Developmental Window of Opportunity: Implications of Parent-Child Psychotherapy for Early Childhood Depression Treatment

The Centers for Disease Control and Prevention released its “Vital Signs” report on suicide in June 2018, documenting an alarming 30% increase in the suicide rate in the United States in the past 20 years (1). Suicide, the 10th leading cause of death overall and the second leading cause of death among adolescents in the United States, is only one of three principal causes of death that have surged in occurrence. In 2016 alone, nearly 45,000 Americans died by suicide. With this alarming backdrop, Luby and colleagues’ report in this issue (2) on a randomized controlled clinical trial of a low-risk, 20-session (over 18 weeks) treatment—parent-child interaction therapy with an “emotion development” module (PCIT-ED)—for early childhood depression is timely, relevant, and encouraging. Because depression is often prominent in suicide, the trial’s findings suggest the beginnings of a promising and urgently needed new window of opportunity for preventing and short-circuiting this chronic, highly treatment resistant, relapsing childhood disorder and possibly for novel distal suicide prevention efforts. The trial’s findings are additionally exciting because PCIT-ED moves beyond targeting child depressive symptoms. Treatment begins with “standard” PCIT, delivered in the first 12 sessions, targeting parent-child interactional pattern (parent-child relationship difficulties are associated with suicide) (3), followed by eight sessions of emotion-development skills, targeting emotional competence and emotion regulation (implicated in depression as well as suicide) (3, 4). These skills are enhanced in children by training parents to be “external emotion regulator and emotion coach for the child.”

Also contributing to the trial’s importance is the pressing need for new and effective options for young children with depression. Only small to moderate effect sizes have been observed with cognitive-behavioral therapy (CBT), one of the most efficacious treatments for childhood depression (5). The need for new and effective options is magnified further by the absence of compelling data showing that antidepressants outperform placebo in childhood depression. Adding to this concern is the unknown efficacy and long-term safety of multiple medication usage in children, a practice that is on the rise (6).

Luby et al. randomly assigned 229 parent-child dyads to PCIT-ED (N=114) or to a waiting list control condition (N=115), with the latter offered PCIT-ED after completing the wait interval. All children met diagnostic criteria for early childhood major depressive disorder. Primary intent-to-treat analyses compared the parent-child dyads who were assigned to the PCIT-ED condition with those who were assigned to the waiting list condition. Study therapists received careful training, weekly supervision by the principal investigator, and weekly consultations throughout treatment. The investigators carefully ensured study integrity, treatment fidelity, and maintenance of raters’ blind to treatment assignment. Only six participants did not complete any therapy sessions, and 93 completed all sessions—an indication of high treatment acceptability, which was also evidenced by 96% of parents rating their treatment impressions as “good” or “very good.” An additional study strength is its comprehensive psychiatric assessment at baseline and after treatment, involving diagnostic interviews with the caregivers and questionnaires to assess child symptoms, emotion regulation, and guilt processing. The results indicated that children in the PCIT-ED condition had lower rates of depression, lower depression severity, and lower impairment compared with those in the waiting list condition. Child emotional functioning and parenting stress and depression were also significantly improved in PCIT-ED.

For the reasons noted above, this initial trial of PCIT-ED will, deservedly so, come to be viewed as a seminal and pioneering study. It sets the stage for tremendously important future research directions. From our perspective, PCIT-ED directions that are particularly important relate to both the study of theoretical mechanisms and the use of experimental therapeutics designs and optimization of PCIT-ED’s potential for public health impact (7).

To advance our understanding of the theoretical mechanisms that underlie the observed changes and improvements in early childhood depression, it will be important to employ research designs that explain how change is produced or mediated (7). This might involve measuring the key emotion-development skills that are targeted for enhancement—emotion regulation and guilt processing—not as outcomes but as mediators. Follow-up evaluations also are essential to understand theoretical mechanisms of change and improvement (this trial’s evaluation period was from baseline to end of treatment). Follow-up evaluations will ascertain whether treatment effects are maintained over time and whether certain emotion-development skills addressed in PCIT-ED training are indeed mutable within eight sessions, or whether more time is needed, and in turn whether lagged effects in depression are observed.

An additional comment on the importance of long-term follow-up evaluations is warranted in light of past findings that the majority of participants with depression in adolescent and adult samples who receive evidence-based treatment for depression, including CBT, subsequently experience relapse or recurrence (8). PCIT-ED’s focus on young children holds particularly exciting promise because it capitalizes on the heightened neural plasticity characterizing this early epoch in development, which may allow alteration of long-term trajectories of emotion regulation and depression and lessen the risk of relapse or recurrence. As research continues to realize this promise, it seems important to ensure that future study designs include continuation of treatment at least until remission of depression as well as regular symptom monitoring during follow-up periods to rapidly identify and intervene in recurrent episodes (8).

A related and critical aspect of this research includes identification of variables that moderate treatment response and long-term recovery. Parental depression holds promise as a candidate moderator of PCIT-ED effects. It is reasonable to hypothesize, for example, that severity of parental depression will influence the parent’s ability to fully engage in the clinical tasks required in PCIT-ED. Moreover, parental history of recurrent depression may identify families who would benefit from continuation treatment, given the documented association between parental recurrent depression and offspring risk of recurrence (9). Overall, now that initial efficacy for PCIT-ED has been demonstrated, there is considerable knowledge to be discovered through experimental therapeutic designs, including identification of variables for personalizing treatment and mechanisms of change, using not only questionnaires but also behavioral and biological measures.

Although rare in clinical trials, another intriguing possibility is that associations may exist among mediators themselves, thereby complicating the theoretical tracing of relative treatment effects. For example, improved guilt processing in young children may have statistically significant estimated effects on parenting stress, which may lead to reduced parental depression and, in turn, reduced early childhood depression. Experimental therapeutic designs with follow-ups also would allow for modeling and analyzing directional patterns of change, to better understand the significant reductions found in parental depression, although parental depression is not directly targeted (see 10).

Although the waiting list comparator was a reasonable design choice at this stage of PCIT-ED knowledge development, its duration, limited to that of the PCIT-ED study design (baseline to end of treatment), contributes to the difficulty in determining the persistence of PCIT’s effects over time. That said, “watchful waiting” can only go for so long, and there are ethical challenges involved in naturalistic long-term follow-ups. As the authors note, comparators involving more active and credible procedures are important next design steps. Especially important is to employ a comparator that does not target emotion regulation, to ensure that the effects found in PCIT-ED’s emotion regulation targets are specific to this treatment (see, for example, 10).

Finally, Luby et al. suggest that because PCIT-ED can be delivered by trained master’s-level therapists and is “a relatively brief, 20-session manualized treatment,” it is “feasible for delivery in community health settings.” We agree that PCIT-ED holds this promise, but it would seem important to consider a more streamlined treatment, given that the modal treatment attendance in community settings is one session and the median is five sessions (11). More frequent assessments during the delivery of PCIT-ED in future studies could also inform dosing parameters, to balance the realities of treatment in community settings with the need to treat depression until remission.

This first randomized controlled clinical trial of PCIT-ED by Luby and colleagues represents a critical first step in developing an evidence-based treatment research literature for early childhood depression. We expect further advances in knowledge to come through this developmental window of opportunity.