Study design
This is a prospective cohort study with convenience sampling, where treatment is not under the control of researchers but the sampling is based on a convenience sampling method. Inclusion criteria: We will include all adolescents attending grades 7 to 9 (age 13 to 16 years) in selected schools. Exclusion criteria include psychiatric care within the past 12 months or receiving a psychosocial intervention (psychotherapy, IPC-A, any other therapy or support for depression from the same professional for > 3 meetings) during the 12 months before baseline, an inability to reliably understand the Finnish, Swedish, English, or Finnish plain language versions of the survey, not having access to digital devices to respond to a follow-up survey, or an adolescent’s or caretaker’s report on need for exclusion, such as another medical condition – including a mental disorder – where current active treatment could be endangered by research. Exclusion will be made by the researcher based on the survey response from the adolescent and caretaker.
Recruitment and eligibility
The recruitment of adolescents will be done from four university clinic areas (Northern, Eastern, Central and Western Finland) to provide a representative national sample based on interest of schools. Two to three municipalities from each university clinic area have consented to the study.
With the consent of the school, all grade 7 to 9 adolescents (age about 13 to 16 years) in the school will have a session about mental health literacy skills (how to talk with friends about mental health, how to know when help by an adult is needed). The information will be adjusted for their age. During that session, the goals of the study will also be described. A similar session will be held for caretakers; the session will be complemented by messaging all parents a link to a video recording and supplementary materials for mental wellbeing online, as well as providing information about the study.
Subsequently, a research assistant (RA) will help adolescents fill in a digital survey questionnaire. Upon agreement with the recruiting school, this can take place either after the information session or in the classroom, in a context of a group discussion at a general level about the dimensions of mental health and wellbeing, and options for help for mental health.
Sample size
To estimate the number of adolescents to be screened, in the absence of available Finnish data, we used the information from the Netherlands Mental Health Survey and Incidence Study (NEMESIS) for incidence [48] and prevalence findings from NEMESIS [49]. Based on these findings, we roughly estimated that the incidence of depressive disorders would be 2% [18].
For the current study, a conservative estimate is to screen 6 000 to 9 000 young people. We estimate this, with a 15% prevalence and 2% incidence, approximately 50% of adolescents not having previous treatment despite prevalent depression at baseline to the cohort, and a 70% consent rate, to be sufficient to recruit a minimum of 100 consenting adolescents to the IPC-A group, 200 consenting adolescents to TAU-group, and 100 to the depressed/no treatment-group. The size of any group might be considerably larger, but we will finish recruitment once the minimum size of all groups has been reached. Enriching the sample for IPC-A using recruitment by IPC-A-professionals will be done if the sufficient sample size for IPC-A cannot be reached with convenience sampling.
Measures and data collection
Data will comprise surveys for adolescents, caretakers, and therapists, as well as register data and, where necessary, complementary information from medical files on the timing, duration, and content of psychosocial support and overall treatment of depression (Table 1). The respondents will receive an online link to respond at their convenience. We will not have in-person meetings after recruitment and informed consent.
Table 1
Study flow and timing of data collection
| Timing |
Data source | Intake | 3 months | 6 months | 12 months | 2, 5, and 10 years |
Comprehensive student survey | All | All | All | If sustained depression over 6 first months (PHQ-9-A ≥ 10 twice) | - |
Biweekly short student survey | x | x | x | - | - |
Caretaker’s survey | x | | x | - | - |
Therapist’s survey | | | x | - | - |
Intensity of treatment | Medical files, adolescent, caretaker and professional’s report | - |
Register data | | | | | x |
A comprehensive adolescent survey
Adolescents will complete a survey on sociodemographic information and self-evaluation measures at baseline, at 3 and 6 months. Those who show sustained depression (Patient Health Questionnaire 9 items, adolescent version (PHQ-9-A) sum scores ≥ 10 twice during the first 6 months after baseline) will also complete the comprehensive survey at 12 months. The comprehensive adolescent survey is available as a shorter version in plain Finnish language, based on the decision of school personnel.
Outcome measures in the adolescents’ and caretakers’ surveys
We list here the self-report questionnaires (Table 2) that will be presented to adolescents and caretakers at the various timepoints. The questionnaires will be presented in Finnish, Swedish, or English, as suitable.
Table 2
A summary of the content of the adolescents’ and caretakers’ surveys
Name of the scale | Short | Length | Rating | Time frame | Describes |
The Patient Health Questionnaire 9 items, adolescent version*1 | PHQ-9-A | 9 items | 0 to 3 | 2 weeks | Depressive symptoms |
The child-friendly EQ-5D version*1 | EQ-5D-Y | 5 items + VAS | 5 items 0 to 2; The EQ VAS | The same day | Quality of life |
Generalized Anxiety Disorder Scale-7 | GAD-7 | 7 items | 0 to 3 | 2 weeks | Anxiety |
Young Person's Clinical Outcomes in Routine Evaluation-Outcome Measure | YP-CORE | 10 items | 0 to 4 | 1 week | Response to therapy |
Do you feel lonely?1 | | 1 item | 0 to 4 | No time frame | Perceived loneliness |
The short Warwick-Edinburg Mental Wellbeing Scale | SWEMWBS | 7 items | 0 to 4 | 2 weeks | Positive mental health |
Experiences of Social Inclusion Scale | ESIS | 10 items | 0 to 4 | No time frame | Social inclusion |
3x10D Survey* | 3x10-D | 10 items | 0 to 10 | No time frame | Functionality |
Questions about worry as well as need for help*1 | | 0 to 10 VAS scales | 0 to 10 VAS scale | No time frame | Need and motivation for professional help |
Motivation for Youth’s Treatment Scale | MYTS | 8 | 1 to 5 | No time frame | Motivation to psychotherapy |
Other questions |
Questions from the Finnish School Health Promotion survey* | | | Yes/no, open field | Current 12 months | Sociodemographic information, minority status Alcohol and substance use, self-harming behavior*1 |
Use of health and social welfare services*1 | | | Yes/no, open field | 12 months | Information to classify as IPC-A, TAU, and no treatment groups |
Content and overview of treatment*1 | | 2 + 10 | yes/no, open field; 10 statements true/false | During the intervention | Benefits and adverse effects due to treatment, safety of contact* |
Note. Scales marked with an asterisk (*) will be used in the caretaker’s survey as a proxy version. Scales marked with 1 will be included in the shorter plain language version.
The Patient Health Questionnaire 9 items (PHQ-9) is a depression severity measure based on DSM criteria. The items are answered according to the frequency of symptoms (0 = not at all, 1 = some days, 2 = more than half of the days, 3 = almost every day). A higher score is indicative of greater depressive symptomatology. The PHQ-9 is a unidimensional measure with good internal consistency, also in adolescents [50–53]. In adults, the optimal sum score cut-off is ≥ 10 [54]. The PHQ-9 classifies respondents’ sum scores into depression severity as follows: 0–4 indicates no depressive symptoms, 5–9 mild depressive symptoms, 10–14 moderate depressive symptoms, 15–19 moderately-severe depressive symptoms, and 20–27 severe depressive symptoms [54]. One study of 442 youth with major depressive disorder (aged 13–17 years) proposed a cut-off of ≥ 11 [50]. We will use the PHQ-9-A version ≥ 10 according to DSM-5 criteria, including irritated mood for adolescents.
The child-friendly EQ-5D version (EQ-5D-Y) is based on the EQ-5D-3L, which is a widely used standardized generic measure of health-related quality of life (HRQoL), originally designed for adults. EQ-5D-3L has been used internationally in many settings, such as in clinical trials and population surveys. The EQ-5D-Y was introduced by the EuroQoL Group in 2009 as a more comprehensible instrument suitable for children and adolescents than the original [55]. The EQ-5D consists of five questions about mobility, looking after oneself, doing usual activities, having pain or discomfort, and feeling worried, sad, or unhappy. Each item has three response alternatives. A question about general health is evaluated on a visual analogue scale (VAS) [56].
The Generalized Anxiety Disorder Scale-7 (GAD-7) is a seven-item self-rated instrument used to assess symptoms of generalized anxiety. Each item asks the individual to rate the severity of his or her symptoms over the past two weeks. Response options are 0 = not at all, 1 = several days, 2 = more than half the days, 3 = almost every day. GAD-7 scores can be categorized into mild, moderate, and severe anxiety with sum cut-offs of 5, 10, and 15 (score range 0–21). At a cut-off point of 10 or greater, sensitivity and specificity exceed .80 [57]. The adult version has shown adequate psychometric properties among adolescents in clinical [58] and the general population, with a reliability .9 of the sum score [59].
The Young Person's Clinical Outcomes in Routine Evaluation-Outcome Measure (YP-CORE) is a ten-item measure designed for use in the 11–16-year age range. It is adapted for young people from The CORE-Outcome Measure for adults that has both 34- (CORE-OM) and 10-item versions (CORE-10) [60]. The CORE-OM and CORE-10 were developed as screening measures for psychological distress, including items for well-being, psychological symptoms, functioning, and risk. YP-CORE is well accepted, and the rate of missing values is low. Internal consistency (α = .83–.92) and test-re-test reliability is good (r = .69), and the results of confirmatory factor analysis (CFA) have supported a one-factor model. The YP-CORE showed good concurrent validity against two widely used symptom-specific measures (r = .62–.87). The measure was sensitive to change, showing a larger effect size (d = .55) than the Beck Depression Inventory (BDI-21) and Beck Anxiety Inventory (BAI) (d = .31-.50). The Finnish translation of YP-CORE has good psychometric properties [61].
Perceived loneliness is a simple measure of loneliness based on self-assessment including only one question. This single question has been found to have good content validity in older adults [62].
The Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS) with both its 14- and short 7- item versions measures positive mental health, that is, holistic aspects of wellbeing, namely eudemonic and hedonic wellbeing as well as psychological functioning [63]. This questionnaire allows for measuring mental wellbeing as a partially separable concept from mental illness, and has favorable psychometric properties, especially an approximate normal distribution in the general population. We will use the 7-item version (the Short WEMWBS; SWEMWBS) that has been validated in a large Finnish dataset [64], and validations in adolescents have proved successfull [65–67]. Using the SWEMWBS, we will be able to calculate mental health costs and quality-adjusted life years (QALYs) [68].
Experiences of Social Inclusion Scale (ESIS) is a brief self-evaluation instrument to assess self-reported experiences of social inclusion. It consists of ten statements that map the respondent's feelings of belonging, the significance of what they do, and the possibilities for action. One extreme of the continuum formed by the answers represents the experience of non-participation/social exclusion and the other the experience of inclusion. The participation indicator is calculated by scoring claims: a higher score means a stronger experience of inclusion. The sum score is scaled to a range of 0‒100. ESIS has been developed in the Finnish Institute for Health and Welfare (THL) Social Inclusion Coordination Project (Sokra). The theoretical framework is the capability approach (CA). In the validation study of the Finnish version of ESIS in adults, results indicated good internal reliability and consistency (α = .89), and factor analyses suggested a one-dimensional factor structure for the ten items of the ESIS [69]. Validation in younger adolescents is missing.
Functionality (3x10D Survey). The 3x10D survey is a quality-of-life mapping metric. The instrument comprises ten dimensions describing the life situation. The dimensions are evaluated in relation to the present moment, their importance, and the future. The young person evaluates areas of life for how important they feel the dimensions are and how satisfied they are with their current state [70]. The scale is awaiting international validation but publications from Finnish datasets are in preparation.
Sociodemographic information
The comprehensive survey will include sociodemographic information collected at baseline after informed consent and will include information on age, self-identified gender, sex assigned at birth, first language, other minority status (language, sexual orientation, ethnic, other), area of residence, and household composition. The questions are the same or modified from the SHS. Register data will complement and verify responses.
Biweekly short survey
Adolescents will respond to a short online survey biweekly over a 6-month follow-up, independent of their mood. This short survey will include PHQ-9-A and questions on their subjective need for help, as well as any received treatment of depression.
Motivation to treatment
Need and motivation to treatment will be asked: Are you worried about your mood (yes/no). Those worried about their mood will further be asked: How willing are you to have help from others to improve your mood? This is done with a VAS with a scale from 1 to 10. This is complemented by the Motivation for Youth’s Treatment Scale (MYTS) [71], an intrinsic treatment motivation scale for youth. The questionnaire includes 8 questions answered on a scale from 1 (strongly disagree) to 5 (strongly agree), where higher ratings indicate higher motivation. Based on the participants’ answers a total scale and two subscales: Problem Recognition (4 items) and Treatment readiness (4 items) are calculated. The internal consistency of all three scales in young people was found to be good (α = .84 – .89) and Confirmatory Factor Analysis supported the two-factor model [71]. These findings were also replicated in another study, although caution in using the sum score is warranted due to low correlation between the subscales [72].
Caretaker’s survey
One caretaker, upon acceptance and choice of the adolescent, will be sent a link to consent to and twice fill in a survey using a secure link (within one month from baseline and at 6 months from baseline) (Table 2). The caretaker survey will include sociodemographic information. The scales in the caretaker survey include proxy versions of the PHQ-9, EQ-5D-Y, and 3x10D questionnaires, and questions about the adolescent’s mood, need for treatment, and willingness for treatment. We will also ask whether they or the adolescent have sought and received help for the adolescent, and if yes, what kind of support they received; or if not, what kind of support they think would be necessary. At 6 months, where applicable, we additionally ask about benefits and adverse effects of treatment.
Benefits and adverse effects due to treatment
Benefits and adverse effects due to treatment will be estimated with open field questions for the adolescent (“Do you feel that attending interpersonal counseling was useful for you?” (yes/no), Do you feel that attending interpersonal counseling was harmful for you? (yes/no), "If yes, please describe how”. Open field responses will be analyzed with thematic analysis. Ten additional statements concerning experience about treatment were formulated by the team. This format was selected while valid and gold standard instruments for evaluation of adverse effects of therapy have been reported to be lacking [73]. The comprehensive survey at 3, 6 and 12 months contains items for potentially adverse effects (substance use and self-harm). To complement adolescent view, we will ask about benefits and adverse effects in the caretaker and professional’s survey with similar questions.
Adolescent follow-up after 6 months
A comprehensive adolescent survey will be repeated at 12 months for those who show sustained depression; no further follow-up will be done for those who were not depressed over 6 months.
A depressed adolescent in subjective need for treatment is an adolescent who reports a need for help or treatment of depression, and depressed adolescents who received treatment are those who over 6 months report receiving treatment, for whom the caretaker report at 6 months indicates treatment of the adolescent for depression, or where register data shows contact to social or health care services. This information might be complemented from medical records, therapist reports, and/or phone calls to informants, if necessary.
Adolescents with sustained depression (self-reported PHQ-9-A ≥ 10 twice over 6 months, including intake) will be classified in three groups for further follow-up
(1) Adolescents who received prevention or treatment of depression including IPC-A during 6 months of follow-up as reported by the adolescent or a therapist, or evident from the medical files (aiming at n = 100 recruited in order of identification). If IPC-A is started within six months of the follow-up as reported by the adolescent or a therapist in medical files, the adolescent will be classified into this group (1)
(2) Adolescents who received any other treatment for depression (TAU) (aiming at n = 200).
(3) Adolescents with sustained depression, with no treatment at baseline or during six months of follow-up (aiming at n = 100)
The therapist survey
The information collected with therapist surveys at 6 months in case the adolescent reports a contact with a professional for help in depressive symptoms is summarized in Table 3. The surveys include content for all professionals to be responded once. Professionals with a training in IPC-A respond once a survey on implementation support. Finally, all professionals respond a survey after each treatment period per adolescent, and IPC-A-therapists only describe some content specific for IPC-A intervention of the adolescent.
Table 3
A summary of the content of the therapist’s survey
Characteristic or name of the scale | Short | Length | Rating | Time frame | Describes |
A single therapist survey for all therapists |
Sociodemographic status | | 3 questions | Multiple choice | No time frame | Gender, age, maternal language |
Equality | | 6 questions | Multiple choice | No time frame | Place of birth, minority status, language skills, working with a therapy interpreter |
Skills | | 9 questions | Multiple choice | Currently | Professional training, complementary IPC training, working experience |
Professional skills and competence | | 12 items | Sufficient, some, insufficient, not relevant for my work | No time frame | Professional skills in evaluating and supporting subgroups of adolescents |
Trainee Current Practice Report | TCPR | 22 items | 0 (disagree) to 5 (fully agree) | No time frame | Therapist’s subjective skilfullness and difficulties in therapy work |
A single survey for IPC-A therapists |
Normalization Measure Development questionnaire | NoMAD | 20 items | 5-Point Likert Scale | No time frame | Implementation process and support |
Provider REport of Sustainment Scale | PRESS | 3 items | 0 (disagree) to 4 (fully agree) | No time frame | Sustained use of IPC-A |
All professionals respond per each study participant with treatment of depression (IPC-A or TAU) |
The flow of therapy | | Collected per each session | Date, PHQ-9-A-score | | ”Dosing”of and response to therapy |
Content of therapy sessions | | 17 statements | Yes/no | | Content of intervention |
Response to therapy | | | | | |
Benefits and adverse effects of treatment | | 2 statements | Yes/no, open field | No time frame | Beneficial and harmful impact of therapy |
Therapeutic relationship | | 10 opposite statements | Suitable statement chosen | During the intervention | Professional’s view on adolescent experience about interaction (corresponds to adolescent and caretaker surveys) |
The short Warwick-Edinburg Mental Wellbeing Scale | SWEMWBS | 7 items | 0 to 4 | 2 weeks | Professional’s positive mental health |
Professionals will respond in case the adolescent received IPC-A |
Correspondence of the adolescent’s IPC-A intervention as compared to the IPC-A manual, professional’s evaluation | | 20 statements | 0 (disagree) to 2 (fully agree) | After IPC-A intervention | Therapist’s reflection on content as compared to the IPC-A-manual |
| 6 opposite statements | Suitable statement chosen |
A single therapist survey for all therapists
This survey will be sent to the therapists providing the main psychosocial support, including therapists providing IPC-A and other therapists. The survey will include information on their sociodemographic details, professional training, and specifically, the amount and quality of the training they have had in IPC-A or other psychotherapy.
We will use the Trainee Current Practice Report (TCPR), which is a comprehensive self-report questionnaire on competence [74]. TCPR was developed to assess how therapists develop during their training. The questionnaire features items gauging both subjective skillfulness (10 items) and difficulties (12 items) in therapy work. In the Finnish arm of the SPRISTAD study, the data of 267 psychotherapist trainees (representing various background professions, therapy training programs, and universities) has yielded good reliabilities (α = .89 and .84) for the two scales, respectively [74].
A single survey for IPC-A therapists
The NoMAD questionnaire is a set of 20 survey items that assess the implementation process from the point of view of professionals in healthcare [75]. The NoMAD instrument has shown good internal consistency (α = .89 to .921) and face validity in earlier studies conducted in the Netherlands [75–77]. The validation of the Finnish translation remains to be done in this study.
The PRESS consists of 3 survey items, and is designed to measure success of implementation in the sustainment phase [78]. PRESS showed excellent internal consistency (α = .947) in Rasch analysis (Person Separation Index of .826) [78]. The validation of the Finnish translation remains to be done in this study.
Finally, concerning each IPC-intervention with an adolescent, the professional will outline the correspondence of the adolescent’s IPC-A intervention as compared to the IPC-A manual; the 20-statements evaluation form was comprised based on the Finnish IPC and IPC-A manuals [79].
All professionals respond per each study participant with treatment of depression (IPC-A or TAU)
The therapist will report the timing of therapy sessions, content of the intervention and response, including benefits and adverse effects of the intervention. Finally, the professional will complete the 7-item SWEMWBS to assess their own positive mental health each time they respond to a survey concerning a participating adolescent.
Description of the intensity of treatment
Description(dosing) of TAU and IPC-A will be based on the adolescent’s, caretaker’s and therapists’ reports. Where necessary, the information might be complemented from medical records, and/or phone calls to informants. This helps in defining the adolescents as three groups (those who received IPC-A, TAU or no treatment), describing the overall use of resources, and calculating intervention cost for cost-effectiveness analysis at 12 months.
PHQ-9-A during the IPC-A intervention. We do not control provision or timing of IPC-A intervention as part of the study. However, adolescents in the IPC-A group will, even if the treatment period continues after six months, complete weekly reports of PHQ-9-A as it is an integral part of treatment, and this information will additionally be collected for the purposes of the study. Thus, even if IPC-A would continue after 6 months after baseline, we will be able to evaluate the response over the IPC-A period.
Register data
Register data will be collected to define health and social care service use and costs. Register-based data will include 12 months prior study to evaluate pre-trends of service use and costs. A further prospective register-based data collection for economic analysis will be done at 2 years, 5 years, and 10 years after baseline.
We will use four Finnish nationwide registers provided by THL: 1) Care Register for Health Care, 2) Register of Primary Health Care visits, 3) Care Register for Social Welfare, and 4) Register of Child Welfare. In addition, we will use the Drug Prescription Register (Statistics on reimbursements for prescription medicines and rehabilitation) from the Social Insurance Institution of Finland (Kela). The data extracted will include use of emergency services and hospitalizations, which might be due to suicidality, somatic complications from self-harm, or for psychiatric indications. Registers also cover use of inpatient and outpatient services, use of primary care, reimbursements for medicine expenses, provision of psychotherapy or neurocognitive rehabilitation, committed suicides, use of child welfare services and use of social services.
Outcome measures comparing three groups of adolescents with sustained depression (IPC-A, TAU or no intervention)
Primary outcome measure
- proportion of adolescents referred to specialized psychiatric services during 12 months after baseline
Secondary outcome measures
- proportion of adolescents with any need for psychosocial or psychiatric treatment or social services at 2, 5, and 10 years after baseline.
- longitudinal changes in PHQ-9-A score by 12 months in each of the three groups in the repeated adolescent surveys
- EQ-5D
- GAD-7
- YP-CORE-OM
- loneliness
- SWEMWBS
- ESIS
- 3x10D Survey
Complications and harmful behavior during the intervention (surveys and register data)
- alcohol and substance use
- self-harming behavior and suicidality
- hospitalizations during a therapeutic intervention
- drop-out from treatment
All analyses will be intention-to-treat, though loss to follow-up will be minimal, due to the outcome measures being comprehensive national registers. Cost-effectiveness will be estimated at 12 months and economic evaluation will be completed at 2 years, 5 years and 10 years after baseline.
Statistical analysis
Statistical analysis of psychometric measures
For descriptive purposes, we will use both parametric and non-parametric descriptive statistics. Tests for non-parametric measures will be used for testing statistical significance of correlations and between-group differences (IPC-A, TAU, no treatment), with the alpha level set to .05 in each analysis separately. Conventional psychometric characteristics of all measures will be described and compared between self-identified cis-male and cis-female participants. If the size of a subsample is > 20, we will additionally evaluate adolescent groups by gender, sexual orientation, report of ethnic and other minority status, specific groups of first language, or plain language.
To evaluate the validity of each scale, we will analyze the proportion of missing responses. Since there is some indication about limited measurement precision among adolescents for some response options [80], we will use item response theory (IRT) or similar methods to take into account separate probabilities for response option of each item. In the psychometric analysis of the individual scales, we will use confirmatory factor analysis of categorical items to test for psychometric properties. We will also correlate PHQ-9-A with each of the other scales (GAD-7, YP-CORE, perceived loneliness, WEMWBS, EQ-5D-Y, ESIS, and 3x10D Survey). In the longitudinal survey dataset (baseline, bi-weekly measurements over 3 months, comprehensive surveys at baseline, 3, 6, and 12 months), we will estimate test-retest reliability and sensitivity to change of the scales by observing change in PHQ-9-A in relation to changes in other scales.
We will correlate adolescents’ responses with caretaker and professional responses and use caretaker and professional responses to verify and complement adolescent responses. The bi-annual SHS is a national survey, with the last round completed in spring 2023. Where possible, we have included the same questions as the SHS and will thus be able to estimate how representative our cohort is compared to mean values in the municipality.
Statistical analysis of primary and secondary outcomes
In the analysis for outcome and predictors of outcome, after observing the data, we will use propensity score matching to balance for systematic differences between treated and non-treated adolescents. We will compare adolescents in three groups (IPC-A, TAU, or no treatment group, as defined at 6 months). Follow-up with surveys will continue for up to 12 months and with register data for up to 10 years.
We will use PHQ-9-A at baseline and mixed linear modelling for individual outcome for PHQ-9-A during the 6 months of follow-up and test whether the three groups (IPC-A, TAU, and no treatment) differ in variation of symptom severity and outcome in follow-up.
Predictors
We will further describe what adolescent characteristics are predictors of motivation for help (expressed in bi-weekly surveys or MYTS), need for help as expressed by the caretaker, of seeking treatment (bi-weekly surveys), or actually receiving treatment or psychiatric specialized care, or complications and harmful behavior during the intervention (hospitalization, suicide attempt, suicide, severe criminal behavior, or decision on the placement or taking into care by child welfare services). Predictors include sociodemographic factors, baseline symptoms (PHQ-0-A, GAD-7), positive mental health (SWEMBS), functionality and quality of life (YP-CORE, EQ-5D-Y, 3x10D Survey), as well as protective and risk factors (ESIS, perceived loneliness). We will also evaluate whether membership in some subgroups of >20 adolescents (gender or sex, minority status, functional limitations, first language, area of residence) is predictor of subjective or parent-reported need for treatment, likelihood of actually receiving therapy, or type, content or success of treatment, or other factors above.
Other correlates of adolescent outcome include caretaker-reported family characteristics and correlations between adolescent and caretaker ratings for symptoms and functionality. Finally, we will evaluate whether therapist characteristics (sociodemographics, training, experience, specific skills, subjective competence (TCPR), and having an IPC-A therapist training or supervision, or implementation support (NoMAD, PRESS) are outcome predictors, independent from adolescent characteristics.
Analysis of pathways to care
We will describe the proportion of adolescents who receive any support for depression and who receive IPC-A, as well as time to treatment or support (Kaplan-Meyer analysis).
We will characterize the schools and municipalities of recruitment based on the number of professionals overall, and therapists trained and providing IPC-A in relation to the number of adolescents at the school or municipality. This information will be used to evaluate the impact of availability of IPC-A therapists on likelihood of equally receiving any treatment for depressive symptoms, time to therapy/TAU treatment, and outcome of depressed adolescents recruited to the study (Hypothesis 1). Combining different evaluations, we will the estimate utility and added value of implementation of IPC-A.
Economic evaluations of IPC-A
The overall goal of the economic evaluation of IPC-A is to estimate costs and cost-effectiveness of the IPC-A intervention to provide information for health and social care decision-makers. Our aim is to evaluate whether the IPC-A is cost-effective as compared to TAU and no intervention in a 6- and 12-month follow-up from a societal perspective. Also, we aim to evaluate the IPC-A intervention’s effect on health and societal care service use and costs of adolescents with depressive symptoms in 2-, 5-, and 10-year follow-ups compared to TAU and no treatment. The cost-effectiveness of the IPC-A intervention will be evaluated together with the effectiveness study at 12 months and therefore the study design will be as described previously. We will use the effectiveness data and registers of health and social care services and medical purchases collected as described above.
The cost-effectiveness evaluations will combine both effectiveness and costs information of the IPC-A as compared to TAU and no treatment. Two separate analyses will be conducted. First, we will use EQ-5D-Y-based QALYs as the effectiveness outcome. Second, we will use PHQ-9-A scores as the effectiveness outcome. We will apply the limited societal cost perspective including, for instance, intervention costs with relevant use of both health and social care services and medicine purchases from national registers. To enable the use of micro-costing, we will collect the resource uses from multiple sources and use National unit costs for health and social care services in monetarization [70]. Multiple imputations [81] will be performed for missing effectiveness outcomes and cost items if needed.
We will use standard methods of cost-effectiveness analyses, and will, for instance, apply incremental analysis of the effects and costs. First, we will assess dominance of the intervention, that is, whether an intervention is more effective and less costly. In case without clear dominance, we will calculate incremental net health benefit or net monetary benefit comparing the alternatives with 95% confidence intervals [82].
Data management
Data entry: Data will be collected using the THL in-house questionnaire engine Lomakepalvelu (questionnaire service).
Data coding: All participants will receive automatically generated identifiers and additional, automatically generated identifiers for caretakers and professionals. All survey data will be stored using this research ID. Register data including person IDs will be managed using the Findata Kapseli service. Sensitive personal information will be stored separately from any questionnaire data. All other data will be stored pseudonymized.
Data storage: Data will be stored on the THL database system OLAP server, where the survey data, sample data, and register data will be collected for analysis. Participant identifier data will be stored separately on the THL research and scheduling service “Tutkimus ja ajanvarauspalvelu TAP”.
Data confidentiality: Subjects have no access to information provided from other linked persons. Data access is restricted by user roles with permission of PI. No access to participant level data is provided.
Data monitoring committee will be comprised of the senior researchers in the team (Linnaranta, Marttunen, Ranta, Lammintakanen, Heinonen, Lahti, Koskinen, Karvonen, Kaltiala, Oksanen) and will monitor the number of participants every three months (adolescents with subsequent depression who received IPC-A, TAU or no treatment, caretakers and professionals) and missing data. They will make the final decision about finishing recruitment or changing procedures to enrich recruitment for any group to reach sufficient power to respond to the research questions. If necessary, these modifications will be reported to the ethics committee and in scientific reports. Additionally, the same committee will audit data collection procedures every 6 months. No independent auditing committee is nominated since the treatment is not under control of researchers.
Dissemination policy
The local results will be communicated to school and healthcare professionals annually. The research team includes several important national and regional stakeholders, and the main results will be disseminated into clinical and national development of health services in real time. The public will be informed through media interviews and other forms of communication.
Authorship eligibility guidelines
We will follow international and journal guidelines for authorship eligibility.