The results were divided into three main sections: (1) experiences with user involvement, reported through studies using qualitative research methods; (2) effectiveness of user involvement, reported through studies using quantitative research methods; and (3) safety associated with user involvement, reported in either qualitative or quantitative studies. First, search results, sources, characteristics, and quality assessment of the included articles are reported.
Literature search results
A total of 4,978 titles were identified through 11 databases and other sources, and 31 articles were included in the systematic review. Most articles were excluded during the screening of titles and abstracts, leaving 229 articles for full-text assessment. Consensus on inclusion/exclusion was reached for all except two articles, where a majority vote was used to make a final decision. Adolescent co-researchers were consulted for six articles where there were initial discrepancies in researchers’ assessments. Further details with reasons for inclusion and exclusion of articles are provided in the PRISMA flow diagram (Fig. 1).
Sources of included articles
Most included articles (n = 26) were identified through database searches, but six were only found using other sources (Table 3). No single database identified more than 12 included articles, and half of the included titles were only found through a single source. Four articles were suggested by some of the 22 researchers in the field of user involvement in adolescents’ mental healthcare we contacted, and two titles that were found by searching reference lists of included articles.
Characteristics of qualitative studies
Twenty-four studies reporting on qualitative data were included, with a total of 587 participants (median 22, IQR 15–30) (Table 4). The majority of participants were adolescents (n = 491, 84%), whereas the remaining were parents, guardians or care providers (n = 64, 11%), and healthcare staff (n = 32, 6%), reporting on adolescent involvement. Although there was considerable variation in adolescents’ gender distribution between studies (female range 20%–100%), the overall proportion of females and males was equal. Studies were carried out within a wide range of primary and secondary healthcare services (details in Table 4). Most studies (n = 15) included either adolescents with specified diagnosed mental health conditions, such as depression, eating disorders, and ADHD; or adolescents with self-reported mental health problems including self-harm, suicidal thoughts or behaviours, and drug or alcohol problems. Mental health problems were not specified in the remaining nine studies. User involvement at the individual level was reported in 17 studies and at the organizational level in 11 studies (four at both levels).
Quality assessment of qualitative studies
All studies satisfied the first two criteria of the Critical Appraisal Skills Programme (CASP) guidelines , including a clear aim of the research and the appropriateness of using qualitative methodology to address the research goal (Table 5). The CASP guidelines suggest that it is then worth proceeding with an assessment of the remaining questions.
Overall, most studies (n = 14) were of moderate quality, one-third were of high quality, and two studies were of low quality. The most common weakness in the studies was a lack of consideration or reporting of the relationship between the researchers and the participants, which was only adequately done and sufficiently described in four studies. Other prevalent limitations included a lack of rigour in reporting of data analysis methods (n = 8), participant recruitment strategies (n = 7), and consideration of ethical issues (n = 7). A complete overview of CASP questions and criteria may be found in Appendix 2.
Characteristics of quantitative studies
Seven studies used quantitative methods, out of which six reported on user involvement at the individual level [33,34,35,36,37,38], and one at the organizational level . This included a single randomized controlled trial ; a non-randomized comparative study ; two longitudinal prospective cohort studies [33, 34]; a cohort study using pre- to post-assessment ; and two cross-sectional surveys [35, 39], out of which one also used repeated measures for some participants . There was considerable heterogeneity between studies. Further study characteristics are presented in Table 6.
Quality assessment of quantitative studies
The six studies reporting on user involvement at the individual level were all considered to have a high risk of bias, according to the Cochrane Collaboration’s guidelines . The study assessing user involvement at the organizational level included two types of psychometric tests as part of assessing an outcome measure . Three of the studies were, according to assessments carried out using the PRECIS tool , considered to be more pragmatic than explanatory [36,37,38]; and the remaining three were equally pragmatic and explanatory [33,34,35]. Further details are presented in Table 6.
Experiences with user involvement
Thematic syntheses were carried out separately for user involvement at the individual and at the organizational level. Each theme is described and references to the research literature are provided.
User involvement at the individual level
The thematic synthesis of qualitative studies reporting on user involvement at the individual level resulted in three themes reported below: unilateral clinician control versus collaborative relationship; capacity and support for active involvement; and the right to be involved.
Unilateral clinician control versus collaborative relationship
Adolescents’ involvement could be described as a dichotomy between unilateral control and collaborative relationship. Although a continuum of involvement could be envisaged, most study participants’ descriptions suggested that clinical practice involved either health personnel being in control of adolescents’ treatment and clinical decision-making, or adolescents becoming extensively involved in their own treatment and shared decision-making processes.
Health personnel’s unilateral control was found in several studies where adolescents described lack of control with limited possibilities to voice their opinion, limited treatment choices and limited involvement in decision-making processes [40,41,42,43,44,45,46,47]. Adolescents reported that health personnel exerted pressure and made decisions. This was illustrated by adolescents reporting that they did not feel heard [40, 42], feeling left out from meetings, being interrupted, ignored or not asked for their opinions; and pressured or forced to comply with health personnel’s decisions to attend meeting sessions, engage in uninteresting activities and to take medication [40, 43,44,45,46,47]. A perception of unilateral control could also result from receiving too little information about their health and treatment [42, 45]. Adolescents were reluctant to voice their opinions as they were only encouraged to express their views when they were consistent with health personnel’s perspectives and expressed in what was perceived to be an acceptable manner and at an appropriate time [40, 42]. Unilateral control could result when adolescents felt activities were not individually adapted, which prevented their participation . Some health personnel were sceptical of the idea of handing over control to adolescents, whereas others were opposed to controlling and enforcing compliance of their young patients .
Other health personnel and adolescents described a collaborative therapeutic relationship throughout the entire treatment process [43, 48]. Collaborative relationships provided a framework that facilitated adolescents’ involvement. Key features of the framework included a good adolescent–practitioner relationship, open communication, and shared decision-making processes. As part of a collaborative relationship, health personnel offered adolescents context-appropriate choices, and regularly checked to what extent they wanted to be involved in decision-making processes. A good practitioner–adolescent relationship was essential as part of building trust [43,44,45, 49] and was characterized by open communication where health personnel shared their knowledge as professionals, as well as carefully listened to adolescents’ own experiences [42, 49, 50]. Adolescents could share their experiences with the use of medication and other aspects, which could help provide treatment options that were suitable for the individual adolescent . Other examples of active collaboration included adolescents choosing their case manager, opting in or out of group participation, and engaging in various forms of treatment. The collaborative relationship, which included adolescents being offered choices in matters that affected their health care , contributed to shared decision-making processes [42,43,44,45, 49,50,51,52].
A collaborative relationship contributed to adolescents becoming more actively engaged in their treatment. The opposite, being left out of meetings, interrupted, ignored or not asked for input , or that health personnel exerted pressure and made unilateral decisions, contributed to distress and reducing their willingness to be involved in their treatment [40, 42,43,44,45, 47]. Not being involved in implementation of plans contributed to passive compliance and disengagement from the therapeutic process . In a collaborative relationship where trust was established and adolescents received sufficient information, adolescents’ active participation in their therapy was facilitated [42,43,44,45, 49, 50, 54]. Adolescents’ involvement was associated with higher treatment attendance rates  and continuation of treatment; as opposed to treatment drop-out [44, 54]. Receiving enough information and support was associated with identifying treatment goals, self-care activities, and areas of decisional conflict ; practising ways to share information with health personnel ; and making informed choices for their healthcare .
Capacity and support for active involvement
Across all study participants, capacity and support were experienced as key to adolescents’ involvement with different experiences and nuances conveyed among them. Capacity was described through adolescents’ ability to be involved and share their personal experiences, whereas health personnel’s capacity was described through available time and professional knowledge. Furthermore, practical or social support could strengthen adolescents’ involvement [45, 49, 50, 54,55,56].
The different studies provided conflicting evidence between and within adolescents themselves, caregivers, and healthcare staff on adolescents’ capacity to be actively involved in their healthcare [42, 43, 49, 53, 57]. Some health personnel considered adolescents’ young age, immaturity, symptoms or diagnoses, and lack of interest, to be potential barriers to involving them in their treatment and care in general, and in decision-making processes in particular [42, 43]. Moreover, other health personnel thought it was challenging to judge adolescents’ level of understanding due to medication effects . Some suggested adolescents were not interested in attending and contributing to meetings , or were too depressed or lethargic to be actively involved in their treatment . Contrary to these views, other health personnel  and adolescents themselves [53, 57] said they were interested in and motivated to be involved in decisions affecting their treatment. They wanted to be heard, and they had clear ideas about their care and the capacity to make sound judgements about it.
Health personnel’s capacity was questioned by adolescents. They reported that staff members were overwhelmed by their workload, thereby serving as a barrier to involvement of adolescents in their care [45, 57]. Adolescents’ involvement in treatment decision-making depended on the information they were provided by health personnel, which in turn was dependent on their professional competence about for example medication options, expected outcomes, side-effects and possible treatment choices .
Being informed about their health and treatment options was a typical form of practical support for adolescents’ active involvement [45, 49, 50, 54]. Too little information resulted in adolescents feeling lack of support through insufficient control and lack of motivation to be involved in their treatment [42, 45]. In order for information to be of help, it had to be relevant to adolescents . Practical support could also involve enabling adolescents to come to consultations and limited transport options could reduce their possibilities to be more actively involved in appointments and activities . However, adolescents also needed social support, for example by being heard, offered context-appropriate choices, and encouraged to actively participate in decision-making processes [43, 45, 49, 50, 54].
Although several studies suggested that adolescents wanted to be actively involved in decision-making processes, adolescents also expressed awareness of the challenges associated with being in a transitional phase, moving from childhood to adult life . They sought support from others as part of the process, in particular by seeking information and guidance from parents and health personnel to help them make decisions [42, 49, 50, 52, 54]. According to adolescents, their parents and health personnel could support adolescents by sharing their professional knowledge and to provide them with tools such as shared decision worksheets , to help them make choices for their healthcare . Adolescents were of the opinion that through a thorough exploration of their experiences, relationships, support networks, and views, health personnel would be in a better position to provide treatment options that were acceptable to adolescents and compatible with their cultural background [51, 52]. Health personnel could for example combine this with their professional knowledge to suggest treatment options other than medication .
The right to be involved
A prerequisite for adolescents’ involvement in their treatment was a basic understanding of their inherent right to be involved [41,42,43, 49, 50, 53, 57]. Regardless of their age, adolescents wanted to be heard, their autonomy to be respected, and to be involved in decisions affecting their treatment, health, and wellbeing [41, 43, 48, 49, 53, 54, 57]. Although the degree of need for involvement varied between adolescents, they actively sought opportunities to be involved in decision-making processes , and expressed a wish to maintain some control through involvement in the patient–practitioner relationship . They considered this to be essential to maintain their sense of autonomy [42, 49, 54]. Involvement could include for example decisions about their treatment plans [41, 43]; choice and change of therapist [43, 48, 54]; the time, length and frequency of treatment sessions [48, 54] and text message feedback solutions to express such wishes ; which family members who could attend meetings ; and the right to refuse health personnel’s proposals , including the use of medication . Health personnel mostly shared adolescents’ views of their fundamental right to express their opinion, and they considered it a helpful contribution to treatment, although some healthcare personnel were sceptical about giving adolescents control of decisions related to their treatment [42, 43].
User involvement at the organizational level
The thematic synthesis of qualitative studies reporting on user involvement at the organizational level resulted in two themes reported below: involvement outcomes relevant to adolescents’ needs; and conditions for optimal involvement.
Involvement outcomes relevant to adolescents’ needs
Involving adolescents at the organizational level should contribute to outcomes relevant to adolescents’ needs, seen from the perspectives of adolescents, caregivers, and health personnel. In general, participants expressed that adolescents’ involvement contributed to developing and improving mental health services or that it had the potential to do so [40, 56, 59,60,61,62,63]. More specifically, this included the development and use of terminology and models for mental health and participation relevant to adolescents [56, 59, 62]. The design and contents of interventions and psychoeducational resources should reflect adolescents’ experiences and needs . Allowing adolescents the opportunity to influence the design and implementation of treatment programmes and interventions to improve treatment outcomes helped strengthen the relevance, appropriateness, and acceptability of the treatment [60,61,62,63]. Adolescents’ involvement did also contribute to change the treatment environment so that it was better adapted to adolescents’ needs, for example to make conference rooms less formal . Adolescents’ perspectives did also contribute to improve the content of health personnel’s training, and the relevance and quality of the services .
Adolescent consultants contributed to empower other adolescents with mental health challenges to take charge of their recovery through, e.g. educational or one-on-one support. They helped other adolescents and parents to identify their goals, self-care activities, and areas of decisional conflict , as well as to negotiate the patient–practitioner relationship when adolescents did not get along with their counsellor . Implications for adolescents who participated as consultants could potentially also support their sense of autonomy and self-efficacy and empower them to take charge of their own recovery. Moreover, they could gain work experience, build professional and social skills, and expand their networks within the context of a safe environment with proper support [55, 59].
Conditions for optimal involvement
Conditions for adolescents’ optimal involvement at the organizational level reported across study participants included openness to adolescents’ viewpoints and understandings, clarity of roles, information provision, autonomy, skills training, backgrounds and personal experiences, diversity, and formal recognition of efforts to involve adolescents [45, 50, 53, 55, 56, 59, 61, 63].
In order to involve adolescents at the organizational level, professionals needed to be open to adolescents’ viewpoints and understandings of mental health , and clear definition and clarity of roles should be agreed and described to understand the boundaries and limitations of adolescents’ involvement [50, 59, 61].
Adolescents also thought involvement could be optimized by information provided for them about existing services and projects which they could be involved in [45, 50]. By being given the freedom to identify and make decisions about projects they cared about and could run themselves [45, 50, 56, 61], adolescents could make autonomous decisions about whether and the extent to which they wanted to be involved .
Skills training supported optimal involvement of adolescents at the organizational level. Such training could introduce roles, tools, and methods for shared decision-making processes [50, 59]. Tools could for example include methods to formalize and facilitate shared decision-making while still allowing flexibility for the individual needs of adolescents and parents .
Adolescents having personal experiences with the mental health services could optimize their involvement at the organizational level, particularly if they worked directly with other adolescents as peer consultants, so that they could better understand their concerns and needs [59, 61]. Adolescents who had received hospital treatment for serious mental illnesses had clear ideas concerning rules, regulations, and treatment and could make sound judgments about such treatment . Furthermore, adolescents with diverse backgrounds and those from “disadvantaged” backgrounds would strengthen the diversity in perspectives and increase the likelihood that changes to services would be relevant to adolescents of, e.g. ethnic minority backgrounds [55, 59].
Formal recognition of adolescents’ contribution as consultants was to provide payment as employees rather than involving them as volunteers, and to enable them to work both independently and be involved in group activities . Adolescents pointed out that leaders could recognize staff who encouraged user involvement, organized workshops, and discussed their experiences, as well as communicate the benefits of user involvement within their clinics .
Effectiveness of user involvement
A narrative report of results of individual studies on the effectiveness of user involvement is presented in text and in tabular form (Table 6). The articles reporting on individual studies are presented according to the level of evidence associated with their research design (from randomized controlled trials to cross-sectional surveys). No synthesis of data is presented due to heterogeneity of interventions and outcomes.
User involvement at the individual level
Out of six identified articles, three assessed the effectiveness of additional support to facilitate adolescents’ involvement in their own care [36,37,38]; one assessed the effectiveness of shared decision-making on adolescents’ ability to handle mental health problems in the short term  and their overall strengths, difficulties and self-confidence in the longer term ; and one reported the prevalence of adolescents’ participation in decision-making .
The results of a randomized controlled trial suggest that additional support provided by a team working with adolescents with severe mental health problems, their family and social support network in developing a care plan, may increase youth participation in treatment planning, both in the short (3–4 weeks) and longer term (10–12 weeks) (p < 0.01) . These adolescents were more than twice as likely to positively rate care planning meetings, compared to those in the control group (p < 0.001).
A non-randomized controlled study that took place in a youth mental health service clinic found a significant effect, measured using the Shared Decision-Making Questionnaire (SDMQ-9) (p = 0.015), of a combination of peer workers engaged with adolescents at intake assessment together with an online shared decision-making tool prior to counselling sessions, compared to a historical comparison group . The results did, however, only suggest a small clinical effect.
Results of a cohort study suggested that adolescents who had higher expectations but poorer experiences of shared decisions-making in psychosocial care had lower degrees of understanding of and ability to handle mental health problems at 3 months, compared to adolescents whose experiences corresponded with their expectations (OR 4.2, 95% CI 1.7–10.8, p < 0.01) . In the long-term follow-up at one year, shared decision-making was associated with significant changes in adolescents’ Total Difficulties Score (TDS), measured using the Strengths and Difficulties Questionnaire (SDQ) . Although results were then irrespective of adolescents’ expectations, improvement in self-confidence was lower when communication needs were not met (p < 0.001).
An online aid aimed at supporting adolescents with mild to severe depression in making decisions in line with their values and preferences, as well as in line with the existing research evidence, was tested in a cohort study from baseline to eight weeks . At 8 weeks, results showed a statistically significant reduction in depression (PHQ-9) scores, although the clinical importance of this was uncertain (mean change 2.7 points, 95% CI, 1.3;4.0). Significant improvements were also found on the Decisional Conflict Scale (DCS) from before to after use of the decision aid (mean change 17.8 points, 95% CI 13.3;22.9).
Results of a cross-sectional survey suggested that over half of adolescents who had been hospitalized for mental health conditions felt they were able to participate in decision-making processes, whereas one quarter felt they could participate partially and one quarter not at all .
User involvement at the organizational level
A cross-sectional and repeated measures survey reported on results of testing a Youth Empowerment Scale–Mental Health (YES-MH) for adolescents with various mental health difficulties . The survey measured adolescents’ participation in team-based services and treatment planning for mental health services. Results of a factor analysis suggested empowerment of adolescents through their confidence and capacity to work with service providers to select and optimize services; to help providers improve services; and to help other youth with mental health difficulties.
Safety associated with user involvement
No study aimed to report on the safety associated with user involvement in adolescents’ mental healthcare. A few studies did however report on issues that potentially could influence the safety of adolescents’ mental healthcare. Examples included a qualitative study where involvement of adolescents in decision-making was thought to be a potential threat to their safety by some health personnel . Their arguments did, however, not pertain to the individual youths’ capability or competence to participate in decision-making, but could be understood as exercising undue professional power as they considered adolescents not to be competent in making decisions for their mental healthcare irrespective of their arguments, state of health or level of maturity. In a second qualitative study, some staff expressed concerns about risks associated with involvement of adolescent consultants. For example, the experience of being a consultant was thought by some staff to potentially be overwhelming to adolescents and could serve as a barrier to their own recovery . Healthcare personnel thought these adolescents could also misunderstand conversations between staff and thereby breach confidentiality.