The Depression Prevention Initiative: Trauma as a Moderator of Prevention Outcomes

Abstract

Interpersonal Psychotherapy-Adolescent Skills Training (IPT-AST) is an evidence-based indicated depression prevention program that has been shown to reduce depression symptoms. Research is needed to identify moderators of IPT-AST’s effects. Although trauma history has emerged as a moderator of depression treatment outcomes, the impact of trauma on short- and long-term outcomes in the context of preventive interventions for adolescent depression is unknown. This study examines the impact of trauma on prevention outcomes in a school-based randomized controlled trial (RCT) in which 186 adolescents (mean age = 14.01 years, SD = 1.22; 67% female) were randomly assigned to IPT-AST delivered by research staff or to group counseling (GC) provided by school counselors. Trauma history significantly moderated intervention outcomes during the active phase of the intervention but not during long-term follow-up. During the active phase, youth in IPT-AST with low or no trauma exposure experienced significantly greater reductions in depression symptoms than youth in GC with low or no trauma exposure, but there were no significant differences in rates of change between the two interventions for youth with high or any trauma exposure. These findings highlight the importance of assessing trauma and investigating whether these interventions can be tailored or supplemented to enhance the effects for youth with trauma exposure.

Keywords

adolescent(s)depression evidence-based interventions school-based mental health services treatment outcomes

Depression is a prevalent and debilitating disorder (World Health Organization, 2017). Although research has demonstrated the efficacy of a number of depression treatments, evidence suggests that existing treatments are only able to reduce about 30% of the burden of depression due to the disorder’s high incidence and barriers to timely access to treatment (Andrews et al., 2000; Chisholm et al., 2004). Therefore, there is growing recognition that depression prevention programs are needed to reduce the incidence of depression and associated burden (Munoz et al., 2010).

Adolescence represents a vulnerable developmental period for depression; depressive symptoms increase, and one in five adolescents experience a depressive episode (Hankin et al., 1998; Thapar et al., 2012). Adolescent depression is associated with a host of negative psychosocial consequences lasting into adulthood including unemployment, early pregnancy, suicide attempts, decreased educational achievement, as well as later mood, anxiety, and substance use disorders (Fergusson & Woodward, 2002; Johnson et al., 2018). As such, adolescence is an opportune time to deliver preventive interventions, and a number of depression prevention programs have been developed and studied in universal, selected, and indicated samples (Hetrick et al., 2016).

One such prevention program is Interpersonal Psychotherapy-Adolescent Skills Training (IPT-AST). IPT-AST is an indicated group preventive intervention for adolescents with elevated depressive symptoms that targets interpersonal issues related to the onset of depression in adolescence. To date, IPT-AST has shown promising results in several studies. Compared with usual school counseling, IPT-AST has been shown to have a greater effect on depressive symptoms, depression diagnoses, and anxiety symptoms, as well as school, social, and overall functioning in adolescents up to 1 year postintervention (Young et al., 2006, 2010; Young, Kranzler, et al., 2012; Young, Makover, et al., 2012). Recent meta-analyses of depression prevention interventions report that IPT-AST is one of a few programs with demonstrated long-term effects (Cuijpers et al., 2008; Hetrick et al., 2016). The current study is a secondary analysis of the Depression Prevention Initiative (DPI), a school-based randomized controlled trial (RCT) comparing IPT-AST with group counseling (GC) through 24 months post-intervention. In the short term, youth in the IPT-AST group experienced significantly greater reductions in depressive symptoms and improvements in overall functioning through 6-month follow-up compared with youth in GC (Young et al., 2016). From 6-month to 24-month follow-up, adolescents in GC continued to experience significant improvements in depressive symptoms and maintained improvements in functioning; adolescents in IPT-AST experienced a nonsignificant increase in symptoms and significant decrease in functioning. Across the entire study period (baseline through the 24-month follow-up), both groups showed significant improvements in depressive symptoms and overall functioning, but there were no significant differences in overall rates of change (Young et al., 2019). These findings suggest that IPT-AST may elicit a more timely improvement in symptoms and functioning than GC, but further research is needed to understand and enhance the long-term impact of IPT-AST. Of note, the lack of long-term effects found in DPI is consistent with the larger prevention literature, especially when an active control condition is included (Hetrick et al., 2016).

In addition to evaluating the overall efficacy of depression prevention programs, it is important to investigate moderators of intervention outcomes (i.e., factors that predict differential responses to the intervention). In their strategic plan for research, the National Institute of Mental Health (NIMH) highlighted the need for a personalized approach to prevention in which interventions are matched to individuals’ needs and circumstances (National Institutes of Health, NIMH, 2015). Investigating moderators can reveal for whom interventions work to tailor and/or augment the interventions to ensure optimal benefit for a specific subgroup of individuals (Kraemer et al., 2002). It is equally important to identify subgroups who receive minimal benefit from a given preventive or treatment intervention so that subsequent interventions can be tailored or supplemented to address these specific needs (Garber, 2008). As such, moderator analyses have the potential to elucidate inconsistent or null findings.

One potentially important moderator of intervention outcomes is trauma exposure. This is particularly salient for adolescents, an age group with high rates of trauma exposure (Breslau et al., 1998, 2004). More than half of adults in the Adverse Childhood Experiences (ACEs) study (Felitti et al., 1998) reported experiencing at least one type of ACE and about one third reported exposure to at least two events (Chapman et al., 2004). ACEs include childhood abuse (emotional, physical, and sexual abuse), neglect (physical and emotional neglect), and household challenges (growing up in a household where there was mental illness, substance abuse, violent treatment of mother, parental divorce, or incarceration of a household member).

There is substantial evidence supporting the relationship between early trauma exposure and depression (see Heim & Binder, 2012 for a review). Specifically, trauma history is predictive of earlier onset of depression, as well as greater number of depressive episodes and comorbidities (Bernet & Stein, 1999). Trauma exposure in youth is common and disposes youth to a number of additional negative psychosocial outcomes including an increased risk of internalizing and externalizing symptoms (Finkelhor et al., 2009), psychiatric disorders (McLaughlin et al., 2012), social withdrawal, and poorer academic performance in adolescence (Lansford et al., 2002).

Studies have reported that exposure to multiple traumas, as opposed to a single trauma, places adolescents at particularly high risk for psychopathology, suggesting an additive effect of trauma (Suliman et al., 2009). Secondary analysis of the ACEs study also indicates the strong relationship between the number of ACEs and lifetime depressive disorders in men and women (Chapman et al., 2004). Due to the frequent co-occurrence of childhood traumas (Felitti et al., 1998), many researchers have adopted a cumulative-risk approach, which combines the number of distinct events to create a person’s risk score (Evans et al., 2013). This approach is useful in highlighting the prevalence of childhood traumatic events and identifying youth in need of intervention, as adolescents who have had multiple traumatic experiences have double the risk of depression than adolescents without trauma exposure (Ford et al., 2010).

In light of the research documenting the association between trauma and depression, trauma has been examined as a potential predictor or moderator of treatment outcomes in randomized controlled depression trials. These studies have examined trauma exposure in different ways. Some have used a yes/no dichotomous variable (Asarnow et al., 2009; Barbe et al., 2004; Shirk et al., 2009) to indicate whether or not adolescents experienced any lifetime trauma. Lewis and colleagues (2010) utilized the trauma section of the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS-PL; Kaufman et al., 1997), which asks youth whether they have experienced 11 traumatic events (yes/no), to categorize participants into four groups based on types of traumatic events experienced.

Regardless of the definition of trauma exposure used, there is growing evidence that trauma exposure predicts or moderates outcomes in depression treatment studies (Asarnow et al., 2009; Barbe et al., 2004; Lewis et al., 2010; Shirk et al., 2009). Trauma history predicted treatment response in an open trial of school-based cognitive-behavioral therapy (CBT); youth with trauma exposure were significantly more likely to meet criteria for a depression diagnosis at posttreatment as compared with youth without trauma exposure (Shirk et al., 2009). In a treatment study of adolescents with depression, exposure to sexual abuse moderated response to treatment. The significant benefits of CBT over nondirective supportive therapy (NST) in rates of change in depressive symptoms and rates of diagnoses at posttreatment were not evident in youth who had been exposed to sexual abuse. Furthermore, at 2-year follow-up, adolescents with trauma exposure had a greater likelihood of depressive relapse and psychiatric hospitalization than youth without trauma exposure, regardless of treatment condition (Barbe et al., 2004).

In the Treatment of Resistant Depression in Adolescents (TORDIA) study, adolescents with depression had significantly greater treatment response from combined CBT and medication versus medication alone (Brent et al., 2008). However, secondary analysis of TORDIA revealed a significantly diminished response to combination treatment at the 12th and final week of treatment among youth with a history of trauma (Asarnow et al., 2009). Further analysis of the moderation findings in TORDIA showed that the poorer response to psychotherapy plus pharmacotherapy in youth with depression and trauma exposure was mostly explained by exposure to physical abuse rather than sexual abuse history, baseline symptom severity, comorbidities, or other familial or demographic variables (Shamseddeen et al., 2011). Findings from a secondary analysis of the Treatment for Adolescents with Depression Study (TADS; March et al., 2004) study, which randomized adolescents with depression to CBT, medication, combination treatment, or placebo found that youth with sexual abuse history did not experience the same benefits from CBT alone at the end of the 12-week treatment period that was evident in youth without a trauma history (Lewis et al., 2010). Only one of these treatment studies provides evidence of trauma’s impact beyond posttreatment but trauma was limited to sexual abuse and the focus was on relapse (Barbe et al., 2004); thus long-term examinations of trauma’s influence on depression outcomes are lacking.

Although the evidence is growing that trauma predicts or moderates depression treatment outcomes at posttreatment, the impact of trauma on short-term and long-term outcomes in the context of preventive interventions for adolescent depression is unknown and warrants investigation. This is an important endeavor for future research given the prevalence of youth trauma exposure, the strong relationship between such experiences and depression, and the notable burden of depression (McLaughlin & Sheridan, 2016). This novel study examined the impact of trauma history on depressive symptom outcomes during the active phase of intervention (i.e., pre-intervention to 6-months) and follow-up phase (i.e., 6- to 24-month post-intervention) in an RCT that compared IPT-AST as delivered by research staff with GC provided by school counselors. We hypothesized that trauma exposure would moderate prevention outcomes, such that the significant difference between IPT-AST and GC in rates of change in depression symptoms during the active phase would be diminished among adolescents exposed to trauma. Furthermore, this study examined the impact of trauma on depression symptoms in the long-term follow-up to evaluate whether trauma exposure was related to long-term rates of change in depression symptoms and might explain the lack of continued benefits of IPT-AST over GC.

Method

Participants

This study utilized data from DPI, a school-based longitudinal RCT comparing IPT-AST to group counseling for adolescents with elevated depression symptoms. At the time of consent and assent, the sample was composed of 186 racially and ethnically diverse adolescents in seventh through 10th grades from participating New Jersey public schools. Baseline characteristics of the sample are described in Table 1.

Table 1.

Baseline Demographic Characteristics.

Demographics	GC (n = 91)	IPT-AST (n = 95)	p value
Age, mean (SD)	13.42 (1.18)	13.56 (1.28)	.43
Female (%)	60 (65.9%)	64 (67.4%)	.84
Racial minority (%)	29 (31.9%)	31 (32.6%)	.91
African American (%)	16 (17.6%)	21 (22.1%)	.44
Asian (%)	5 (5.5%)	3 (3.2%)	.49
American Indian (%)	1 (1.1%)	0 (0.0%)	.49
More than one race (%)	7 (7.7%)	7 (7.4%)	.93
Hispanic (%)	36 (39.6%)	35 (36.8%)	.70
White, nonminority, non-Hispanic (%)	36 (39.6%)	35 (36.8%)	.70
Annual income (%)^a
<US$25,000	15 (16.5%)	17 (18.1%)	.77
US$25,000−US$89,999	33 (36.3%)	38 (40.4%)	.57
≥US$90,000	43 (47.3%)	39 (41.5%)	.43

Source. Table adapted from Young et al. (2019).

Note. GC = group counseling; IPT-AST = Interpersonal Psychotherapy-Adolescent Skills Training.

One participant in IPT-AST did not report annual income. Therefore, percentages are calculated out of 94.

Procedures

Recruitment involved a two-stage screening process to identify students with subthreshold depressive symptoms (see Figure 1). Consent forms and letters that described the depression screening process were sent home to families of 9,123 students. After obtaining parental consent and adolescent assent, students completed the Center for Epidemiologic Studies–Depression Scale (CES-D; Radloff, 1977). About one third of the students participated in the screening. Students with an elevated CES-D score (16 or greater), who agreed to participate in the second stage of screening (n = 271), completed the K-SADS-PL (Kaufman et al., 1997) administered by trained evaluators. Eligibility required the presence of at least two subthreshold or threshold depression symptoms, one of which was depressed mood, anhedonia, or irritability. Additional exclusion criteria were: (a) had a current diagnosis of major depression or other psychopathology rendering prevention inappropriate (dysthymia, bipolar disorder, psychosis, substance abuse, or conduct disorder); (b) reported current active suicidal ideation or significant and repeated nonsuicidal self-injury; or (c) had severe cognitive or language impairments.

Figure 1.

Participant flow chart.

One hundred eighty-six eligible adolescents were stratified by sex within each school before a computer-generated random number sequence was used to randomly assign the adolescents to either IPT-AST (n = 95) or GC (n = 91). Interventions were matched on frequency and duration of sessions. All group sessions took place in the schools participating in the study. The current study utilizes data collected at the time of eligibility through 2 years post-intervention (i.e., baseline, mid-intervention, postintervention, and at 6-, 12-, 18-, and 24-month follow-up), which occurred between 2010 and 2015. At each assessment, the adolescents met individually with a trained clinical evaluator, naïve to group assignment, to complete the evaluation. Adolescents received compensation in the form of a US$20 gift card.

Interventions

IPT-AST

IPT-AST is a manualized group depression prevention intervention that emphasizes psychoeducation and interpersonal skill building. A clinical psychologist and a trained clinical psychology graduate student co-led most of the 18 IPT-AST groups, composed of three to seven adolescents. IPT-AST included two individual pre-group sessions, eight weekly group sessions, an individual mid-group session where the parent was invited to participate, and four individual booster sessions in the 6 months following the group. IPT-AST group leaders identified adolescents’ interpersonal goals during the pregroup sessions. Group sessions included psychoeducation about depressive symptoms and the relationship between emotions and interpersonal experiences, introduction to communication strategies (e.g., putting yourself in others’ shoes and being specific), group activities and role-plays to practice implementing these strategies, and guidance on using these interpersonal skills in interactions outside of group. The main goals of IPT-AST are to reduce conflict and increase social support to improve current mood and prevent the development of future depression. Booster sessions were included to review the strategies from group and apply these strategies to current interpersonal stressors. IPT-AST was administered with high fidelity and competency (see Young et al., 2016 for further details about the intervention and fidelity data).

Group counseling

GC was meant to reflect the heterogeneity of groups run in schools while being enhanced to match IPT-AST on frequency and duration of sessions. Before the study, some schools had never conducted groups while others with preexisting group programs had considerably shorter and less frequent group sessions than GC as delivered for the purposes of the study. GC was meant to be an ecologically valid, yet rigorous, control condition that was designed to answer the question of whether IPT-AST imparted benefits above and beyond other group-based programs that could be feasibly delivered in schools. School counselors led 16 GC groups, which included two to eight adolescents. Like IPT-AST, GC consisted of a pre-group session, eight weekly group sessions, a mid-group session, and four booster sessions. Multiple GC groups reported employing evidence-based cognitive behavioral techniques (Young et al., 2016, 2019).

Measures

Depressive symptoms

The CES-D was used to examine depressive symptoms over the past week. Adolescents rated their experience of various depression symptoms on the widely-used, 20-item self-report measure using a scale from 0 (Rarely or none of the time) to 3 (Most or all of the time). A sample item is, “I was bothered by things that usually don’t bother me.” In adolescent samples, the CES-D has been shown to have high internal consistency, reliability, and validity (Roberts et al., 1990). The analyses in the current study focus on change in CES-D scores from baseline through 24-month follow-up (α = .85–.91).

Trauma

The posttraumatic stress disorder (PTSD) portion of the K-SADS-PL (Kaufman et al., 1997) was administered during the eligibility evaluation to assess lifetime trauma exposure. Adolescents responded yes or no on the 11-item measure that asked if they had ever experienced the following: (a) car accident, (b) other accident, (c) fire, (d) witnessed a disaster, (e) witnessed a violent crime, (f) victim of violent crime, (g) confronted with traumatic news, (h) witnessed domestic violence, (i) physical abuse, (j) sexual abuse, or (k) other event. Trauma exposure was operationalized both cumulatively (number of traumatic events) and categorically (any trauma exposure/no trauma exposure).

Data Analysis Plan

We employed a full intent-to-treat analysis in which all randomized participants (n = 186) were included in the analyses regardless of their degree of participation in the study. We implemented a piecewise three-level hierarchical linear model (HLM) to examine differences between the intervention conditions on rates of change in depression symptoms from baseline to 6-month follow-up (active phase) and 6- to 24-month follow-up (follow-up phase). Level 1 models individual scores over time. At Level 2, we used the individual intercept and slope as outcomes dependent on group. At Level 3, we used the group-specific slopes as outcomes to contrast rates of change between IPT-AST and GC. Moderation effects were investigated by including the three-way interaction of trauma by time by intervention. In the analysis examining cumulative trauma as a moderator, the number of traumatic events was standardized to provide meaningful interpretations at the mean and one standard deviation above and below the mean. In this three-level HLM, intervention group was treated as a random effect and school was treated as a fixed effect. Consistent with our prior analyses with DPI data (Young et al., 2016, 2019), income and CES-D scores at screening were included in the model as covariates. Goodness of fit tests indicated that a natural logarithmic transformation of time fit the data significantly better than linear time. This logarithmic transformation accounts for more rapid change early within phase followed by slower change subsequently within phase. In addition, to ensure multivariate normality of the residuals we normalized CES-D scores using a square root transformation. All models were fit using SAS 9.4 (SAS Institute, Inc, 2017).

Results

Preliminary Analyses

Attrition and missing data

Retention rates were high in DPI (93% through 12 months and 87% through 24 months); therefore, missing data were minimal. We performed pattern-mixture models (Hedeker & Gibbons, 1997) to investigate potential effects of missing data. The results indicated that intervention effects were not dependent on missing data patterns.

Baseline differences

As shown in Table 1, the two intervention groups did not differ significantly on depression symptoms or demographic variables as detailed in Young et al. (2016). As shown in Table 2, trauma exposure was common in youth in both GC and IPT-AST and the two groups did not differ significantly on number of traumatic events they had experienced over their lifetime (cumulative trauma), t(184) = −1.11, p = .27, or lifetime trauma exposure (categorical trauma), χ²(1) = 3.63, p = .06. Half of the adolescents reported experiencing at least one traumatic event (n = 39 in GC; n = 54 in IPT-AST). In addition, 19% (n = 36) of the adolescents reported exposure to multiple traumas. The most commonly reported trauma was being confronted with traumatic news. There were no significant sex differences in cumulative trauma exposure, categorical trauma exposure, or depressive symptoms in the overall sample or within each intervention condition (all ps > .05).

Table 2.

Lifetime Rates of Traumatic Event Exposure by Type.

Traumatic Event Types	GC (n = 91)	IPT-AST (n = 95)	Total (n = 186)
Confronted with traumatic news^a	23 (25.56%)	22 (23.40%)	45 (24.2%)
Witness to domestic violence^b	7 (7.69%)	12 (12.77%)	19 (10.2%)
Car accident	5 (5.49%)	9 (9.47)	14 (7.5%)
Other accident	6 (6.59%)	8 (8.42)	14 (7.5%)
Physical abuse^b	6 (6.59%)	7 (7.45%)	13 (7.0%)
Witness of a disaster	3 (3.30%)	8 (8.42%)	11 (5.9%)
Sexual abuse^b	4 (4.40%)	5 (5.32%)	9 (4.8%)
Witness of a violent crime	5 (5.49%)	4 (4.21%)	9 (4.8%)
Victim of violent crime	3 (3.30%)	3 (3.16%)	6 (3.2%)
Other^b	1 (1.10%)	2 (2.13%)	3 (1.6%)
Fire	0 (0.0%)	1 (1.05%)	1 (0.5%)
Any trauma	39 (42.86%)	54 (56.84)	93 (50%)
Single trauma (one event)	21 (23.08%)	36 (37.89%)	57 (30.6%)
Multiple traumas (more than two events)	18 (19.78%)	18 (18.95%)	36 (19.4%)

Note. GC = group counseling; IPT-AST = Interpersonal Psychotherapy-Adolescent Skills Training.

Two participants, one in GC and one in IPT-AST did not report on confronted with traumatic news. Therefore, percentages are calculated out of 90 and 94, respectively. ^bOne participant in IPT-AST did not report on witness domestic violence, physical abuse, sexual abuse, or other. Therefore, percentages are calculated out of 94.

Moderation Analyses

Cumulative trauma

Active phase

Cumulative trauma, defined as the number of traumatic events experienced, moderated intervention outcomes during the active phase of the intervention, F(1, 167) = 4.92, p < .05; the number of traumatic events youth experienced resulted in a differential response to the intervention through 6-month follow-up. To further investigate this moderation effect, cumulative trauma was standardized and we estimated change in depression at values indicating low cumulative trauma (1 SD below the mean), average cumulative trauma (at the mean), and high cumulative trauma (1 SD above the mean). Among youth with low cumulative trauma, those in IPT-AST experienced significantly greater reductions in depression scores than youth in GC (t[167] = 2.95, p < .05). Specifically, youth with low trauma in IPT-AST experienced a 6.85 point reduction in CES-D scores during the active phase, whereas youth with low trauma exposure in GC experienced a smaller, yet still significant, reduction of 2.51 points on the CES-D (see Table 3). Among youth who experienced an average number of cumulative traumatic events, those in IPT-AST experienced marginally significant greater reductions in depression scores than youth in GC (t[167] = 1.90, p = .06). Specifically, youth with average trauma in IPT-AST experienced a 5.87 point reduction in CES-D scores during the active phase, whereas youth with average trauma exposure in GC experienced a smaller, yet still significant, reduction of 2.51 points on the CES-D.

Table 3.

Changes in Depressive Symptoms.

Trauma Exposure	Intervention group	Change estimate	SE	T	p
Categorical trauma
Active phase
No trauma	GC	−2.67	1.31	−2.11	< .05
No trauma	IPT-AST	−7.24	1.46	−5.31	< .01
Any trauma	GC	−5.45	1.51	−3.84	< .01
Any trauma	IPT-AST	−4.80	1.29	−4.00	< .01
Follow-up phase
No trauma	GC	−3.75	1.14	−3.99	< .01
No trauma	IPT-AST	1.76	1.23	1.16	.25
Any trauma	GC	−1.99	1.37	−1.43	.15
Any trauma	IPT-AST	1.09	1.13	−.13	.90
Cumulative trauma
Active phase
Low trauma	GC	−2.51	1.36	−1.97	< .05
Low trauma	IPT-AST	−6.85	1.34	−6.04	< .01
Higher trauma	GC	−5.51	1.49	−4.20	< .01
Higher trauma	IPT-AST	−4.88	1.27	−4.63	< .01
Follow-up phase
Low trauma	GC	−3.83	1.24	−3.70	< .01
Low trauma	IPT-AST	.32	1.24	.27	.79
Higher trauma	GC	−2.51	1.43	1.52	.13
Higher trauma	IPT-AST	2.57	1.22	.62	.53

Note. Active phase = baseline through 6-month follow-up; follow-up phase = 6- to 24-month follow-up; GC = group counseling; IPT-AST = Interpersonal Psychotherapy-Adolescent Skills Training; low trauma = the number of traumatic events experienced is 1 SD below the average; higher trauma = the number of traumatic events experienced is 1 SD above the average.

Although greater improvements in depression symptoms were found in the short term for youth with low and average levels of cumulative trauma exposure in IPT-AST compared with GC, youth with high trauma exposure did not experience this significant benefit of IPT-AST over GC. There was no significant difference in rates of change in depression symptoms between the two interventions for youth with high trauma exposure (1 SD above the mean; t[167] = −.24, p = .81). Among the adolescents with high cumulative trauma exposure, youth in IPT-AST had significant reductions of 4.88 points on the CES-D and those in GC had significant reductions of 5.52 points on the CES-D (see Figure 2). That is, youth with both low and high trauma exposure showed significant reductions in depressive symptoms in both intervention conditions from baseline through 6-month follow-up; however, the significant difference between IPT-AST and GC in rates of change in depression symptoms during the active phase of the intervention diminished among adolescents with high cumulative trauma exposure.

Figure 2.

Cumulative trauma and changes in depression symptoms.

Follow-up phase

During the follow-up phase (6- to 24-month follow-up), cumulative trauma did not significantly moderate intervention outcomes, F(1, 167) = 0.54, p = .46. Specifically, the number of traumatic events that adolescents had experienced did not result in differential rates of change in depression symptoms during long-term follow-up.

Categorical trauma

Active phase

Trauma, defined categorically (any trauma exposure/no trauma exposure), significantly moderated intervention outcomes during the active phase of the intervention, F(1, 167) = 4.40, p < .07, indicating that exposure to any traumatic event produced a differential response to the intervention through 6-month follow-up. To further investigate this significant interaction effect, we compared change in depressive symptoms in youth with no trauma exposure to change in depressive symptoms in youth with any trauma exposure. Among those with no trauma exposure, youth in IPT-AST experienced significantly greater reductions in depression scores than youth in GC (t[167] = 2.65, p < .01). Specifically, youth with no trauma exposure who participated in IPT-AST experienced a 7.24 point reduction in CES-D scores during the active phase, whereas youth with no trauma exposure who participated in GC experienced a smaller, yet still significant, reduction of 2.67 points on the CES-D (see Figure 3). For youth with trauma exposure, there was no significant difference in rates of change in depression symptoms between the two interventions (t[167] = −.33, p = .74). Adolescents with trauma exposure in IPT-AST had significant reductions of 4.80 points on the CES-D, and youth with trauma exposure in GC had significant reductions of 5.45 points on the CES-D.

Figure 3.

Categorical trauma and changes in depression symptoms.

Follow-up phase

During the follow-up phase (6- to 24-month follow-up) categorical trauma (any trauma exposure/no trauma exposure) did not significantly moderate intervention outcomes, F(1, 167) = 3.19, p = .07. That is, the exposure to any traumatic event did not result in a differential response to the interventions through 24-month follow-up.

Discussion

Depression prevention programs are necessary to reduce the significant burden associated with depression (McLaughlin & Sheridan, 2016; Munoz et al., 2010). In addition, it is important to investigate moderators of these prevention programs to better understand for whom a given intervention may or may not work and to potentially explain equivocal findings. Although researchers have identified various moderators of depression treatment programs including prior trauma exposure, to our knowledge there has been no examination of whether trauma moderates outcomes of depression prevention programs. In the current study, we examined whether trauma exposure moderates depressive symptom outcomes in a school-based RCT comparing IPT-AST with GC.

Trauma exposure, defined cumulatively and categorically, moderated short-term rates of change in depression symptoms. Specifically, when examining trauma cumulatively (i.e., number of traumatic events experienced), youth with low trauma exposure had greater reductions in depression symptoms in IPT-AST than in GC during the active phase. However, the rates of change from baseline through 6-month follow-up were not significantly different for adolescents with high trauma exposure across the two intervention conditions. In other words, the benefits of IPT-AST over GC in reducing depression symptoms that were evident among youth with low trauma exposure dissipated among youth with high trauma exposure. When examining trauma categorically (any trauma exposure/no trauma exposure) results were similar to cumulative trauma and consistent with our hypothesis. During the active phase, youth in IPT-AST with no trauma exposure showed significantly greater reductions in depression symptoms compared with youth in GC with no trauma exposure. However, the rates of change in depression symptoms were not significantly different between the two intervention conditions among youth with any trauma exposure. Unlike the active phase, we found no evidence that trauma exposure (defined cumulatively or categorically) moderated rates of change in depressive symptoms across the two intervention conditions during the long-term follow-up (6- to 24-month follow-up). Each of these findings or lack of findings will be discussed further below.

The moderating effect of trauma exposure in the active phase of this prevention study is similar to what has been found in previous studies of CBT for youth depression (Asarnow et al., 2009; Barbe et al., 2004; Lewis et al., 2010; Shirk et al., 2009). Thus, the findings of the current study serve as preliminary evidence that trauma has a similar impact in prevention interventions as seen in depression treatment. Taken together, these findings indicate that adolescents with trauma exposure have diminished responsiveness to evidence-based interventions, including CBT and IPT-AST. Similar to the CBT delivered in the adolescent depression treatment studies (Asarnow et al., 2009; Barbe et al., 2004; Lewis et al., 2010; Shirk et al., 2009), IPT-AST does not specifically target trauma-related topics. IPT-AST was delivered with high fidelity in DPI (Young et al., 2016) and did not allow for adapting session content to address trauma. On the contrary, group content in GC was determined by the school counselors. There may have been more flexibility to specifically address trauma and/or to apply strategies that are relevant to both trauma and mood. It is possible that this flexibility is important in intervening with adolescents with multiple clinical concerns (depressive symptoms and trauma exposure). As noted in earlier papers (Young et al., 2016, 2019), many of the GC counselors utilized evidenced-based techniques, in particular cognitive techniques. Thus, one possible explanation of the similar rates of change between IPT-AST and GC among adolescents with a history of trauma exposure is that GC groups specifically addressed youth trauma, either by the application of evidence-based techniques that are relevant to trauma or through nonspecific factors (e.g., ongoing emotional support), whereas IPT-AST did not.

Another possible explanation for these findings is that there are characteristics of adolescents who have been exposed to trauma that make it difficult for them to benefit from a structured, evidence-based intervention. For example, executive functioning issues and attentional difficulties have been found in youth with exposure to trauma (DePrince et al., 2009). Shirk and colleagues (2014) suggest that the impaired attentional capabilities of youth exposed to trauma may be one explanation for the diminished effects of CBT. It is possible that the techniques emphasized in IPT-AST (e.g., independently monitoring depressive symptoms, altering responses to interpersonal interactions, and promoting the use of new communication skills during emotional interpersonal situations) require attentional and information processing abilities that are compromised in youth exposed to trauma. Although this is possible, it should be noted that the main traumatic event reported by adolescents in the current study was receiving traumatic news. This is distinct from more severe trauma (i.e., abuse), which was a focus in the previous treatment studies (Barbe et al., 2004; Lewis et al., 2010). Our findings suggest that relatively less severe traumatic experiences may result in diminished benefits of evidence-based interventions for depression.

Regardless of the explanation, our findings highlight that, for a subgroup of adolescents with a unique need for intervention (i.e., youth with subthreshold depression symptoms and exposure to trauma), current prevention interventions are falling short. Given the frequent occurrence of traumatic events and the documented link between trauma exposure and depression, we need to determine how to strengthen the effects of prevention programs for this population. Of note, an adaptation of interpersonal psychotherapy (IPT)—from which IPT-AST was developed—focused on PTSD led to a significant decrease in PTSD symptoms for individuals with trauma exposure, especially those with comorbid depression (Markowitz et al., 2015). Some of these adaptations could be incorporated into IPT-AST to increase the applicability and benefits of this program for youth who have been exposed to trauma.

In the long-term follow-up, trauma exposure, defined cumulatively and categorically, did not moderate rates of change in depressive symptoms. As reported in Young et al. (2019), there were significant reductions in depressive symptoms during the follow-up period for youth in GC, whereas youth in IPT-AST experienced a non-significant increase in depressive symptoms. The lack of long-term moderation findings indicates that the rates of change during the follow-up period were similar for youth with and without trauma exposure. Thus, there was no evidence that trauma history explained the lack of long-term benefits of IPT-AST over GC. One consideration is that statistical power was an issue. It is well known that moderation analyses are often underpowered, and it is possible that the present study did not have sufficient power to detect smaller moderation effects during the long-term follow-up when the significant between-group difference dissipated. Given this was the first study to examine whether trauma moderated rates of change in depressive symptoms over long-term follow-up and there was a lack of sustained benefits of IPT-AST over GC during this timeframe, these findings should be interpreted cautiously. More work needs to be done to examine the impact of trauma on long-term depression outcomes in prevention and treatment studies, both at the symptom level and on later depressive episodes.

There are also important conclusions that can be drawn from the within group findings. Adolescents with trauma exposure (defined both cumulatively and categorically) showed significant reductions in depressive symptoms during the active phase (pre-intervention to 6-months post-intervention) in both intervention conditions. This suggests that youth who are at risk for depression due to emerging depressive symptoms and who also have a trauma history still benefit from participating in depression prevention programs. For IPT-AST, this finding suggests that the interpersonal skills taught can help adolescents with trauma exposure to address challenging relationships and promote positive social support networks, which are important for promoting well-being in the face of adversity. However, it is clear from our findings that adolescents in IPT-AST with trauma exposure did not experience as notable decreases in depression symptoms as adolescents in IPT-AST who had no trauma exposure. This suggests that more needs to be done to increase the potential impact of IPT-AST for youth who have been exposed to trauma and to increase understanding of how and why youth with trauma exposure do not experience the same benefit from IPT-AST as their unexposed counterparts.

In GC, we found that youth exposed to trauma (measured cumulatively and categorically) not only experienced significant reductions in depressive symptoms during the active phase, but that these reductions were larger than those in youth with no or low trauma. This was unexpected. The greater change in youth with trauma exposure in GC may be attributed to the flexibility that GC group leaders had in tailoring the intervention to meet the needs of the youth in the group. They may have specifically targeted trauma in the group content or may have taught strategies that were particularly relevant to youth who had been exposed to trauma, such as cognitive and behavioral techniques. However, the fact that similar moderating effects have been found in CBT trials suggest that this is not entirely the explanation, as CBT was less effective for youth with trauma exposure in these studies. It is possible that the supportive structure of GC, regardless of specific content, benefits adolescents with trauma exposure.

Limitations

Although the current study’s findings are a valuable addition to the literature regarding the prevention of depression in a diverse sample of adolescents, the limitations of the study should be noted. First, the study lacked a no-intervention control condition. As such, we do not know whether youth with trauma exposure and youth without trauma exposure would have shown significant reductions in symptoms over time without any intervention, as was seen in IPT-AST and GC. Relatedly, GC was a rigorous comparison condition that resulted in significant benefits for many youth in GC. Future research should consider a treatment as usual comparison to better understand the potential benefits of IPT-AST over services as usual. Second, IPT-AST was delivered by trained psychologists and clinical psychology graduate students, an intervention model that is not scalable. Future research should investigate whether school personnel can be trained to deliver the intervention with fidelity and promote positive youth outcomes. Third, although the K-SADS-PL has been used to assess cumulative trauma exposure in prior treatment studies (Lewis et al., 2010), it is possible that a more detailed trauma assessment may have yielded different results. Relatedly, although a cumulative approach to trauma has been commonly adopted due to the high co-occurrence of traumatic events in childhood (Evans et al., 2013), others argue that the cumulative risk approach is limited in its assumption that different types of adversity will have the same impact and that factors such as chronicity and severity should be considered (McLaughlin & Sheridan, 2016). The assessment of trauma in DPI may have been insufficiently descriptive as it lacked evaluation of potentially important features of trauma such as severity, frequency, and duration. These factors have implications for the likelihood of developing depression (Maercker et al., 2004; Mullen et al., 1993) and may also have an impact on intervention response. Future studies should consider expanding the inventory of potentially traumatic experiences and should examine whether trauma-related symptoms, in addition to exposure to traumatic events, act as moderators of intervention outcomes. Fourth, given concerns about statistical power in moderation analyses, future research should examine trauma as a moderator of prevention effects in larger sample studies or in the context of a meta-analysis. Fifth, although the sample was racially and ethnically diverse, a large portion of the sample was reasonably financially secure. Prior studies of IPT-AST (e.g., Young et al., 2010, 2006; Young, Kranzler, et al., 2012; Young, Makover, et al., 2012), have been implemented in urban areas with predominately minority and low income participants, and have found positive effects of the program. Unfortunately, the sample sizes of these studies were too small to examine whether trauma moderated outcomes. Future studies of IPT-AST and other prevention programs should continue to examine whether trauma moderates outcomes, particularly in low socioeconomic and urban areas where there may be unique implementation challenges and higher rates of trauma exposure. Finally, this study examined the impact of trauma on rates of change in depressive symptoms. Future prevention studies can expand on this work by examining the impact of trauma on rates of subsequent depression diagnoses, as well as change in depressive symptoms over time.

Implications

The current findings have a number of implications. First, it is important to continue to assess the presence and extent of trauma exposure in intervention studies and to determine whether there are evidence-based interventions (prevention and treatment) that are robust to the effects of trauma. This research is needed to determine the most effective interventions and to understand for whom certain interventions will or will not be beneficial. Second, our findings suggest that youth with trauma exposure benefit from preventive interventions for depression but that the effects of IPT-AST were weaker in this population. More work needs to be done to ensure that youth who have multiple risk factors (e.g., depression symptoms and history of trauma exposure) receive appropriate and maximally effective interventions to reduce their risk for depression and other negative outcomes. This may require modifications to IPT-AST or may involve a stepped approach where IPT-AST is followed (or preceded) by an intervention that specifically targets trauma. Another option is to tailor the timing, frequency, and content of IPT-AST booster sessions to optimize intervention effects for this population. Providing boosters to adolescents on an as-needed basis may help adolescents sustain the benefits received in the short-term from prevention (Brunwasser & Garber, 2016) and provide an opportunity for ongoing social support, which may be particularly important for youth exposed to trauma (Meyerson et al., 2011). Finally, given the prevalence, negative outcomes, and diminished response to evidence-based depression interventions associated with trauma exposure, clinicians should routinely probe for possible trauma experiences to determine whether the intervention being used should be adapted to account for trauma exposure or whether a supplemental trauma-focused intervention may be needed (Sieger et al., 2004).

Footnotes

Clinical Trial Registration

This study is registered under ClinicalTrials.gov Identifier: NCT01201382.

Declaration of Conflicting Interests

Dr. Young has published a book on Interpersonal Psychotherapy-Adolescent Skills Training (IPT-AST), the focus of this paper, and receives royalties from Oxford Press.

Funding

This research was supported by the NIMH under Grant R01MH087481.

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