time."

The obsessive beliefs questionnaire is a 20-item key self report questionnaire measuring change in obsessive beliefs domains. Items are answered on a 7-point Likert-type scale (disagree very much to agree very much) in relation to "what you are like most of the time."

The Treatment Acceptability/Adherence Scale (TAAS) will be tested by comparing our indices of tolerability across the two treatments. It is a 10-item scale rated on a 7-point scale and assesses acceptability of and anticipated adherence to a given treatment. Higher scores represent greater acceptability.

The Treatment Acceptability/Adherence Scale (TAAS) will be tested by comparing our indices of tolerability across the two treatments. It is a 10-item scale rated on a 7-point scale and assesses acceptability of and anticipated adherence to a given treatment. Higher scores represent greater acceptability.

The Treatment Acceptability/Adherence Scale (TAAS) will be tested by comparing our indices of tolerability across the two treatments. It is a 10-item scale rated on a 7-point scale and assesses acceptability of and anticipated adherence to a given treatment. Higher scores represent greater acceptability.

The Credibility and Expectancy Questionnaire (CEQ) is a 6-item measure divided into two subscales assessing treatment credibility (CEQ-Credibility) and expectancy (CEQ-Expectancy), respectively. The first three CEQ items assess credibility and are rated from 1 to 9 with total possible scores ranging from 3 to 27, where higher scores indicate greater credibility beliefs. The final three CEQ items assess expectancy, with one item rated from 1 to 9, and two items rated from 0% to 100% (values from 1 to 11). We standardized these three items into z scores before summing to create the total Expectancy score. The Expectancy scale scores ranged from -6.72 to 5.51, where higher scores indicate higher expectations.

The Credibility and Expectancy Questionnaire (CEQ) is a 6-item measure divided into two subscales assessing treatment credibility (CEQ-Credibility) and expectancy (CEQ-Expectancy), respectively. The first three CEQ items assess credibility and are rated from 1 to 9 with total possible scores ranging from 3 to 27, where higher scores indicate greater credibility beliefs. The final three CEQ items assess expectancy, with one item rated from 1 to 9, and two items rated from 0% to 100% (values from 1 to 11). We standardized these three items into z scores before summing to create the total Expectancy score. The Expectancy scale scores ranged from -6.72 to 5.51, where higher scores indicate higher expectations.

The Credibility and Expectancy Questionnaire (CEQ) is a 6-item measure divided into two subscales assessing treatment credibility (CEQ-Credibility) and expectancy (CEQ-Expectancy), respectively. The first three CEQ items assess credibility and are rated from 1 to 9 with total possible scores ranging from 3 to 27, where higher scores indicate greater credibility beliefs. The final three CEQ items assess expectancy, with one item rated from 1 to 9, and two items rated from 0% to 100% (values from 1 to 11). We standardized these three items into z scores before summing to create the total Expectancy score. The Expectancy scale scores ranged from -6.72 to 5.51, where higher scores indicate higher expectations.

The Evaluation of Treatment Questionnaire is a 19-item subjective measure assessing treatment satisfaction. It is a qualitative and quantitative questionnaire. The first two items assess how far therapy help, their importance and the satisfaction. The second part rate what the participant think about the therapy in a 1 to 10 scale. The third part assess what participant feel about the therapy on different scale. Finally, the last part rate satisfaction, preoccupation, stress and what the less like about the therapy.

The Evaluation of Treatment Questionnaire is a 19-item subjective measure assessing treatment satisfaction. It is a qualitative and quantitative questionnaire. The first two items assess how far therapy help, their importance and the satisfaction of the participant. The second part rate what the participant think about the therapy in a 1 to 10 scale. The third part assess what participant feel about the therapy on different scale. Finally, the last part rate satisfaction, preoccupation, stress and what the participant less like about the therapy.

The Evaluation of Treatment Questionnaire is a 19-item subjective measure assessing treatment satisfaction. It is a qualitative and quantitative questionnaire. The first two items assess how far therapy help, their importance and the satisfaction. The second part rate what the participant think about the therapy in a 1 to 10 scale. The third part assess what participant feel about the therapy on different scale. Finally, the last part rate satisfaction, preoccupation, stress and what the less like about the therapy.