Background
The prevalence of mental disorders in young people is the highest of any age group [
1], with the onset of high prevalence disorders such as depression, anxiety and substance use peaking within the age range of 18 to 24 years [
2]. There are many negative consequences, both immediate and long-term, associated with mental disorders, including impairments in social functioning, poor education and employment attainment and achievement [
3‐
5], and increased risks of self-harm and suicide [
6]. These outcomes do not solely occur in people with full-threshold or severe forms of disorder; considerable impairment in functioning is associated with what are often referred to as 'sub-threshold' mental health problems, which are equally, if not more, prevalent [
4,
7,
8].
Despite the prevalence and adverse outcomes of experiencing mental health problems during adolescence and young adulthood, young people are often reluctant to seek help for mental health problems [
9] and are the least likely of all age groups to receive appropriate mental health care [
1,
10]. To better facilitate the engagement of young clients, services need to be youth-friendly, delivered in a low-stigma setting and offer accessible and acceptable interventions for young people [
11,
12] that are developmentally appropriate [
13,
14]. Effective treatments for this population that target early phases or sub-threshold levels of disorder have the potential to reduce the risk of persistence and recurrence [
3,
15,
16], and impairments in social, educational and vocational functioning [
3‐
5].
A potentially useful framework to guide treatment decision-making is the clinical staging model for psychiatric disorders, which proposes matching specific interventions to specific stages of illness [
17‐
19]. This model is predicated on the notion that treatments delivered earlier in the course of illness development will be safer and more effective than those delivered later in the course of more established illness, with earlier treatment potentially preventing progression to more severe forms of disorder [
17]. For example, milder, yet potentially serious disorders at a sub-threshold or early stage may respond to simple interventions such as psychosocial support, self-help strategies and psycho-education, reserving more intensive psychotherapy and/or pharmacotherapy for later or more severe stages of illness. However, the majority of studies that have contributed to the current evidence base of interventions for young people with depression and anxiety have included participants with full-threshold levels of disorders (e.g., see [
20‐
22] for systematic reviews). It remains unknown whether less complex or intensive interventions, often used as control conditions in treatment studies of more severe disorders, would be feasible and effective treatments for those experiencing milder or sub-threshold forms of mental health problems.
The majority of psychological treatment trials for young people with depression and/or anxiety disorders have used cognitive-behaviour therapy (CBT), or adaptations of this therapy, as the intervention [
20,
21]. These trials have typically included participants with moderate to severe full-threshold disorders of prolonged duration, typified by the two major studies of psychological and pharmacological therapies for depression; the Treatment for Adolescent Depression (TADS; [
23]) and the Adolescent Depression Antidepressant and Psychotherapy Trial (ADAPT; [
24]). Brief forms of this therapy have rarely been offered, with 12 sessions as standard [
20] and most trials have been based in specialist mental health settings, making it unclear whether the intervention would be feasible or acceptable for young people with mild to moderate or sub-threshold forms of disorders who present for treatment in primary or enhanced primary care settings.
The multiple strategies in the mode of CBT disseminated in the TADS study has been criticised as being too dense, with simpler models of CBT that focus on one or two core components, such as behaviour activation and problem solving, argued to be more beneficial [
25]. Indeed, a recent meta-analysis of psychotherapy for depressed children and adolescents demonstrated that both cognitive (i.e., CBT) and 'non-cognitive' (for example, behavioural activation, family therapy, behavioural problem solving, group support and social skills training) strategies were equally effective in treating depression [
21], suggesting that the specific targeting of cognitions might not be a necessary component of effective treatment in young people [
26]. Further, it has been argued that young people appear to be more interested in treatment that offers them a chance to be listened to and to learn new skills rather than develop a deeper understanding of the psychological processes that contribute to their behaviour [
27]. Combined, these findings suggest the importance of exploring alternative psychotherapies to CBT that may be more acceptable and effective in younger populations with mild to moderate or sub-threshold levels of disorder.
Given the concerns raised with the necessity of targeting cognitive distortions in young people and the difficulties in disseminating CBT, we were interested in exploring psychological interventions that were less complex and could be delivered in a shorter number of sessions. It was also of interest to explore interventions that have the potential to be delivered in primary care settings, which may be more appropriate settings for young people with sub-threshold or mild to moderate high prevalence disorders. Furthermore, an overarching criticism of interventions for young people with depression and anxiety symptoms is that health risk behaviours that co-occur with mental health problems tend to be overlooked [
26]. These health risk behaviours include substance use, eating problems and low levels of regular physical activity. Interventions that can incorporate behavioural activation, such as problem solving therapy [
28‐
30] and exercise interventions [
31], are beginning to be explored as potentially effective interventions in reducing depression and anxiety symptoms in young people.
Problem solving therapy (PST) aims to assist a person in learning to cope more effectively with their current difficulties, as well as developing skills that can be used in other settings and times in their life [
32]. PST aims to achieve this by systematically generating solutions to current problems and implementing a structured plan to resolve the difficulties, thereby introducing new behaviours and skills to effectively solve everyday problems [
33]. The therapy focuses on how to implement changes in the 'here and now' rather than working through the meaning and impact of past experiences [
33,
34]. Given the relationship between stressful life events and the early onset of depression [
35], PST has face validity as an intervention among young people. To date, its effectiveness has been evaluated in two studies in this age group. In 2008, Eskin and colleagues [
29] randomly assigned 46 self-referred high school or university students (mean age 19 years) who met DSM-IV criteria [
36] for major depressive disorder to either PST (n = 27) or a wait-list control group (n = 19). At the end of treatment, the 6 individual sessions of PST were more effective than a wait-list control in reducing depression symptoms and suicidal ideation, as well as increasing assertiveness and self-esteem in this sample. These changes were maintained at a 12-month follow-up assessment. Arguably, changes in these constructs can assist young people in negotiating and responding to future challenges through the development of relevant skills. Participants allocated to the PST intervention attended all 6 sessions of the treatment, indicating that it is an acceptable form of treatment for young people with depression and suicidal ideation. However, the use of a wait-list control group may be an inadequate comparison. It has been criticised because it only allows for the control of the passage of time, but not for other potential non-specific therapeutic factors, such as supportive contact [
37].
In an earlier and smaller trial by Lerner and Clum (1990), group-based PST (n = 9) was compared with supportive psychotherapy (n = 9) in young people (mean age 19 years) who had suicidal ideation and self-reported depressive symptoms, recruited through the psychology department of a university [
30]. The design had an appropriate condition to control for non-specific therapeutic effects and each intervention consisted of 10 group sessions over a period of 5-7 weeks. PST was more effective than supportive therapy in reducing depressive symptoms and hopelessness, but suicidal ideation decreased by a similar amount in both treatment groups. Combined, these studies provide a preliminary evidence-base for using PST as an intervention with younger populations, in particular young people with depressive symptoms. Although Lerner and Clum's study contained 10 sessions, compared with the 6 used by Eskin and colleagues, the duration of the interventions were shorter than the average duration of CBT (see [
20]). This is consistent with a recent meta-analysis of psychotherapy for depression in young people showing no correlation between treatment duration and outcome, indicating that briefer treatments may have a similar effect to those of longer duration [
21].
As mentioned above, health risk behaviours, including low levels of physical activity, tend to be overlooked in psychological interventions with young people, although both mental health and physical health benefits have been found [
26]. Exercise interventions for those with psychological difficulties are proposed to improve mood by interrupting or distracting the person from dysfunctional or negative thoughts and by the release of endorphins via strenuous exercise [
38]. Weekly monitoring of physical activity within psychotherapy sessions has been found to be effective in reducing depression and anxiety symptoms [
39]. A key component of the success of exercise interventions appears to be the encouragement and assistance provided to participants to engage in regular physical activity, as well as benefits derived from assessment and routine monitoring of daily levels of exercise (e.g., see [
40]).
Although based on a small number of trials of variable quality, a systematic review of exercise interventions in predominantly healthy children and young people found positive short-term effects on self-esteem, with no reported adverse effects [
41]. A more recent systematic review of exercise in the prevention and treatment of depression and anxiety in children and young people [
31] found a small effect in favour of exercise, however, again, the number of included trials was small and their quality variable. Whether the exercise interventions were of high or low intensity made little difference to the outcomes. The evidence base for the effectiveness of exercise interventions in children and young people who are experiencing mental health problems is scarce as the majority of trials have been conducted in healthy populations. Further high-quality studies are required to evaluate whether exercise is an effective treatment for depression and anxiety in young people, particularly those with emerging symptomatology.
As noted above, it is essential to include an active control group when designing a treatment trial in order to control for placebo or expectancy effects, or for the non-specific effects of a therapeutic relationship [
21]. We believe this is also warranted when conducting studies in clinical help-seeking populations. Control groups with comparable intensity and duration of exposure to the active treatment are essential in order to conclude that the therapy is effective over and above the non-specific therapeutic effects of compassion, attention, empathic listening and support [
37,
42]. Therefore, in psychotherapy trials, control groups that offer a comparative amount of supportive personal contact are superior to the use of a wait-list control [
37]. Supportive counselling (SC) has often been used as a control condition in psychotherapy trials in adult populations as a control for non-specific relationships effects by offering non-directive, emotional support through the establishment of a therapeutic alliance based on empathic listening [
43,
44]. There has been only one reported RCT in adolescents with major depressive disorder receiving either CBT, family therapy or SC [
45]. CBT was the superior treatment in the shorter-term outcome of symptom reduction, however, the long-term outcomes over two years showed no differences between the groups with regard to recovery, recurrence or level of functioning, with the majority of participants recovering during this time-frame [
45]. Both the National Institute for Health and Clinical Excellence (NICE) guidelines [
46] and the American Academy for Child and Adolescent Psychiatry practice parameter [
47] for treating children and adolescents with depression recommend that those with mild or brief depression initially be offered psychoeducation and supportive counselling. As demonstrated in an RCT of antidepressant medication and routine specialist care with and without CBT (the ADAPT study [
24]), a substantial proportion (21%) of child and adolescent participants with moderate to severe major depression responded to a brief intervention that was offered prior to randomisation that included psychoeducation and mental state monitoring, provided within an empathic and supportive framework. As such, SC has face validity as a suitable control condition for young people in the early stages of mild to moderate depressive disorders.
In summary, there is emerging evidence to suggest that PST and exercise interventions may have benefits in reducing symptoms of mental distress, particularly depression, in younger populations, although there is a need for further research that utilises adequate control conditions. It is also of interest to explore the effects of less complex or intense interventions separately and whether there are additional benefits gained from delivering the interventions together.
Authors' contributions
AGP, SEH, AFJ, ARY, PDMcG and RP, conceived of the study, and along with AM and BM, participated in its design. AGP, SEH and RP drafted the manuscript, with input from the remaining authors. All authors have read and approved the final manuscript.