Antidepressant Tolerability in Pediatric Anxiety and Obsessive-Compulsive Disorders: A Bayesian Hierarchical Modeling Meta-analysis

The Impact of Development on Antidepressant and Placebo Response in Anxiety Disorders: A Bayesian Hierarchical Meta-Analytic Examination of Randomized Controlled Trials in Children, Adolescents, and Adults

Background: Understanding how development influences medication and placebo responses in anxiety disorders could inform treatment decisions, including age-specific first- versus second-line psychopharmacological interventions. Objective: To meta-analytically compare the trajectory of selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and placebo response in youth and adults with anxiety disorders. Methods: Weekly symptom severity data were extracted from prospective, randomized, parallel-group, placebo-controlled trials of SSRIs and SNRIs in children, adolescents, and adults with anxiety disorders (generalized, separation, and social anxiety disorders as well as panic disorder). Treatment response was modeled for the standardized change in continuous measures of anxiety using a Bayesian hierarchical model. Change in symptom severity was evaluated as a function of time, and post hoc analyses were conducted to determine the sensitivity of these results across sample heterogeneity and alternative functional forms. Results: Data were included from 11 trials of youth (SSRI, κ = 7; SNRI, κ = 4) and 71 studies of adults (SSRI, κ = 46; SNRI, κ = 25). In total, 1067 youth participated in SSRI trials and 1024 in SNRI trials. In total, 10,826 adults participated in SSRI trials (placebo, n = 5367; SSRI n = 5,459) and 6232 in SNRI trials (placebo, n = 3,128; SNRI n = 3,094). A logarithmic model best described the response. Placebo response was similar in youth and adults (mean difference = -1.98 ± 6.21, 95% credible interval [CrI]: -10.2 to 14.2, p = 0.750), and statistically significant improvement from baseline emerged by week 2 in both adults (mean difference: -18.34 + 1.017, 95% CrI: -20.3 to 16.3, p < 0.001) and youth (mean difference: -23.74 + 3.736, 95% CrI: -31.1 to -16.4, p < 0.001). SSRIs produced similar improvements for youth and adults (p = 0.129), but SNRIs produced slower improvement in youth than adults (p = 0.018). Conclusions: Antidepressant-related improvement occurs early in youth and adults with anxiety disorders. SSRI response is similar in adults and youth; however, SNRIs produce greater responses in adults than youth, potentially representing a developmental effect.

Gastrointestinal Symptoms in Pediatric Patients with Anxiety Disorders and Their Relationship to Selective Serotonin Reuptake Inhibitor Treatment or Placebo

Gastrointestinal symptoms are commonly reported as adverse effects of selective serotonin reuptake inhibitors (SSRIs), the first-line pharmacologic treatment for pediatric anxiety disorders; however, the temporal course of these symptoms during treatment, although believed to be transient, has never been prospectively evaluated. Additionally, rates of gastrointestinal symptoms and functional gastrointestinal syndromes in anxious youth are poorly understood. We examined gastrointestinal symptoms in youth with anxiety disorders during a double-blind, placebo-controlled trial of escitalopram (n = 51). Then, in a separate sample of prospectively treated children and adolescents with generalized, social and/or separation anxiety disorders (n = 56), we examined the frequency of gastrointestinal symptoms based on the Questionnaire on Pediatric Gastrointestinal Symptoms (QPGS) and ROME III criteria and the association of these symptoms with clinical and demographic characteristics using logistic regression. The frequency/severity of abdominal pain, diarrhea, bloating constipation or total gastrointestinal symptoms did not differ between patients receiving placebo (n = 25) or escitalopram (n = 26). However, escitalopram-treated youth had transient changes in nausea/vomiting and total upper gastrointestinal symptoms during the first two weeks of treatment. ROME III criteria for functional gastrointestinal syndromes were present in 12/56 patients (21.4%). QPGS-related functional gastrointestinal syndromes and symptoms were unrelated to treatment, treatment type, or clinical or demographic variables. Gastrointestinal symptoms are common in youth with anxiety and SSRIs produce transient-rather than sustained-gastrointestinal symptoms. Assessing gastrointestinal symptoms prior to pharmacotherapy and discussing factors that increase (or decrease) the likelihood of transient SSRI-related symptoms in youth may decrease patient uncertainty related to side effects and decrease medication-related anxiety.

What Is the Added Benefit of Combining Cognitive Behavioral Therapy and Selective Serotonin Reuptake Inhibitors in Youth with Obsessive Compulsive Disorder? A Bayesian Hierarchical Modeling Meta-Analysis

Background: Treatment of obsessive-compulsive disorder (OCD) in children and adolescents frequently involves cognitive behavioral therapy (CBT), selective serotonin reuptake inhibitors (SSRIs), or their combination. However, how adding CBT to SSRIs affects the trajectory and magnitude of improvement has not been evaluated meta-analytically. Methods: We performed a meta-analysis using weekly data from prospective randomized parallel group trials of CBT and SSRIs in pediatric patients with OCD. Response was modeled for the change in the Child Yale-Brown Obsessive-Compulsive Scale (CY-BOCS) using a Bayesian hierarchical model over 12 weeks. Results: Fourteen studies included pharmacotherapy arms, 4 studies included combined pharmacotherapy and psychotherapy, and 10 studies included a placebo or control arm. The studies included 1146 patients (mean age 12.7 ± 1.3 years, mean 42.1% female). In the logarithmic model of response, statistically significant differences in treatment effects for CBT+SSRI and SSRI monotherapy were observed compared with placebo (SSRI β = -3.59, credible interval [95% CrI]: -4.13 to -3.02, p < 0.001; SSRI+CBT β = -4.07, 95% CrI: -5.05 to -3.04, p < 0.001). Adding CBT to an SSRI produced numerically (but not statistically significantly) greater improvement over 12 weeks. Greater improvement was observed in studies with more boys (p < 0.001), younger patients (p < 0.001), and in studies with greater baseline symptom severity (p < 0.001). Conclusions: In children and adolescents with OCD, compared with placebo, both SSRIs and SSRI+CBT produced early and sustained improvement over 12 weeks, although the improvement was also related to sample characteristics. Longer term studies are needed to determine when the additive benefit of CBT emerges relative to SSRI monotherapy.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2D6, CYP2C19, CYP2B6, SLC6A4, and HTR2A Genotypes and Serotonin Reuptake Inhibitor Antidepressants

Serotonin reuptake inhibitor antidepressants, including selective serotonin reuptake inhibitors (SSRIs; i.e., citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline), serotonin and norepinephrine reuptake inhibitors (i.e., desvenlafaxine, duloxetine, levomilnacipran, milnacipran, and venlafaxine), and serotonin modulators with SSRI-like properties (i.e., vilazodone and vortioxetine) are primary pharmacologic treatments for major depressive and anxiety disorders. Genetic variation in CYP2D6, CYP2C19, and CYP2B6 influences the metabolism of many of these antidepressants, which may potentially affect dosing, efficacy, and tolerability. In addition, the pharmacodynamic genes SLC6A4 (serotonin transporter) and HTR2A (serotonin-2A receptor) have been examined in relation to efficacy and side effect profiles of these drugs. This guideline updates and expands the 2015 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2D6 and CYP2C19 genotypes and SSRI dosing and summarizes the impact of CYP2D6, CYP2C19, CYP2B6, SLC6A4, and HTR2A genotypes on antidepressant dosing, efficacy, and tolerability. We provide recommendations for using CYP2D6, CYP2C19, and CYP2B6 genotype results to help inform prescribing these antidepressants and describe the existing data for SLC6A4 and HTR2A, which do not support their clinical use in antidepressant prescribing.

Treatment for Anxiety Disorders in the Pediatric Primary Care Setting

Anxiety disorders are among the most diagnosed mental health problems in children and adolescents. Without intervention, anxiety disorders in youth are chronic, debilitating, and amplify risk of negative sequelae. Youth with anxiety present to primary care frequently and often families choose to first discuss mental health concerns with their pediatricians. Both behavioral and pharmacologic interventions can be effectively implemented in primary care, and research demonstrates the effectiveness of both approaches.

Advances in Pharmacotherapy for Pediatric Anxiety Disorders

The evidence base for psychopharmacologic interventions in children and adolescents with anxiety disorders has significantly increased, and our understanding of the relative efficacy and tolerability of interventions has expanded contemporaneously. Selective serotonin reuptake inhibitors (SSRIs) are the first-line pharmacologic treatment for pediatric anxiety due to their robust efficacy although other agents may have efficacy. This review summarizes the data concerning the use of SSRIs, serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, atypical anxiolytics (eg, 5HT_1A agonists, alpha agonists), and benzodiazepines in pediatric anxiety disorder cases (ie, generalized anxiety disorder, separation anxiety disorder, social anxiety disorder, and panic disorder). The extant data suggest that SSRIs and SNRIs are effective and well tolerated. SSRIs as monotherapy and SSRIs + cognitive behavioral therapy reduce symptoms in youth with anxiety disorders. However, randomized controlled trials do not suggest efficacy for benzodiazepines or the 5HT_1A agonist, buspirone, in pediatric anxiety disorder cases.

A Multicenter Double-Blind, Placebo-Controlled Trial of Escitalopram in Children and Adolescents with Generalized Anxiety Disorder

Objective: Generalized anxiety disorder (GAD) in children and adolescents is associated with substantial morbidity and increases the risk of future psychopathology. However, relatively few psychopharmacologic studies have examined treatments for GAD in pediatric populations, especially in prepubertal youth. Methods: Children and adolescents aged 7-17 years of age with a primary diagnosis of GAD were treated with flexibly dosed escitalopram (10-20 mg daily, n = 138) or placebo (n = 137) for 8 weeks. Efficacy measures included the Pediatric Anxiety Rating Scale (PARS) for GAD, Clinical Global Impression of Severity (CGI-S) scale, Children's Global Assessment Scale (CGAS); safety measures included the Columbia-Suicide Severity Rating Scale (C-SSRS) as well as adverse events (AEs), vital signs, and electrocardiographic and laboratory monitoring. Results: Escitalopram was superior to placebo in reducing anxiety symptoms of GAD, as seen in the difference in mean change from baseline to week 8 on the PARS severity for GAD score (least squares mean difference = -1.42; p = 0.028). Functional improvement, as reflected by CGAS score, was numerically greater in escitalopram-treated patients compared with those receiving placebo (p = 0.286), and discontinuation owing to AEs did not differ between the two groups. Vital signs, weight, laboratory, and electrocardiographic results were consistent with previous pediatric studies of escitalopram. Conclusions: Escitalopram reduced anxiety symptoms and was well tolerated in pediatric patients with GAD. These findings confirm earlier reports of escitalopram efficacy in adolescents aged 12-17 years and extend the safety and tolerability data to children with GAD aged 7-11 years. ClinicalTrials.gov Identifier: NCT03924323.

Adverse Effects of Antidepressant Medications and their Management in Children and Adolescents

INTRODUCTION

Selective serotonin reuptake inhibitors (SSRIs) and, to a lesser extent, serotonin-norepinephrine reuptake inhibitors (SNRIs) are the cornerstone of pharmacotherapy for children and adolescents with anxiety and depressive disorders. These medications alleviate symptoms and restore function for many youths; however, they are associated with a distinct adverse effect profile, and their tolerability may complicate treatment or lead to discontinuation. Yet, SSRI/SNRI tolerability has received limited attention in the pediatric literature.

METHODS

This review examines the early- (e.g., activation, gastrointestinal symptoms, sedation) and late-emerging (e.g., weight gain) adverse effects of SSRIs and some SNRIs in pediatric patients.

RESULTS

We provide a framework for discussing SSRI/SNRI tolerability with patients and their families and describe the pharmacologic basis, course, and predictors of adverse events in youth. Strategies to address specific tolerability concerns are presented. For selected adverse events, using posterior simulation of mean differences over time, we describe their course based on Physical Symptom Checklist measures in a prospective, randomized trial of anxious youth aged 7-17 years who were treated with sertraline (n = 139) or placebo (n = 76) for 12 weeks in the Child/Adolescent Anxiety Multimodal Study (CAMS).

MAIN RESULTS

In CAMS, the relative severity/burden of total physical symptoms (p < 0.001), insomnia (p = 0.001), restlessness (p < 0.001), nausea (p = 0.002), abdominal pain (p < 0.001), and dry mouth (p = 0.024) decreased from baseline over 12 weeks of sertraline treatment, raising the possibility that these symptoms are transient. No significant changes were observed for sweating (p = 0.103), constipation (p = 0.241), or diarrhea (p = 0.489). Finally, we review the antidepressant withdrawal syndrome in children and adolescents and provide guidance for SSRI discontinuation, using pediatric pharmacokinetic models of escitalopram and sertraline-two of the most used SSRIs in youth.

CONCLUSION

SSRI/SNRIs are associated with both early-emerging (often transient) and late-emerging adverse effects in youth. Pharmacokinetically-informed appraoches may address some adverse effects and inform SSRI/SNRI discontinuation strategies.

Pediatric Psychopharmacology for Depressive and Anxiety Disorders

Anxiety and depressive disorders are the most common psychiatric illnesses among children and adolescents. These disorders are associated with impairments in social, family, and educational functioning. This article summarizes the evidence base for psychopharmacologic interventions; the developmental pharmacology of selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs); and pharmacokinetic and pharmacodynamic differences between youths and adults that call for differences in dosage and affect response and tolerability. The authors also review the efficacy and tolerability of SSRIs and SNRIs in children and adolescents with depressive and anxiety disorder diagnoses, as well as data related to duration of therapy and SSRI/SNRI discontinuation in this population. Taken together, the current evidence suggests that SSRIs are the first-line psychopharmacologic intervention for youths with depressive and anxiety disorders, with SNRIs having a more limited role. These medications are safe and well tolerated, although emerging data and developmental pharmacologic concepts may help clinicians to choose from available SSRIs and to improve the efficacy and tolerability of these medications in children and adolescents.

Cognitive Behavioral Therapy for Anxiety Disorders in Youth: Efficacy, Moderators, and New Advances in Predicting Outcomes

PURPOSE OF REVIEW

This review integrates recent systematic reviews and meta-analyses on the efficacy of cognitive behavioral therapy (CBT) for the treatment of anxiety disorders in children and adolescents. To inform personalized approaches to intervention, we also review recent research on moderators and predictors of outcomes.

RECENT FINDINGS

Meta-analyses provide strong support for the efficacy of CBT for youth anxiety disorders, including with preschool-aged children using appropriate modifications. Furthermore, there is evidence that CBT is an effective adjunct treatment to psychopharmacological interventions, and the combination of treatments may be most effective for some youth. There is limited evidence of consistent demographic and clinical moderators of outcomes. Recent work in neuroscience has highlighted novel predictors of treatment outcomes that, with replication, may aid in more personalized approaches to youth anxiety treatment. CBT is efficacious for treating anxiety disorders in youth and lowering recurrence rates. CBT can also be an efficacious adjunct treatment for psychopharmacological interventions. Neuroimaging and psychophysiological measures of threat and motivational processing have shown initial promise in predicting symptom change with CBT, with potential implications for precision medicine.

Acute Neurofunctional Effects of Escitalopram in Pediatric Anxiety: A Double-Blind, Placebo-Controlled Trial

OBJECTIVE

Amygdala-ventrolateral prefrontal cortex (VLPFC) circuitry is disrupted in pediatric anxiety disorders, yet how selective serotonin reuptake inhibitors (SSRIs) affect this circuitry is unknown. We examined the impact of the SSRI escitalopram on functional connectivity (FC) within this circuit, and whether early FC changes predicted treatment response in adolescents with generalized anxiety disorder (GAD).

METHOD

Resting-state functional magnetic resonance (MR) images were acquired before and after 2 weeks of treatment in 41 adolescents with GAD (12-17 years of age) who received double-blind escitalopram or placebo for 8 weeks. Change in amygdala-based whole-brain FC and anxiety severity were analyzed.

RESULTS

Controlling for age, sex, and pretreatment anxiety, escitalopram increased amygdala-VLPFC connectivity compared to placebo (F = 17.79, p = .002 FWE-corrected). This early FC change predicted 76.7% of the variability in improvement trajectory in patients who received escitalopram (p < .001) but not placebo (p = .169); the predictive power of early amygdala-VLPFC FC change significantly differed between placebo and escitalopram (p = .013). Furthermore, this FC change predicted improvement better than baseline FC or clinical/demographic characteristics. Exploratory analyses of amygdala subfields' FC revealed connectivity of left basolateral amygdala (BLA) -VLPFC (F = 19.64, p < .001 FWE-corrected) and superficial amygdala-posterior cingulate cortex (F = 22.92, p = .001 FWE-corrected) were also increased by escitalopram, but only BLA-VLPFC FC predicted improvement in anxiety over 8 weeks of treatment.

CONCLUSION

In adolescents with GAD, escitalopram increased amygdala-prefrontal connectivity within the first 2 weeks of treatment, and the magnitude of this change predicted subsequent clinical improvement. Early normalization of amygdala-VLPFC circuitry might represent a useful tool for identifying future treatment responders as well as a promising biomarker for drug development.

CLINICAL TRIAL REGISTRATION INFORMATION

Neurofunctional Predictors of Escitalopram Treatment Response in Adolescents With Anxiety; https://www.clinicaltrials.gov/; NCT02818751.

The Impact of Failed Antidepressant Trials on Outcomes in Children and Adolescents with Anxiety and Depression: A Systematic Review and Meta-Analysis

Objective: To identify predictors of medication-placebo differences in double-blind placebo-controlled antidepressant trials in children and adolescents with anxiety and depression. Methods: Clinical trials in patients <18 years of age with major depressive disorder or generalized, separation or social anxiety disorders were obtained from PubMed, the Cochrane Database and clinicaltrials.gov searches from inception through 2019. Forty-nine trials (43 published and 6 unpublished) of anxiety (κ = 13) and depression (κ = 36) evaluated 19 antidepressants in 8642 child and adolescent patients; placebo and medication response rates, trial characteristics, disorder, medication class, and funding source were extracted. Antidepressant-placebo differences were examined using Bayesian hierarchical models and estimates of response were determined for trial design, disorder, and medication class variables. Using meta-regression, correlates of antidepressant-placebo difference and placebo response were examined. Results: Funding source differentiated medication-placebo differences regardless of disorder. Industry trials had larger placebo response rates (mean difference: 0.189 ± 0.066, credible interval [CrI]: 0.067 to 0.33, p = 0.0008) and smaller medication-placebo differences (-0.235 ± 0.078, CrI: -0.397 to -0.086, p = 0.005) compared with federally funded trials. However, medication response was similar for industry- and federally-funded studies (-0.046 ± 0.042, CrI: -0.130 to 0.038, p = 0.252). Conclusions: The impact of study sponsorship on trial outcome supports the assertion that industry-funded trials with high placebo response rates and small drug-placebo differences are "failed trials" and should not be described as "negative trials" or used to determine public health estimates of antidepressant efficacy in children and adolescents with anxiety and depression. Identifying the proper role and value of industry-funded trials is critical to establishing the evidence base for antidepressants in youth.

Computational Predictions for OCD Pathophysiology and Treatment: A Review

Obsessive compulsive disorder (OCD) can manifest as a debilitating disease with high degrees of co-morbidity as well as clinical and etiological heterogenity. However, the underlying pathophysiology is not clearly understood. Computational psychiatry is an emerging field in which behavior and its neural correlates are quantitatively analyzed and computational models are developed to improve understanding of disorders by comparing model predictions to observations. The aim is to more precisely understand psychiatric illnesses. Such computational and theoretical approaches may also enable more personalized treatments. Yet, these methodological approaches are not self-evident for clinicians with a traditional medical background. In this mini-review, we summarize a selection of computational OCD models and computational analysis frameworks, while also considering the model predictions from a perspective of possible personalized treatment. The reviewed computational approaches used dynamical systems frameworks or machine learning methods for modeling, analyzing and classifying patient data. Bayesian interpretations of probability for model selection were also included. The computational dissection of the underlying pathology is expected to narrow the explanatory gap between the phenomenological nosology and the neuropathophysiological background of this heterogeneous disorder. It may also contribute to develop biologically grounded and more informed dimensional taxonomies of psychopathology.

Association of Selective Serotonin Reuptake Inhibitors With the Risk of Type 2 Diabetes in Children and Adolescents

IMPORTANCE

Concerns exist that use of selective serotonin reuptake inhibitors (SSRIs) increases the risk of developing type 2 diabetes (T2D) in adults, but evidence in children and adolescents is limited. In the absence of a randomized clinical trial, evidence must be generated using real-world data.

OBJECTIVE

To evaluate the safety of SSRI use in children and adolescents with respect to the associated risk of T2D.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study of patients aged 10 to 19 years with a diagnosis for an SSRI treatment indication was conducted within the nationwide Medicaid Analytic eXtract (MAX; January 1, 2000, to December 31, 2014) and the IBM MarketScan (January 1, 2003, to September 30, 2015) databases. Data were analyzed from November 1, 2018, to December 6, 2019.

EXPOSURES

New users of an SSRI medication and comparator groups with no known metabolic adverse effects (no antidepressant exposure, bupropion hydrochloride exposure, or psychotherapy exposure). Within-class individual SSRI medications were compared with fluoxetine hydrochloride.

MAIN OUTCOMES AND MEASURES

Incident T2D during follow-up. Intention-to-treat effects were estimated using Cox proportional hazards regression models, adjusting for confounding through propensity score stratification. As-treated effects to account for continuous treatment were estimated using inverse probability weighting and marginal structural models.

RESULTS

A total of 1 582 914 patients were included in the analysis (58.3% female; mean [SD] age, 15.1 [2.3] years). The SSRI-treated group included 316 178 patients in the MAX database (publicly insured; mean [SD] age, 14.7 [2.1] years; 62.2% female) and 211 460 in the MarketScan database (privately insured; mean [SD] age, 15.8 [2.3] years; 63.9% female) with at least 2 SSRI prescriptions filled, followed up for a mean (SD) of 2.3 (2.0) and 2.2 (1.9) years, respectively. In publicly insured patients, initiation of SSRI treatment was associated with a 13% increased hazard of T2DM (intention-to-treat adjusted hazard ratio [aHR], 1.13; 95% CI, 1.04-1.22) compared with untreated patients. The association strengthened for continuous SSRI treatment (as-treated aHR, 1.33; 95% CI, 1.21-1.47), corresponding to 6.6 (95% CI, 4.2-10.4) additional cases of T2D per 10 000 patients treated for at least 2 years. Adjusted HRs were lower in privately insured patients (intention-to-treat aHR, 1.01 [95% CI, 0.84-1.23]; as-treated aHR, 1.10 [95% CI, 0.88-1.36]). Findings were similar when comparing SSRI treatment with psychotherapy (publicly insured as-treated aHR, 1.44 [95% CI, 1.25-1.65]; privately insured as-treated aHR, 1.21 [95% CI, 0.93-1.57]), whereas no increased risk was observed compared with bupropion treatment publicly insured as-treated aHR, 1.01 [95% CI, 0.79-1.29]; privately insured as-treated aHR, 0.87 [95% CI, 0.44-1.70]). For the within-class analysis, no medication had an increased hazard of T2D compared with fluoxetine.

CONCLUSIONS AND RELEVANCE

These findings suggest that children and adolescents initiating SSRI treatment may be at a small increased risk of developing T2D, particularly publicly insured patients. The magnitude of association was more modest than previously reported, and the absolute risk was small. The potential small risk should be viewed in relation to the efficacy of SSRIs for its major indications in young patients.

Treatment-Resistant Depression in Adolescents: Clinical Features and Measurement of Treatment Resistance

Objective: To describe the clinical characteristics of adolescents with antidepressant treatment-resistant major depressive disorder (MDD) and to examine the utility of the Antidepressant Treatment Record (ATR) in categorizing treatment resistance in this population. Methods: Adolescents with treatment-resistant MDD enrolled in an interventional study underwent a baseline evaluation with the ATR, Children's Depression Rating Scale-Revised (CDRS-R), and Clinical Global Impressions-Severity (CGI-S) scales. Demographic and clinical characteristics were examined with regard to ATR-defined level of resistance (level 1 to ≥3) using analysis of variance and χ² tests. Results: In adolescents with treatment-resistant MDD (N = 97), aged 12-21 years, most were female (65%), white (89%), and had recurrent illness (78%). Patients were severely ill (median CGI-S score of 5), had a mean CDRS-R score of 63 ± 10, and 17.5% had been hospitalized for depression-related symptoms. Fifty-two patients were classified as ATR 1, whereas 32 were classified as ATR level 2 and 13 patients as ≥3, respectively. For increasing ATR-defined levels, illness duration increased from 12.0 (range: 1.5-31.9) to 14.8 (range: 1.8-31.7) to 19.5 (range: 2.5-36.2) months and the likelihood of treatment with serotonin norepinephrine reuptake inhibitors (SNRIs) and dopamine norepinephrine reuptake inhibitors (DNRIs) similarly increased (p = 0.006 for both SNRIs and DNRIs) as did the likelihood of treatment with mixed dopamine serotonin receptor antagonists (χ² = 17, p < 0.001). Conclusions: This study underscores the morbidity and chronicity of treatment-resistant MDD in adolescents. The present characterization of related clinical features describes the use of nonselective serotonin reuptake inhibitors in adolescents with treatment-resistant depression and raises the possibility that those with the greatest medication treatment resistance are less likely to have had recurrent episodes. The study also demonstrates the utility of the ATR in categorizing treatment resistance in adolescents with MDD.