Systematic review of school-based prevention and early intervention programs for depression

Journal of Adolescence 33 (2010) 429–438

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Systematic review of school-based prevention and early intervention programs for depression Alison L. Calear*, Helen Christensen Centre for Mental Health Research, Building 63, Eggleston Road, The Australian National University, Canberra, ACT 0200, Australia

a b s t r a c t Keywords: Review Depression School-based Child Adolescent

A systematic review was conducted to identify and describe school-based prevention and early intervention programs for depression and to evaluate their effectiveness in reducing depressive symptoms. Forty-two randomised controlled trials, relating to 28 individual school-based programs, were identified through the Cochrane Library, PsycInfo and PubMed databases. A large proportion of the programs identified were based on cognitive behavioural therapy (CBT), and delivered by a mental health professional or graduate student over 8–12 sessions. Indicated programs, which targeted students exhibiting elevated levels of depression, were found to be the most effective, with effect sizes for all programs ranging from 0.21 to 1.40. Teacher program leaders and the employment of attention control conditions were associated with fewer significant effects. Further schoolbased research is required that involves the use of attention controls, long-term follow-ups and which focuses on the training and evaluation of sustainable program leaders, such as teachers. Ó 2009 The Association for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Unipolar depressive disorders often begin in adolescence, with approximately 21–28% of adolescents experiencing an episode of major depression by the age of 19 years (Hankin et al., 1998; Lewinsohn, Rohde, & Seeley, 1998). In any one year, the prevalence of depressive disorders amongst this population can range from 1% to 8% (Costello, Mustillo, Erkanli, Keeler, & Angold, 2003; Costello et al., 2002). These figures however, may be an under estimate of the true nature of emotional difficulties in the community, with many children and adolescents exhibiting elevated, but subclinical, levels of depressive symptoms (Bayer & Sanson, 2003; Gotlib, Lewinsohn, & Seeley, 1995). Depression is one of the major causes of morbidity among adolescents, with the disorder often taking a chronic, recurrent, and episodic course (Merry, McDowell, Wild, Bir, & Cunliffe, 2004). Some of the negative outcomes associated with adolescent depression include poor academic performance, family and social dysfunction, physical ill health, suicide attempts and completed suicide (McGorry, Purcell, Hickie, & Jorm, 2007; Merry, McDowell, Wild, et al., 2004). These difficulties are also often evident in children and adolescent with subclinical levels of depression (Gillham, 2003; Gotlib et al., 1995), and can continue into adulthood where further occupational, economic and interpersonal difficulties can arise (Bayer & Sanson, 2003; Cicchetti & Toth, 1998). Given the high prevalence rate and associated negative effects, the need to prevent the development of depressive disorders has become essential. One means of achieving this goal has been the implementation of prevention programs in schools. Schools are viewed as an ideal environment in which to present prevention programs, as they have unparalleled contact with youth and thus represent a place in which the majority can be reached (Masia-Warner, Nangle, & Hansen, 2006).

* Corresponding author. Tel.: þ61 2 6125 8406; fax: þ61 2 6125 0733. E-mail address: [email protected] (A.L. Calear). 0140-1971/$ – see front matter Ó 2009 The Association for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.adolescence.2009.07.004

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A.L. Calear, H. Christensen / Journal of Adolescence 33 (2010) 429–438

The inclusion of mental health programs in schools also allows the emotional problems of previously unidentified and untreated youth to be addressed (Ginsburg & Drake, 2002). Some of the common barriers to traditional mental health services can also be reduced in the school environment, such as stigma, cost, time and location (Barrett & Pahl, 2006; Masia-Warner et al., 2006). Three types of prevention programs, universal, indicated and selective, have been utilised in schools to prevent depressive symptoms (Mrazek & Haggerty, 1994). Universal programs are delivered to all students regardless of symptom level and are often designed to build resiliency or enhance general mental health (Barrett & Turner, 2004). Selective programs target children and adolescents who are at risk of developing a depressive disorder by virtue of particular risk factors such as parental depression or divorce, while indicated programs target individuals with mild or early symptoms of depression (Mrazek & Haggerty, 1994). In some cases, participants of universal programs who have elevated symptoms of depression are excluded from analyses, so as to establish true preventative effects. Although there are a number of benefits associated with selective and indicated programs, school administrators often prefer universal interventions (Horowitz, Garber, Ciesla, Young, & Mufson, 2007). This preference likely stems from the broad application of universal programs and the reduced stigma and time associated with them, as the screening of participants is not necessary (Horowitz et al., 2007; Offord, Chmura Kraemer, Kazdin, Jensen, & Harrington, 1998). Both efficacy and effectiveness trials have been conducted in the school setting. Efficacy trials assess an intervention under optimal and controlled conditions, while effectiveness trials evaluate a program under naturalistic or real-world conditions that approximate usual care (Dane & Schneider, 1998; Flay et al., 2005). A number of reviews have been undertaken to explore the efficacy of depression prevention programs for children and adolescents (Horowitz & Garber, 2006; Merry, McDowell, Hetrick, Bir, & Muller, 2004; Merry & Spence, 2007; Spence & Shortt, 2007), although no reviews identified to date have specifically focused on all programs presented in schools. An exclusive review of all school-based programs is needed, as the school environment is promoted as an ideal setting for the implementation of prevention programs and the comparability of community and school-based programs is questionable due to differences in the targeted populations and conditions. The current review therefore aims to identify and describe school-based prevention and early intervention programs for depression, and their effectiveness in reducing symptoms of depression. In addition, the review attempts to identify the factors that are likely to predict significant outcomes. Relevant variables that were considered include the (a) type of intervention, (b) personnel implementing the intervention, (c) type of intervention content, and (d) type of control condition. Method Search and screening procedures The Cochrane Library, PsycInfo and PubMed databases were electronically searched between 1998 and March 2008, with the key search terms ‘‘school* OR school-based OR adolescent* OR child* OR youth’’, ‘‘prevent* OR early intervent*’’, ‘‘depress* OR mood’’, and ‘‘control*’’. The titles and abstracts of the articles identified by these searches were screened to determine their relevance to the review. Completely irrelevant articles were excluded at this stage, while relevant studies and reviews were retained and the full-text article examined. Studies identified in review articles were also collected and included in the current review. The inclusion criteria for the current review were that (a) study participants were children aged 5–12 years or adolescents aged 13–19 years, (b) the primary aim was to reduce or prevent the symptoms of depression, or to build resilience, (c) the intervention was school-based (delivered as part of the school curriculum or as an after school endorsed activity targeted at school children), (d) a primary outcome measure was depressive symptomatology or diagnosis, (e) the study used randomised controlled trial (RCT) methodology, and (f) the study was published in a peer-reviewed, English language journal. Studies that fulfilled the inclusion criteria were coded, with all relevant data extracted and recorded.

Effect size calculations To compare the efficacy and effectiveness of the prevention and early intervention programs identified, standardised effect size (ES) estimates were calculated using Cohen’s d (Cohen, 1988) or phi (Castellanos & Conrod, 2006). Positive standardised effect size estimates indicate that the intervention group improved more than the control group. All reported effect sizes were calculated using Cohen’s d, unless otherwise specified. In some cases an effect size could not be calculated as the necessary data was not reported. The statistical significance of the difference in depressive symptom scores between the intervention and control group is also reported, based on the statistical tests reported in the individual papers. A formal meta-analysis was not undertaken because of poor quality ratings, the relatively small number of trials and the inability to accurately compare efficacy and effectiveness trials. Effectiveness trials involving classroom teachers have been found to produce smaller effects than efficacy trials conducted with mental health professionals or research staff (Gillham et al., 2006). As the majority (85%) of the effectiveness trials were universal, a bias could be created if the combined effects of universal and indicated programs were directly compared.

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Quality ratings Study quality was also assessed using a validated measure that assesses quality against three key criteria: randomisation, double-blinding, and withdrawals and dropouts (Jadad et al., 1996). One point is allocated to a study if it involves the randomisation of participants, while a second point is awarded if the specific details of the randomisation process are described, such as the use of a random number table. Two additional points are awarded if a study is double-blinded and the doubleblinding process is adequately implemented and described. A final point is awarded to studies that report trial withdrawals and dropouts and specify the reasons for each of these. Quality ratings can range from 0 to 5, although intervention trials of school-based mental health programs, which often cannot achieve double-blind conditions, rarely receive scores above 3. Quality ratings were calculated, as poor quality intervention studies can overestimate the size of intervention effects (Moher et al., 1998). Results Forty-two RCTs, relating to 28 school-based prevention and early intervention programs for depression, were identified in the current review. Table 1 presents the efficacy or effectiveness data for each program, as well as the quality ratings and program details for each trial.

Program target population Of the 42 studies identified, 23 (55%) were universal trials that included all students, three (7%) were universal trials that excluded students exhibiting clinical levels of depression, 10 (24%) were indicated trials, and six (14%) were selective trials. The six selective trials were targeted towards parental divorce (CSG), ethnicity (PRP), behavioural problems (PRP and WEI), and personality specific cognitive distortions (PTCBI). Adolescents were the target audience for just over half of the trials identified (57%; 24 studies). Eleven (46%) of the trials involving adolescents reported a significant reduction in symptoms of depression (d ¼ 0.31–1.40, median ¼ 0.60, n ¼ 10), while six (54%) of the trials delivered to children reduced depression (d ¼ 0.48–1.05, median ¼ 0.64, n ¼ 5).

Program content Cognitive Behavioural Therapy (CBT), or components of it, formed the basis of the majority of programs (76%). Other common therapeutic approaches employed included psychoeducation (17%) and interpersonal therapy (IPT; 9%). Of the studies that delivered CBT, 18 (56%) reported a significant reduction in depressive symptoms (d ¼ 0.21–1.40, median ¼ 0.51, n ¼ 16). Seven (50%) of the studies that delivered a non CBT-based therapeutic technique significantly reduced depression scores (d ¼ 0.31–1.35, median ¼ 0.48, n ¼ 5). Of the seven effective trials, three included psychoeducation (d ¼ 0.31–1.35, median ¼ 0.40, n ¼ 3) and three included IPT (d ¼ 0.31–1.35, n ¼ 2).

Program leader A number of programs (33%) had multiple program leaders and were categorised according to the description provided by the author of the research paper. Program leaders tended to be graduate students (40%), mental health professionals (36%), and school teachers (31%). Members of the research team (17%), nurses (5%) and paraprofessionals (2%) also fulfilled this role in a small number of trials. Six (46%) of the trials that utilised a teacher as the program leader reported a significant reduction in depression (d ¼ 0.33–0.52, median ¼ 0.39, n ¼ 5), compared to 18 (58%) of the trials that employed another type of program leader (d ¼ 0.21–1.40, median ¼ 0.60, n ¼ 18).

Program sessions The length of programs ranged from two sessions to being year-long, with the majority of programs implemented over eight to 12 sessions. Nineteen (62%) of the trials that evaluated a program consisting of eight to 12 sessions reported a significant reduction in depressive symptoms (d ¼ 0.21–1.35, median ¼ 0.52, n ¼ 17), while four (36%) trials evaluating programs less than eight sessions or greater than 12 sessions also reported significant effects (d ¼ 0.35–1.40, median ¼ 0.59, n ¼ 4). Session length was also quite variable, with just under three quarters of the program sessions running between 40 and 50 minutes (31%, 13 studies) and 60–90 minutes (45%, 19 studies). Three of the programs (CSG, FRIENDS, and PRP) included parent information sessions, which ranged from four to six sessions and complemented the school-based program. The FRIENDS program also included two booster sessions, which were presented one and three months after the completion of the main program.

Program

Trial citation

Universal programs AMT Hains (1992) CWSC Horowitz et al. (2007) IPT-AST Horowitz et al. (2007) LARS & LISA Po¨ssel, Seemann, and Hautzinger (2008) LISA-T Po¨ssel, Horn, Groen, and Hautzinger (2004)

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Table 1 School-based prevention and early intervention programs for depression. Sample (age)

Control group

Program content

Program leader

No. sessions

Post-test effect size

Follow-up effect size (months)

Quality rating 1 3 3 2 2 3 1 2 1 1 2 2

Adolescent Adolescent Adolescent Adolescent Adolescent

(15–16 (14–15 (14–15 (13–14 (13–14

years) years) years) years) years)

16 281 268 301 347

WL NI NI NI NI

Relaxation CBT þ Psychoed. IPT þ Psychoed. CBT CBT

Grad. þ researcher Grad. Grad. Grad. þ MHP Grad. þ MHP

9 8 8 10 10

1.13a 0.40a 0.31a 0.03 0.49

Sheffield et al. (2006) Shochet and Ham (2004) Hains and Szyjakowski (1990) Hains (1992) Hains and Ellmann (1994) Bonhauser et al. (2005) Clarke, Hawkins, Murphy, and Sheeber (1993): study 1 Clarke et al. (1993): study 2 Ruini, Belaise, Brombin, Caffo, and Fava (2006) Chaplin et al. (2006) Lowry-Webster et al. (2001, 2003) Lock and Barrett (2003) and Barrett et al. (2006) Barrett, Lock, and Farrell (2005) Barrett and Turner (2001)

Adolescent Adolescent Adolescent Adolescent Adolescent Adolescent Adolescent

(14–15 (13–14 (16–17 (15–16 (NR) (15–16 (NR)

years) years) years) years)

1045 2664 21 17 21 198 513

NI NI WL WL WL NI NI

CBT CBT þ IPT CBT CBT CBT Exercise Psychoed.

Teacher Teacher Researcher Grad. þ researcher Grad. þ MHP Teacher Teacher

8 11 9 9 13 Year-long 3

0.04 NAa 0.18 0.93a 1.40a,b NA 0.19

_d 0.12 (6) 0.03 (6) 0.06 (6) 0.42 (3) 0.48 (6) 0.05 (12) NAa (12) _d _d _d _d 0.05 (3)

Adolescent (NR) Adolescent (NR)

300 111

NI AC

BT þ Psychoed. WBT

Teacher MHP

5 4

0.06 0.24

0.27 (3) _d

2 2

Adolescent þ child (11–14 years) Adolescent þ child (10–13 years) Adolescent þ child (9–16 years)

208 594 737

NI WL WL

CBT CBT CBT

MHP þ teacher Teacher MHP

12 10 þ 2 booster 10 þ 2 booster

0.52a 0.30a,b 0.15

3 2 2

Adolescent þ child (9–16 years) Child (10–12 years)

693 489

NI NI

CBT CBT

Grad. þ MHP MHP þ teacher

10 þ 2 booster 10 þ 2 booster

PPP

Pattison and Lynd-Stevenson (2001)

Child (9–12 years)

66

AC þ NI

CBT

MHP

10

Child (NR)

335

NI

Psychoed.

Grad. þ MHP

16

PTP

Petersen, Leffert, Graham, Alwin, and Ding (1997) Rooney et al. (2006)

AC ¼ 0.52 (8) NI ¼ 0.73 (8) NA (6, 12)

1

PSAS

NA MHP ¼ 0.09 T ¼ 0.54a AC ¼ 0.09 NI ¼ 0.11 NA

NA (12) 0.33a (12) 0.21a (12) NA (24, 36) NA (12) _d

Child (8–9 years)

136

NI

CBT

MHP

8

0.56a

AO

Quayle et al. (2001)

Child (11–12 years)

47

NI

CBT

Grad.

8

0.40

Adolescent þ child (11–14 years)

463

AC

CBT

Grad. þ teacher

12

0.14

Adolescent þ child (11–14 years)

466

NI

CBT

Grad. þ teacher

12

0.14

Adolescent (12–14 years)

1500

NI

CBT

Teacher

8

0.36a

PSFL RAP SIT

– – – – PRP FRIENDS

Universal programs (clinical diagnoses excluded) PRP Gillham et al. (2007)

PSFL

Spence, Sheffield, and Donovan (2003, 2005)

years)

2 2

2

0.25 (9) 0.06 (18) 0.66a (6)

2

0.07 (6) 0.16 (12) 0.11 (18) 0.27a (24) 0.31a (30) 0.37a (36) 0.18 (6) 0.40a (12) 0.35a (18) 0.51a (24) 0.48a (30) 0.24 (36) 0.06 (12) 0.03 (24) 0.10 (36) 0.05 (48)

3

2

2

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N

RAP-Kiwi

Adolescent (13–15 years)

392

AC

CBT þ IPT

Teacher

11

0.02

0.12 (6) 0.07 (12) 0.05 (18)

3

Indicated programs ACE Sheffield et al. (2006) AO Roberts et al. (2003, 2004)

Adolescent (14–15 years) Adolescent (11–13 years)

629 189

NI NI

CBT CBT

Teacher MHP

8 12

0.16 0.05

3 2

BG

Stice et al. (2006)

Adolescent (15–22 years)

117

WL

CBT

Grad.

4

0.71a

CWSC

Clarke et al. (1995)

Adolescent (14–16 years)

172

NI

CT

MHP

15

0.35a

10

a

0.05 (12) 0.07 (6) 0.12 (18) 0.14 (30) 0.40a (1) 0.13 (6) 0.07 (6) 0.01 (12) 0.96a (3) 1.00a (6) 0.50a (6) 0.31 (12) _d

2

IPT-AST

Merry, McDowell, Wild, et al. (2004)

Young et al. (2006)

Adolescent (11–16 years)

41

NI

IPT þ Psychoed.

Grad. þ researcher

1.35

a

2 2 3

Puskar et al. (2003)

Adolescent (14–16 years)

89

NI

CBT

Nurse

10

0.48

–

Adolescent (14–19 years)

41

NI

CBT

Nurse

8

NA

POP

Lamb, Puskar, Sereika, and Corcoran (1998) Yu and Seligman (2002): study 3

Adolescent þ child (8–15 years)

220

NI

CBT

Teacher

10

0.25a

PRP

Gillham et al. (2006)

Adolescent þ child (NR)

44

NI

CBT

Researcher

8

0.09

PASCET

Weisz et al. (1997)

Child (NR)

48

NI

CBT

Grad.

8

0.57a

0.33a 0.39a 0.64a 0.46a 0.64a

Child (NR) Child (8 years)

56 127

NI NI

CBT SS

NR PP

12 24

NAa 0.48a

NAa (6–36) _d

1 1

Child (NR)

48

NI

CBT

Grad. þ researcher

12

1.01a

2

2

Selective program (conduct/behavioural problems) PRP Cutuli et al. (2006) WEI King and Kirschenbaum (1990) Selective program (ethnicity/low income) PRP Cardemil et al. (2002, 2007): study 1 (Latino)

(3) (6) (6) (12) (9)

2

2 2

Cardemil et al. (2002, 2007): study 2 (Af. Am.) Selective program (parental divorce) CSG Stolberg and Mahler (1994)

Child (NR)

103

NI

CBT

Grad. þ researcher

12

0.16

0.79a (3) 1.05a(6) 0.65a (12) 0.61a (24) NA (3, 6, 12, 24)

Child (NR)

129

NI

CBT

Grad. þ MHP

14

NA

0.02 (12)

1

Selective program (personality) PTCBI Castellanos and Conrod (2006)

Adolescent (13–16 years)

423

NI

CBT þ Psychoed.

MHP

2

0.16c

_d

2

A.L. Calear, H. Christensen / Journal of Adolescence 33 (2010) 429–438

2

TKC

Note. ACE ¼ Adolescents Coping with Emotions, AMT ¼ Anxiety Management Training, AO ¼ Aussie Optimism, BG ¼ Blues Group, CSG ¼ Children’s Support Group, CWSC ¼ Coping with Stress Course, IPTAST ¼ Interpersonal Psychotherapy-Adolescent Skills Training, POP ¼ Penn Optimism Program, PPP ¼ Penn Prevention Program, PRP ¼ Penn Resiliency Program, PSAS ¼ Penn State Adolescent Study, PTCBI ¼ Personality-Target Cognitive-Behavioural Intervention, PTP ¼ Positive Thinking Program, PASCET ¼ Primary and Secondary Control Enhancement Training, PSFL ¼ Problem Solving for Life, RAP ¼ Resourceful Adolescent Program, RAP-Kiwi ¼ Resourceful Adolescent Program – New Zealand version, SIT ¼ Stress Inoculation Training, TKC ¼ Teaching Kids to Cope, WEI ¼ Wisconsin Early Intervention, – ¼ no program name. Af. Am. ¼ African American. AC ¼ attention control, WL ¼ wait-list control, NI ¼ no intervention control. BT ¼ Behaviour Therapy, CBT ¼ Cognitive Behavioural Therapy, CT ¼ Cognitive Therapy, IPT ¼ Interpersonal Therapy, Psychoed. ¼ psychoeducation, SS ¼ Social Skills, WBT ¼ Well-Being Therapy. Grad ¼ graduate student/intern, MHP ¼ mental health professional, PP ¼ paraprofessional, T ¼ teacher. NA ¼ effect size not able to be calculated, NR ¼ value not reported. a Significant difference in depression scores between intervention and control groups. b Elevated anxiety group only. c phi estimate of effect size. d Post-test comparison only.

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Evaluation control group Thirty-three (79%) of the trials identified in the current review utilised a no intervention or usual care control group, while the remaining seven (17%) and four (9%) trials employed a wait-list or attention control group respectively. Participants in the no intervention, usual care, and wait-list control conditions tended to continue usual classes during the intervention phase, while students in the attention control group undertook a structured program that did not contain the elements of the intervention being evaluated. Of the four trials that included an attention control condition, only one (25%) reported significantly lowering participants’ depressive symptoms (d ¼ 0.37), while 23 (58%) of the trials utilising a wait-list, no intervention or usual care control condition reported reductions in depression (d ¼ 0.21–1.40, median ¼ 0.52, n ¼ 21). Evaluation sample size, randomisation, and follow-up Participant numbers in each trial varied considerably, ranging from 16 to 2664, with the median number of participants being 194. The process of randomisation differed between trials, with 24 trials (57%) randomly allocating individuals to the intervention and control condition and 12 trials (29%) randomising by school and six (14%) by class. Of the studies identified, 10 (24%) did not collect any comparison data past post-test, while 20 (48%) studies had a follow-up period of 12 months or longer and seven trials (17%) had measurements of at least two years. Evaluation outcome measures and study quality A number of depressive symptom measurement scales were employed in the trials reviewed, with the three most commonly used scales being the Children’s Depression Inventory (CDI; 48%), the Center for Epidemiological Studies Depression scale (CES-D; 19%), and the Reynolds Adolescent Depression Scale (RADS; 14%). Other measurement scales included the Beck Depression Inventory (BDI) and the Hospital Anxiety Depression Scale (HADS). Study quality ranged from one to three, with 26 (62%) studies receiving a rating of two. Of the remaining studies, eight (19%) obtained a rating of one and eight (19%) received a rating of three. Overall symptom outcomes Overall, 23 of the 42 (55%) identified trials significantly reduced participants’ depressive symptoms at post-test or followup, with effect sizes ranging from 0.21 to 1.40. The effect sizes of the 19 trials that did not obtain significant results ranged from 0.54 to 0.73. Nineteen of the 23 (83%) positive trials reported significant effects (d ¼ 0.25–1.40) at post-test, while the remaining four studies recorded significant differences solely at follow-up (d ¼ 0.21–0.66). Thirty-two (76%) trials collected follow-up data, of which 13 (41%) reported significant effects (d ¼ 0.21–1.05) and 19 did not (d ¼ 0.12 to 0.73). Indicated program outcomes The trials were also examined as a function of their broad type. Six of the 10 (60%) indicated trials exhibited significant differences between the intervention and control conditions at post-test (d ¼ 0.25–1.35), while four studies failed to find a significant difference (d ¼ 0.05–0.16). Nine of the ten (90%) indicated trials included a follow-up measurement period, of which six (67%) reported significant effects (d ¼ 0.33–1.00) and three failed to find a difference (d ¼ 0.12 to 0.14). Five of the 10 (50%) indicated trials exhibited significant differences at both post-test and follow-up (Puskar, Sereika, & Tusaie-Mumford, 2003; Stice, Burton, Bearman, & Rohde, 2006; Weisz, Thurber, Sweeney, Proffitt, & LeGagnoux, 1997; Young, Mufson, & Davies, 2006; Yu & Seligman, 2002). Universal program outcomes Of the 23 universal trials that included all participants regardless of symptom level, nine trials (39%) showed reductions in depressive symptoms at post-test (d ¼ 0.30–1.40), while 14 trials did not (d ¼ 0.54 to 0.49). Sixteen of the 23 (70%) universal trials measured differences at follow-up, with four (25%) of the trials finding significant effects (d ¼ 0.21–0.66) and 12 not (d ¼ 0.05 to 0.73). Two of the 23 (9%) universal trials reported significant effects at both post-test and follow-up (LowryWebster, Barrett, & Dadds, 2001; Lowry-Webster, Barrett, & Lock, 2003; Shochet & Ham, 2004). Only one of the three (33%) universal trials that excluded participants with clinical levels of depression was successful in reducing participants’ levels of depression at post-test (d ¼ 0.36), while the remaining two trials failed to find a difference (d ¼ 0.02–0.14). All three studies collected follow-up data, of which one (33%) reported significant effects (d ¼ 0.27–0.51), and two did not (d ¼ 0.12 to 0.10). None of the trials reported significant differences at post-test and follow-up. Selective program outcomes Three of the six (50%) selective trials (behavioural problems and ethnicity) exhibited significant differences at post-test (d ¼ 0.48–1.01), while three failed to find a significant difference (d ¼ 0.16; phi ¼ 0.16). Of the six selective trials, four (67%)

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included a follow-up period, of which two (50%; behavioural problems and ethnicity) found significant differences between the intervention and control conditions (d ¼ 0.61–1.05) and two did not (d ¼ 0.02). Two of the six (33%) selective programs exhibited reductions in depressive symptoms at post-test and follow-up (Cardemil, Reivich, Beevers, Seligman, & James, 2007 [study 1]; Cardemil, Reivich, & Seligman, 2002 [study 1]; Cutuli, Chaplin, Gillham, Reivich, & Seligman, 2006).

Discussion Overall the results of this review are mixed, with only half of the trials identified reporting a significant reduction in depressive symptoms at post-test or follow-up. Small (0.21) to large (1.40) effect sizes were reported for these trials. A number of factors appeared to influence these outcomes, including the intervention structure (indicated vs. universal), program leader (teacher vs. other), and control condition (attention control vs. other). Indicated programs appeared to be more efficacious than selective and universal programs, with a higher proportion of successful trials at post-test and follow-up, and more consistent outcomes at both post-test and follow-up, supporting the use of indicated programs to produce immediate and long-lasting change. This finding reflects previous research, which suggests that indicated programs may be more efficacious than universal interventions due to the increased room for change amongst participants with elevated symptoms of depression (Offord et al., 1998; Reivich, Gillham, Chaplin, & Seligman, 2005). The universal programs that included all participants regardless of symptom level, displayed the lowest level of efficacy and effectiveness. These findings could lead one to devalue the use of universal depression programs in schools relative to the use of indicated programs. This conclusion may be too hasty however, as some universal programs have been found to be effective and thus it may be the quality of the universal programs being implemented that are not producing the significant effects, rather than the universal delivery style itself. The focus therefore, should maybe not be on comparing the effectiveness of indicated and universal programs, as there is evidence to suggest the potential of both, but rather focus on the programs being utilised and what it is about their content and delivery style that make them more or less effective. Further research into the components of consistently effective programs would help to disentangle the potential influences of these factors. Over two thirds of the trials in the current review utilised mental health professionals, graduates or researchers as program leaders. Program leaders such as these are costly, and the number required to roll-out a program would exceed the number available to fulfil the role. Programs are likely to be more sustainable when they use classroom teachers, or appropriately trained school staff such as guidance counsellors. The results of the present review found that a smaller percentage of trials involving teacher program leaders were successful in reducing symptoms of depression, than trials involving other program leaders. This finding suggests that programs are more effective in the hands of mental health professionals or the program developers, and that there is a need to establish whether the specific training of classroom teachers can lead to improved outcomes. The median effect size of the trials employing teacher program leaders was somewhat smaller than those studies employing other program leaders. This finding is in line with previous research that has found effectiveness trials utilising teacher program leaders to produce smaller effects (Gillham et al., 2006) than efficacy trials involving mental health professionals or program developers. Future research should focus on ways to improve the implementation of these programs by classroom teachers through increased specialist training and the provision of appropriate support materials. The majority of studies identified in the current review employed a no intervention or usual care control group, with very few studies utilising an attention control group, although this is clearly a better design to evaluate the specific effects of a program (Gillham, Shatte´, & Reivich, 2001). The current review found that trials using an attention control condition were associated with a lower median effect size (0.37 vs. 0.52) and were somewhat less likely than other control condition trials to find a significant effect. This finding suggests that the absence of an attention control may inflate intervention effects. Further research is needed with a larger number of trials involving an attention control to ascertain the extent of attention effects. A larger proportion (62% vs. 36%) of the trials evaluating an intervention program consisting of eight to 12 sessions were successful in reducing depressive symptoms, than trials assessing programs that were longer than 12 sessions or shorter than eight. This suggests that overly short and long programs may be less successful in reducing depressive symptoms, possibly due to an insufficient exposure to the program material, or too much information to absorb and apply. Some of the other program factors, that did not necessarily influence effects, provided some interesting results. For instance, the majority of the trials reviewed employed a prevention or early intervention program based on the principles of CBT. The propensity to employ CBT techniques is not unexpected, with much research supporting CBT as the treatment of choice for depression in children and adolescents (Compton et al., 2004). According to Compton et al. (2004) medium to large effects can be obtained in treatment trials comparing CBT interventions for depression with wait-list, inactive or active controls. The preventative CBT programs reviewed here produce a median effect size of 0.51 and thus are in line with previous treatment findings, although treatment trials may be of a higher quality and be more likely to be compared to an attention placebo control. Not all of the studies employing CBT techniques significantly reduced symptoms of depression however, raising the possibility that other factors, such as the program’s innovation and capacity for engagement, rather than the underlying therapeutic technique, may contribute to outcomes. If this is the case, then program developers should look closely at the delivery styles of consistently effective programs, such as the Penn Resiliency Program, to identify the elements of the program that are engaging and producing the desired effects. The assessment of participant knowledge following the

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completion of a program, such as a measure of CBT literacy, and an analysis of its relationship to treatment outcomes would help identify best practice programs. The importance of long-term follow-up measurements was reflected in the results of the current review, with a number of studies (Barrett, Farrell, Ollendick, & Dadds, 2006; Gillham et al., 2006, 2007; Quayle, Dziurawiec, Roberts, Kane, & Ebsworthy, 2001) not detecting significant differences until the follow-up period. A study conducted by Gillham et al. (2007) is a classic example of this, in that significant effects were not reported until 12 months’ post-intervention and continued for up to 36 months. According to Gillham et al. (2001), participants often need to pass through a period of elevated risk for preventative effects to emerge and this might take some time. Without long-term follow-ups potential effects could be missed and the effectiveness of school-based programs underestimated. Long-term follow-ups are also essential in determining the duration of effects, and the period at which booster sessions may be beneficial (Gillham et al., 2001). Future studies therefore should include follow-up assessments to ensure all effects are detected. The self-report measures employed by the trials in the current review were commonly used, reliable and valid measures of depressive symptoms. Ten of the trials also employed diagnostic interviews in assessing depression, although in four of the trials interviews were conducted only for participants with elevated symptoms. Diagnostic interviews can contribute considerably to a prevention trial by providing clinical outcome data, but are expensive and take time to administer. Selfreport symptom measures are considered to be acceptable measures of intervention effects in school-based prevention trials. Many experts consider self-report measures to be as important as clinical diagnoses, as the two are often interrelated and associated with the same deficits and dysfunction (Gillham et al., 2001; Gotlib et al., 1995; Horowitz et al., 2007). Trial quality was on the whole quite poor, with only eight of the 42 studies receiving a rating of three, and thus the results of this review should be interpreted with this in mind. The low quality scores tended to stem from a failure to report the details of the randomisation process and an inability to achieve double-blind standards. It is unlikely therefore that the poor quality ratings impacted results, as they were often linked to inadequate trial reports, rather than poor trial designs. Future trial reports should specifically disclose the process of randomisation, including details of the generation of random number sequences. Four (33%) of the 12 trials that randomised schools to each condition analysed the data using a method that accounted for the clustering of students within schools. A fifth study initially analysed its data according to the clustered design but then reverted to univariate analyses after determining that only a small proportion of the total variance was accounted for at the school level, while a sixth trial acknowledged the need to analyse the data in light of the nested design but was unable to do so due to a lack of statistical power. With the clustering of students within schools having the potential to affect results, future evaluations of school-based prevention programs in schools should be encouraged to consider the impact of clustering on results. Overall the current findings provide some support for the implementation of depression prevention and early intervention programs in schools. Indicated approaches appear to produce the strongest results, with small to moderate reductions in depression at post-test and follow-up. Universal and selective trials have also produced positive effects. Trials utilising attention controls and teacher program leaders produced smaller and fewer significant effects. Future school-based research should focus on producing higher quality studies, which include teacher program leaders and training, attention controls, and measures of adherence and engagement. Evaluations of the cost-effectiveness of depression prevention and early intervention programs should also be undertaken, as they are sorely lacking in the prevention literature. Such analyses would assist in the long-term funding and implementation of prevention programs in schools.

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