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Psychological disorders affect approximately 1 billion people globally and were responsible for 10% of the prepandemic global burden of disease in 2019, with estimates of the mental health burden increasing []. Depression and anxiety disorders cost US $1 trillion per year globally []. Evidence-based, effective mental health care is available, but its provision does not reach everyone who needs it [,].
Digital (or Online) TherapyDigital psychological therapy provides an opportunity to enhance patient access to psychological treatment [,] and is recommended by the World Health Organization as a cornerstone of “comprehensive, integrated and responsive mental health and social care services” []. Research regarding digital therapy has largely focused on internet-delivered cognitive behavioral therapy (CBT), demonstrating its efficacy and cost-effectiveness [,], particularly in the treatment of depression and anxiety [-]. Although uptake and adherence to digital therapy in the research setting have shown improvement [], engagement is still low, particularly in routine mental health care [-]. In addition, research suggests stakeholder preference for face-to-face interventions [,]. A systematic review [] reported on concerns raised by health professionals about the use of digital therapy alone, including perceived nonsuitability for patients due to symptom severity, lack of digital access and literacy, and perception of digital treatment as being less engaging than face-to-face treatments. This review indicated that blended psychological therapy (also called “blended therapy” or “blended care”) was perceived as a midway option between digital and face-to-face therapy.
Blended TherapyBlended therapy (BT) is a model of care that combines digital and face-to-face delivery of psychological therapy, integrating benefits from both modalities. Specifically, the face-to-face component is delivered by a mental health professional, such as a psychologist, while the digital component is patient driven [-]. Integrating digital therapy with face-to-face interventions in a blended model has the potential to save professionals’ and patients’ time (eg, transport to and from the clinic); increase the frequency of sessions; improve treatment uptake, adherence, and maintenance; and boost therapy effects [-].
A systematic review by Erbe et al [] (N=44) found that BT may improve dropout rates and save health professionals’ time compared with exclusively face-to-face interventions. Despite increasing evidence of the benefits of blended psychological therapy for patients [,], there is a lack of research specifically focused on “what, how, where, and when” BT is effective to inform future BT interventions [,,]. The rationale for our systematic review emerges from the scarcity of data specifically focusing on BT processes including BT content and structure, which hinders scientific reproducibility of BT and impacts its implementation success.
Objectives of This ReviewSeeking to address these gaps in BT literature, our systematic review and meta-analysis expands on the work of Erbe et al [] and aims to (1) identify and describe the structure, content, and ratio of the face-to-face and digital components in BT interventions applied for the treatment of psychological disorders and (2) investigate whether there is an association among the structure, content, and ratio of blended components and the treatment efficacy of, uptake of, and adherence to BT.
This review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [] guidelines and was registered with PROSPERO (CRD42021258977). The PRISMA checklist is provided in .
Search StrategyThe PsycINFO, CINAHL, Embase, ProQuest, and MEDLINE databases were searched using keywords and Medical Subject Headings terms—“blended”; “online”; “face-to-face”; “treatment”; “therapy”; “care”; “mental disorders”; “psychological distress”; and “psychological disease”—for articles published in English (). The search included articles published till May 2022, and an updated search was conducted in March 2023. Reference lists of the included studies were also manually searched.
Study SelectionInclusion and Exclusion CriteriaStudies that described or applied an intervention where both digital and face-to-face elements were integrated or delivered sequentially were included. We included studies in which the participants were aged ≥18 years and diagnosed with a psychological disorder. Studies solely investigating populations other than this target group (health care professionals, student cohorts, employees, etc) were excluded.
ComparatorsThe comparator or control groups included treatment as usual (pharmacological or psychological intervention and standard medical care), waitlist, or other interventions.
Data AbstractedThe primary focus was the intervention design, including descriptions of the structure, content, and ratio of the sessions used in each model. Secondary outcomes were (1) a psychological therapy approach used in the BT models, (2) patient groups for which BT was applied, (3) treatment efficacy, (4) uptake and adherence, (5) health service outcomes (eg, cost-effectiveness), (6) patients’ acceptability of BT, (7) therapeutic alliance rates, and (8) barriers and facilitators reported.
Article Screening and SelectionAll search results were uploaded into Covidence software []. Two reviewers (KFN-Z and JMS) screened the titles and abstracts independently. Full-text reviews based on the eligibility criteria were conducted by KFN-Z and PB or JMS.
Data ExtractionData extraction was conducted by KFN-Z using a purpose-designed data extraction template. Extraction results were partially reviewed (6/29, 20%) by a second coder (JMS) to assess accuracy. To capture any missing data, the corresponding authors were e-mailed twice. Data extracted included the following: (1) study characteristics—authors, year of publication, country, study setting, study aims, study type, sample size, control group (where applicable), therapy approach applied, primary or secondary psychological outcomes, and symptom assessment measures and participant characteristics such as age, sex, diagnosed psychological disorders, severity of symptoms, and individual study outcomes; (2) intervention characteristics—BT intervention design based on the structure, content, and ratio of BT sessions; number, periodicity, and duration (in minutes) of face-to-face and digital sessions; treatment length (in weeks); and (3) BT intervention outcomes—treatment efficacy, uptake, adherence, cost-effectiveness, acceptability, therapeutic alliance, and barriers and facilitators to BT reported.
Data AnalysisTo address the objectives of this review, quantitative variables regarding the BT intervention structure were summarized and described. We used descriptive statistics (mean, percentages, and range) to describe quantitative data regarding study and participant characteristics; BT intervention uptake, adherence, and completion rates; treatment length (in weeks); number, time (in minutes), ratio, and periodicity of face-to-face and digital sessions; treatment acceptability; efficacy; and therapeutic alliance. Barriers to and facilitators of BT were qualitatively analyzed using a thematic analysis [] approach. Qualitative data on BT structure and content were analyzed using a content analysis approach []. Categories and subcategories were summarized in a framework that builds on the concepts described by Erbe et al [] ().
Textbox 1. Classification—blended model designs.Interaction between face-to-face and digital components: integrated vs sequential
Integrated models present both the digital and face-to-face components as collaborating parts within a therapy regimen, with both components delivered within the course of the intervention [].Sequential models present the digital component delivered in entirety before or after face-to-face component delivery []. Sequential interventions start by delivering a “batch” of either face-to-face or digital sessions. Once the first “batch” is finished, the other component gets delivered.Stepped care is considered a special type of sequential design in which the digital component is a step in the intervention sequence []. Stepped care interventions deliver the least intensive or costly treatment first and then progress to more intensive or aftercare treatment, if required. Hence, the “blend” in stepped care only effectuates after the first stage (digital) of treatment is complete and if patients require additional (face-to-face) care.Role of the components in the intervention: core vs supplementary
Core components are an indispensable part of the blended intervention, as they deliver new therapeutic elements (ie, modules complement each other).Supplementary components present content that has already been discussed during the intervention, that is, content of one component is supplementary to the content delivered in the main component. For example, face-to-face content may be supplemented by reinforcing exercises and homework on the web.Delivery pattern of face-to-face or digital components: alternate vs case by case
Alternate delivery is a configuration in which each session is delivered by alternating face-to-face or digital components in a fixed ratio. The distribution of components is preset for the entire intervention; this may feature as a 1:1 ratio, but other ratios (eg, 2 digital to1 face-to-face) of distribution are possible.Linear delivery is specific to sequential designs in which all digital sessions are delivered in a row followed by all face-to-face sessions in a row, or vice versa.Case-by-case delivery is a configuration in which therapists assess and formulate a strategy for distributing the face-to-face or digital sessions adapted to the clients’ or patients’ needs on a case-by-case basis.Digital content assignment: personalized vs standardized
Personalized content assignment is not preset; therapists and patients decide which materials to complete, tailoring them to patients’ needs.Standardized content assignment is largely preset; materials are delivered to all patients undergoing treatment with little or no changes to content.Meta-AnalysesAlthough a meta-analysis was not originally included in the registered protocol, data collection and analysis processes indicated the relevance of meta-analyzing treatment outcomes for enhancing systematic review results. The meta-analysis was conducted using the Comprehensive Meta-Analysis program [] to investigate treatment efficacy between the treatment and control dyads. A meta-analysis of BT interventions only was also conducted to investigate associations between BT structure and content and treatment outcomes. Pre-post outcome means and SD, alongside data on sample size at post–time points were included in the analysis. Standardized difference in means (Cohen d) and 95% CIs were used as effect size (ES) measures, and z values were used to test the null hypothesis (ES=0). We used a random effects meta-analysis due to expected heterogeneity. ES was set to negative numbers to show the change in symptoms (the lower the number, the higher the reduction in symptoms). Heterogeneity was assessed using Q test (Q), I-squared (I2), Tau-squared (T2), and Tau (T) scores. Publication bias was assessed using funnel plots and the trim and fill method by Duval and Tweedie [].
Risk of Bias and Quality AssessmentTwo independent reviewers (KFN-Z and JMS) assessed the risk of bias using the National Institutes of Health Study Quality Assessment Tool (quantitative) [], the Critical Appraisal Skills Programme qualitative checklist [], or the Mixed Methods Appraisal Tool [].
Database searches identified 2650 papers after removal of duplicates. Title and abstract screening resulted in 103 articles for full-text review. A total of 30 eligible articles were identified but only 29 were included in the review—one eligible paper was excluded as it reported the same data. The PRISMA diagram in [] provides the details of the process.
Figure 1. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 flow diagram. Quality AssessmentQuality assessment deemed most studies (n=22) to be of “good quality” as they addressed most of the quality assessment criteria applied. Seven articles [,-] were classified to be of “fair” quality ().
Study CharacteristicsOf the 29 articles, 25 (86%) were prospective studies (randomized controlled trials [RCTs], n=14; feasibility or pilot, n=4; cohort or single arm, n=7); 3 (10%) were retrospective analyses of cohort studies; and 1 (3%) study used qualitative methods only. Most BT interventions (22/29, 76%) primarily treated depression, either exclusively (13/29, 45%) or in combination with anxiety treatment (9/29, 31%). Most studies (28/29, 96%) used a CBT approach, with 3 (10%) combining CBT and other approaches such as dialectical behavioral therapy and acceptance and commitment therapy (n=2) and motivational interviewing (n=1). Outcomes assessed were primarily symptom reduction (25/29, 86%), although 4 (14%) studies reported on the intervention process or working alliance outcomes as the primary focus ().
Collectively, the studies included a total of 12,322 (range 3-4448) patient participants, with 57.71% (n=7111) receiving BT interventions. Of the studies reporting on symptom reduction (28/29, 96%), all prescreened for clinical levels of psychological morbidity ().
Table 1. Characteristics of reviewed studies.Study; countryStudy settingStudy aimsStudy designParticipants, N; BTa group, n; comparator, nTherapy type; clinical outcomesAskjer and Mathiasen [], 2021 and Mathiasen et al [],b 2022; DenmarkSpecialized mental health careExplore if WAc predicted treatment outcomesExploratory; secondary analysis from an RCTd76; 38; 38; comparator: F2Fe CBTfCBT; WA, depressive symptomsBerger et al [], 2018; GermanyRoutine outpatient psychotherapy practicesInvestigate web-based treatment as adjunctive to depression treatment vs regular psychotherapyTwo-armed, pragmatic RCT98; 51; 47; comparator: TAUg: psychotherapyCBT; depressive symptomsBisson et al [], 2022; United KingdomPrimary and secondary mental health settingsDetermine if CBT-TFh was noninferior to F2F CBT-TF for PTSDiPragmatic, multicenter, noninferiority RCT196; 97; 99; comparator: F2F CBT-TFCBT; severity of symptoms of PTSDCloitre et al [], 2022; United StatesRoutine care in mental health outpatient clinicsAssess 2 ratios of F2F sessions to self-guided work on trauma-exposed veteransQuasi-experiment with a noninferiority design202; 202; NCjTransdiagnostic, trauma-informed CBT; PTSD and depressionDuffy et al [], 2020; EnglandSpecialized mental health care serviceInvestigate iCBTk as a prequel for high-intensity depression and anxiety treatmentUncontrolled feasibility design (open study)123; 123; NCCBT; anxiety and depression and work and social functioningEtzelmueller et al [], 2018; GermanyRoutine care practice (clinics)Evaluate patient experience of a blended iCBT serviceQualitative, semistructured interviews15; 15; NCCBT; NDl depressionHøifødt et al [], 2013; NorwayUniversity outpatient clinicEvaluate effectiveness and acceptability of a guided web-based program for depressionRCT106; 52; 54; comparator: delayed treatment, waitlist, or TAUCBT; depression symptomsJacmon et al [], 2009; AustraliaPsychology private practiceAssess cost-effectiveness and convenience of partially digital depression treatmentSingle-arm, pretest-posttest study9; 9; NCCBT; depression levelsKemmeren et al [], 2019; France, Germany, Poland, and NetherlandsMultisetting (specialized mental health and routine primary care)Examine use of and engagement to blended CBT for depressionExploratory, secondary study from RCT231; 231; NCCBT; ND depressionKenter et al [], 2013; NetherlandsMental health care center; routine careReport on the uptake of digital treatment, on the profile of patients who prefer digital therapy, and on symptom reduction vs waitlistObservational study (electronic patient database)104; 55; 49; comparator: waitlistPSTm; ND depression, anxiety, and burnoutKenter et al [], 2015; NetherlandsMental health serviceCompare the effects and costs between blended and F2F treatmentsNaturalistic study: examined records of patients4448; 168; 4280; comparator: TAU: F2FCBT; ND depression and anxietyKok et al [], 2014; NetherlandsOutpatient clinicsAssess clinical effectiveness of internet-based guided self-help vs waitlistRCT212; 105; 107; comparator: waitlistPsychotherapy; phobia and avoidance behaviorKooistra et al [], 2016; NetherlandsOutpatient specialized mental health care centerDevelop and evaluate a structured, blended CBT protocol for patients with depressionFocus-groups and single-arm, pre-post30; 9; NC (12 patients)CBT; ND depressionKooistra et al [], 2019; NetherlandsSpecialized mental health care (outpatient services)Compare costs and effectiveness of blended vs standard CBT for depressionPilot RCT with 2 parallel groups102; 53; 49; comparator: CBT-F2FCBT; self-reported depression severityKooistra et al [], 2020; NetherlandsOutpatient specialized mental health clinicsInvestigate WA in bCBTn for depressionExploratory, secondary study from pilot RCT92; 47; 45; comparator: regular CBTCBT; ND depression levelsLungu et al [], 2020; United StatesEmployer programEvaluate the effectiveness of a video-based CBT and internet interventionRetrospective cohort study385; 385; NCCBT+UTPo, ACTp, and DBTq; ND depression and anxietyLy et al [], 2015; SwedenClinical settingEvaluate a blended treatment for depressionNoninferiority RCT93; 46; 47; comparator: F2F BArBA; depressionMånsson et al [], 2013; SwedenClinical settingExplore clinical outcomes and user experiences of internet-delivered therapy. To develop or test a bCBT modelMixed methods, case series, pilot study (pre-post re BT testing)23; 15; NC (patients, n=15; therapists, n=8)CBT; ND anxiety and depressionMånsson et al [], 2017; SwedenOutpatient psychiatric clinicEvaluate an internet-based support as adjunct to F2F CBTFeasibility study54; 45; NC (patients, n=45; therapists, n=9)CBT; ND anxiety and depression symptomsMol et al [], 2018; NetherlandsOutpatient clinicExplore therapist behaviors; adherence; and patient outcome in digital therapyObservational study64; 45; NC (patients, n=45; therapists, n=19)CBT; ND depression levelsNakao et al [], 2018; JapanOutpatient medical institutionsEvaluate effectiveness of web-based bCBT in reducing therapist time in patients with depressionSingle-blinded RCT40; 20; 20; comparator: waitlist + pharmacological treatmentCBT; depression symptomsRomijn et al [], 2021 and Romijn et al [];b NetherlandsOutpatient specialized mental health care centersExplore therapist fidelity to bCBT protocols for anxiety disordersMixed methods (derived from a larger RCT)114; 52; 62; comparator: CBT F2FCBT; anxiety symptomsTarp et al [], 2022; DenmarkPublic municipal outpatient alcohol clinicsDescribe development and testing of a digital program; participant experiences; and usability of BTFeasibility and pilot study32; 22; NC (development: 7 therapists+3 patients)CBT + motivational interviewing; —s (intervention system usability)Thase et al [], 2018; United StatesDepartment of psychiatry of medical schoolsEvaluate the efficacy of computer and therapist-assisted CBT vs standard CBTNoninferiority RCT154; 77; 77; comparator: CBT F2FCBT; depression symptom severityvan de Wal et al [], 2017; NetherlandsCancer hospitals: academic, regional, and outpatientInvestigate the efficacy of BT for FCRt in cancer survivorsRCT: 2-arm, parallel group, longitudinal88; 45; 43; comparator: TAU (any)CBT; FCR severityVernmark et al [], 2019; SwedenMental health care centersExplore patient- and therapist-rated WA in bCBT and WA as a predictor for changeExploratory secondary study from RCTs151; 75; NCCBT; depression levelsWitlox et al [], 2021; NetherlandsMental health service at general practicesExamine the effectiveness of blended ACT for older adults with anxietyRCT (single-blinded)314; 150; 164; comparator: TAU (FTF CBT)ACT; anxiety severityWu et al [], 2021; United StatesEmployer mental health program clinical servicesEvaluate the outcomes of a blended care coaching program for anxiety and depressionRetrospective cohort analysis1496; 1496; NCCBT-based + CBT, DBT, and ACT; anxiety and depression symptomsWu et al [], 2021; United StatesEmployer mental health program clinical servicesExamine the effectiveness and the impact of bCBT on anxiety and depressionRetrospective cohort analysis3401; 3401; NCCBT+DBT and ACT; anxiety and depression symptomsaBT: blended therapy.
bLinked study.
cWA: working alliance.
dRCT: randomized controlled trial.
eF2F: face to face.
fCBT: cognitive behavioral therapy.
gTAU: treatment as usual.
hiCBT-TF: internet-guided cognitive behavioral therapy with trauma focus.
iPTSD: posttraumatic stress disorder.
jNC: no comparator.
kiCBT: internet-delivered cognitive behavioral therapy.
lND: not disclosed.
mPST: problem-solving therapy.
nbCBT: blended cognitive behavioral therapy.
oUTP: unified transdiagnostic protocol.
pACT: acceptance and commitment therapy.
qDBT: dialectical behavioral therapy.
rBA: behavioral activation.
sNot applicable.
tFCR: fear of cancer recurrence.
Primary outcomes of individual studies included efficacy or effectiveness (14/29, 48%) [-,,,,,,, ,,-]; working alliance (3/29, 10%) [,,]; usability and uptake (3/29, 10%) [,,]; feasibility (2/29, 7%) [,]; and patient or therapist (4/29, 14%) [,,,] experience. One (4%) study [] explored multiple primary outcomes of therapeutic alliance, compliance, and symptom reduction, and 2 (7%) studies [,] reported dual outcomes of efficacy and cost.
Table 2. Patient participants’ characteristics.StudyAge (y), mean (SD); rangeFemale, n (%)Pre-post time points, assessment tool, psychological symptoms per group: mean (SD) and severity at baselineAskjer and Mathiasen [], 202135 (13.96); 18-7156 (74)Baseline and 12 wkaPHQ-9: Patient Health Questionnaire-9.
bBT: blended therapy.
cBDI-II: Beck Depression Inventory II.
dGAD-7: Generalized Anxiety Disorder-7.
eCAPS-5: Clinician-Administered Posttraumatic Stress Disorder Scale for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.
fPTSD: posttraumatic stress disorder.
gPCL-5: Posttraumatic Stress Disorder Checklist for the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.
hNot available.
iiCBT: internet-delivered cognitive behavioral therapy.
jQIDS-16-SR: 16-Item Quick Inventory of Depressive Symptomatology, self-reported.
kBAI: Beck Anxiety Inventory.
lHADS: Hospital Anxiety and Depression Scale.
mMBI: Maslach Burnout Inventory.
nGAF: Global Assessment of Functioning.
oFQ: Fear Questionnaire.
pCES-D: Centre for Epidemiologic Studies Depression Scale.
qIDS-SR30: Inventory of Depressive Symptomatology Self-Rated.
rMADRS-S: Montgomery Åsberg Depression Rating Scale—self-rating version.
sGRID-HAMD: 17-item GRID-Hamilton Depression Rating Scale score.
tHDRS: Hamilton Depression Rating Scale.
uCWS: Cancer Worry Scale.
Classification of BT ModelsOn the basis of the models defined by Erbe et al [], the majority (26/29, 90%) of the studies reported an integrated intervention design, where new therapeutic content was delivered either (1) across both the face-to-face and digital modalities (core; n=14) or (2) primarily using one modality (usually the face-to-face component) with additional content delivered as supplementary material (n=12). Integrated interventions were the most common designs for addressing depression (n=14) and depression and or anxiety (n=8). Three studies were classified as sequential designs and described a core role for both face-to-face and digital components. One sequential model was delivered as stepped care in which most patients received digital therapy only.
BT delivery was further differentiated based on whether both components were delivered in a preset, alternate format or a tailored, case-by-case arrangement. Most integrated interventions (17/26, 65%) used an alternate delivery format. Therapeutic content within integrated and alternate designs had either core (9/17, 53%) or supplementary (8/17, 47%) roles.
In 19 (65%) studies, patients engaged with digital content following a standardized program with minimal tailoring of the materials presented. In contrast, 10 (35%) studies described a more personalized manner of assigning or interacting with digital content where the therapist and patient have more autonomy to choose, change, or create digital content according to individual need. An overview of model classifications is presented in .
Table 3. Blended therapy model classification per study.StudyInteraction of F2Fa and digital componentsRole of F2F and digital componentsPattern of delivery of F2F and digitalDigital content delivery
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