Primary outcome measure
The primary outcome measure is
symptoms of depression as assessed with the Patient Health Questionnaire-9 (PHQ-9) [
46]. The PHQ-9 is a nine-item mood module that can be used to screen and to diagnose patients with depressive disorders. The 9 items are each scored on a 0–3 scale, with the total score ranging from 0–27 and higher scores indicating more severe depression. The PHQ-9 has shown to have good psychometric properties [
47,
48].
The Quick Inventory of Depressive Symptomatology Self-Report (QIDS-16-SR) is used in addition to the PHQ-9, because this measure is more often used (especially in specialised mental healthcare) and therefore makes better comparison with other studies possible. The QIDS assesses
depression severity and consists of 16 items (each item scores 0–3, total range 0–48), with higher total scores being indicative of a higher severity of depressive symptoms. The QIDS includes symptom domains of MDD based on DSM-IV and Research Diagnostic Criteria (RDC). The QIDS has shown highly acceptable psychometric properties, with internal consistency of α = .86 [
49]. The cut-off points of 6, 11, 16 and 21 represent the thresholds for mild, moderate, severe and very severe depression, respectively.
Secondary outcome measures
A diagnosis of depression will be assessed with section A and B of the
MINI International Neuropsychiatric Interview (M.I.N.I.) version 5.0, a structured diagnostic interview based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and on International Classification of Diseases (ICD-10) criteria [
37]. In comparison with the patient-rated version of the SCID, the M.I.N.I. achieved a good Kappa score of 0.84 with a sensitivity of 0.96 and a specificity of 0.88 in diagnosing Major Depressive Disorder (MDD) [
50].
The full M.I.N.I., with exception of section M (Anorexia Nervosa), N (Bulimia nervosa), and P (Antisocial personality disorder), will be conducted at baseline (T0) to determine lifetime and current depression, as well as current comorbid psychiatric. At 12 month follow-up (T3), the depression, anxiety and PTSD sections of the M.I.N.I. will be assessed again, covering the past 12 months.
Demographic variables including age, sex, ethnicity, marital status, educational level and employment status, as well as history of treatment for mental health problems will be assessed at baseline. In addition, patients will be asked about treatment preference, indicating which treatment alternative they prefer (bCBT or TAU) before being allocated to one of the two conditions.
Patients’ expectancy of treatment will be assessed after randomisation with the Credibility and Expectancy Questionnaire (CEQ). This questionnaire consists of six items measuring expectancies toward the therapy and the credibility of treatment options. The items are scored on one of two scales, one 9-point Likert scale ranging from 0 (not at all) to 9 (absolutely) or a continuous scale ranging from 0 % (not at all) to 100 % (absolutely). The sum score on credibility and expectancy can vary between 3 and 27, with higher scores being indicative of more positive attitudes. Both factors (credibility and expectancy) have shown to be stable across different populations, with high internal consistency within each factor [
51].
Locus of control will be assessed with the 5-item version of the Sense of Mastery Scale [
52], with proven good reliability [
53]. Questions are scored on a Likert-scale ranging from 1 (‘totally disagree’) to 5 (‘totally agree’). The total score ranges from 5 to 25, with higher scores being indicative of a higher degree of perceived control. The Sense of Mastery Scale will be administered at all time points (T0-T3) to assess changes in locus of control.
Patient’s satisfaction with the treatment will be assessed with Client Satisfaction Questionnaire (CSQ-8), used to measure global patient satisfaction [
54]. The questionnaire consists of 8 items that are measures on a 4-points scale. Total scores range from 8 to 32, with higher scores being indicative of higher levels of satisfaction. The CSQ-8 has high internal consistency of α = .93 [
55].
Satisfaction with the online platform will be evaluated with the System Usability Scale (SUS), a simple 10-item questionnaire giving a global view of subjective assessments of usability of a technology system [
56]. All items are measured on a 5-point Likert scale ranging from ‘strongly disagree’ to ‘strongly agree’. Total SUS scores have a range from 0–100. The questionnaire was found to be reliable and robust [
57]. The SUS has to be completed by patients receiving bCBT only, and once per therapist three months after starting with their first blended treatment.
The
therapeutic alliance between therapists and patient will be assessed with the short version of the Working Alliance Inventory (WAI-SF) [
58], Dutch version [
59]. The WAI-SF is a 12-item self-report questionnaire with responses on a 5-point Likert scale ranging from’never or rarely’ to ‘very often’. The questionnaire covers three dimensions of working alliance: 1) therapeutic goals, 2) tasks, and 3) bond. The subscales have shown to have good internal consistencies (α > .80). Both the patient and the therapist version of the questionnaire will be administered at T1, to determine the quality of the therapeutic alliance.
The alliance between the patient and technologies will be assessed with an adapted version of the WAI: the Working Alliance Inventory – Online Therapy, developed by Labpsitec (Labority of Psychology and Technology). The items address goals and tasks agreement with the online treatment program, and not with the therapist.
To assess possible
negative side-effects of the treatment, the Inventory of Negative Effects of Psychotherapy (INEP) [
60] will be administered at T2 (6 months after baseline). The version used in this study consists of 15 items, assessing a range of common changes participants experienced in line with their therapy, concerning their social and work environment. The following domains are covered: negative interpersonal changes, negative effects in an intimate relationship, family/friends, perceived dependence from therapist, stigmatisation. All items are rated on a 4-point Likert scale. For each item, respondents also state whether they attribute the adverse effects on the therapy or on other circumstances. Only item scores of those negative effects that were attributed on the therapy are added to the total score. Higher total scores indicate more negative effects. The INEP shows an internal consistency of α = 0.85 [
60]. For the use in this study, the questionnaire was translated by the forwards-backwards method, i.e. the questionnaire was first translated from English into Dutch by two persons who reached consensus by discussion. Next, the questionnaire was translated back to English and was compared with the original questionnaire.
Economic evaluation
Quality of life will be determined with the five-level version of the EuroQol (EQ-5D-5L), a self-report questionnaire assessing the health related well-being of participants [
61]. The questionnaire consists of five items: mobility, self-care, daily activities, discomfort and mood state. Each item has five response categories ranging from ‘no problems’ to ‘a lot of problems’ [
62]. Furthermore, this scale contains a visual analogue scale concerning health state. The EQ-5D-5L health states will be converted to utility scores using the Dutch tariff. Quality-adjusted life-years (QALYs) will be calculated by multiplying the utility of a specific health state by the time spent in that health state. Changes in health states between measurements will be linearly interpolated. The EQ-5D-5L holds acceptable levels of content validity [
63] and has demonstrated valid redistribution, reduced ceiling, and improved discriminatory power and convergent validity compared to the EQ-5D-3L [
64].
Health care utilisation and
productivity losses due to illness will be measured using an adapted version of the Trimbos and iMTA Questionnaires on Costs Associated with Psychiatric Illness (TiC-P), a self-report questionnaire consisting of two different parts that can be administrated separately [
65]. Part I will be used to assess the participants’ healthcare utilisation and medication use. Part II (short form Health and Labor Questionnaire; SF-HLQ) consists of 11 items measuring lost productivity costs resulting from absenteeism (being absent from work because of illness) and presenteeism (being present at work while ill which may lead to reduced efficiency).
Engagement and usage measures for bCBT
Activities on the platform such as number of visits, time in-between logins and number of messages exchanged between patient and therapist, will be assessed through track and change functionalities (log files). Data on how patients use online modules (frequency, duration, order, completion), how they rate them and to what extent they adhere, will also be obtained through usage statistics on the Moodbuster online treatment platform.
Patients receiving the blended treatment will as part of the treatment protocol additionally fill out the PHQ-8 at the end of each module, for monitoring treatment outcome (i.e., all items on the PHQ-9 scale except the ninth item). As this data is being gathered in a self-administered fashion and direct action on positive responses on the ninth item inquiring “thoughts that you would be better off dead or of hurting yourself in some way” is not feasible, it was chosen to exclude this item. Patients are instructed to use existing services of the mental health care organisations when they feel the need to contact a doctor or a therapist outside working hours. The PHQ-8 has similar operating characteristics as the PHQ-9 (sensitivity, specificity, and positive predictive value), regardless of the threshold [
38].