Characterizing the Placebo Response in Adults With ADHD

Effects of one single-dose methylphenidate compared to one single-dose placebo on QbTest performance in adults with untreated ADHD: a randomized controlled trial

BACKGROUND

Treatment of adults with attention-deficit/hyperactivity disorder (ADHD) primary involves methylphenidate (MPH). Earlier studies have identified placebo responders to increase toward the end of the treatment periods. However, little is known about the immediate effects of placebo on the core symptoms of ADHD in adults. The present study aimed to examine the effects of one single-dose MPH compared to one single-dose placebo during clinical assessments with continuous performance tests (CPT).

METHODS

In a randomized study with cross-over design, 40 adults between 19 and 64 years (72.5% women) with untreated ADHD were consecutively enrolled. The study comprised two trial days with four days in between. The QbTest was performed twice on the same day, before and 80 min after intake of one single-dose 20 mg immediate release methylphenidate (IR-MPH) and with one single-dose placebo, in randomized order.

RESULTS

Performance improved in QbInattention, F (3, 117) = 38.25, p < 0.001, after given IR-MPH (mean diff = 1.14) and after placebo (mean diff = 0.60) with the effect sizes 1.17 and 0.63 respectively. IR-MPH improved performance in QbActivity (mean diff = 0.81, p < 0.001) and QbImpulsivity (mean diff = 0.46, p < 0.04). The proportion of improvements (a decrease by ≥ 0.5 Qb-score) in the parameters QbInattention, QbActivity and QbImpulsivity were 90%, 60% and 52.5%, respectively. After given placebo, corresponding proportions were 60%, 30% and 35%, respectively.

CONCLUSIONS

There seems to be an immediate placebo response in the core symptom inattention. The effect of placebo cannot be ruled out and must be taken in consideration during drug trials with continuous performance tests (CPTs).

TRIAL REGISTRATION

ClinicalTrials.gov; Identifier: NCT02473185.

Placebo and nocebo responses in randomised, controlled trials of medications for ADHD: a systematic review and meta-analysis

The nature and magnitude of placebo and nocebo responses to ADHD medications and the extent to which response to active medications and placebo are inter-correlated is unclear. To assess the magnitude of placebo and nocebo responses to ADHD and their association with active treatment response. We searched literature until June 26, 2019, for published/unpublished double-blind, randomised placebo-controlled trials (RCTs) of ADHD medication. Authors were contacted for additional data. We assessed placebo effects on efficacy and nocebo effects on tolerability using random effects meta-analysis. We assessed the association of study design and patient features with placebo/nocebo response. We analysed 128 RCTs (10,578 children/adolescents and 9175 adults) and found significant and heterogenous placebo effects for all efficacy outcomes, with no publication bias. The placebo effect was greatest for clinician compared with other raters. We found nocebo effects on tolerability outcomes. Efficacy outcomes from most raters showed significant positive correlations between the baseline to endpoint placebo effects and the baseline to endpoint drug effects. Placebo and nocebo effects did not differ among drugs. Baseline severity and type of rating scale influenced the findings. Shared non-specific factors influence response to both placebo and active medication. Although ADHD medications are superior to placebo, and placebo treatment in clinical practice is not feasible, clinicians should attempt to incorporate factors associated with placebo effects into clinical care. Future studies should explore how such effects influence response to medication treatment. Upon publication, data will be available in Mendeley Data: PROSPERO (CRD42019130292).

Placebo Response and Its Predictors in Attention Deficit Hyperactivity Disorder: A Meta-Analysis and Comparison of Meta-Regression and MetaForest

BACKGROUND

High placebo response in attention deficit hyperactivity disorder (ADHD) can reduce medication-placebo differences, jeopardizing the development of new medicines. This research aims to (1) determine placebo response in ADHD, (2) compare the accuracy of meta-regression and MetaForest in predicting placebo response, and (3) determine the covariates associated with placebo response.

METHODS

A systematic review with meta-analysis of randomized, placebo-controlled clinical trial investigating pharmacological interventions for ADHD was performed. Placebo response was defined as the change from baseline in ADHD symptom severity assessed according to the 18-item, clinician-rated, DSM-based rating scale. The effect of study design-, intervention-, and patient-related covariates in predicting placebo response was studied by means of meta-regression and MetaForest.

RESULTS

Ninety-four studies including 6614 patients randomized to placebo were analyzed. Overall, placebo response was -8.9 points, representing a 23.1% reduction in the severity of ADHD symptoms. Cross-validated accuracy metrics for meta-regression were R2 = 0.0012 and root mean squared error = 3.3219 for meta-regression and 0.0382 and 3.2599 for MetaForest. Placebo response among ADHD patients increased by 63% between 2001 and 2020 and was larger in the United States than in other regions of the world.

CONCLUSIONS

Strong placebo response was found in ADHD patients. Both meta-regression and MetaForest showed poor performance in predicting placebo response. ADHD symptom improvement with placebo has markedly increased over the last 2 decades and is greater in the United States than the rest of the world.

Efficacy and Safety of PRC-063, Extended-Release Multilayer Methylphenidate in Adults with ADHD Including 6-Month Open-Label Extension

Objective: To evaluate the efficacy and safety of a 16-hr multilayer-release methylphenidate (PRC-063) in a community-based adult ADHD population. Method: In a double-blind study, 375 participants were randomized to one of four fixed doses of PRC-063 or placebo. The primary outcome was the ADHD-Rating Scale-5 (RS). The first 50% of double-blind completers were invited to participate in a 6-month dose-optimized open-label study to assess response and safety. Results: In total, 333 participants completed the double-blind trial; 184 entered the open-label study. PRC-063 produced greater symptom reduction in ADHD-RS-5 total score from baseline compared with placebo in the double-blind study (least-square [LS] mean = -4.7 [-7.7, -1.6], p = .003). The most frequent adverse events were headache, insomnia, and decreased appetite. No significant sleep quality impact was observed (p = .123). Significant improvements in ADHD-RS-5 scores from baseline continued through the open-label study (p < .0001), coincident with dose optimization. Conclusion: PRC-063 was well tolerated and significantly improved ADHD symptomatology in adults.

Dasotraline in adults with attention deficit hyperactivity disorder: a placebo-controlled, fixed-dose trial

In a previous study, dasotraline demonstrated efficacy at a dose of 8 mg/day in adults with attention deficit hyperactivity disorder (ADHD). The aim of the current study was to evaluate the efficacy and safety of dasotraline in doses of 4 and 6 mg/day. Adults meeting Diagnostic and Statistical Manual of Mental Disorders, 5th edition criteria for ADHD were randomized to 8 weeks of double-blind, once-daily, fixed-dose treatment with dasotraline 4 mg/day, 6 mg/day, or placebo. The primary efficacy endpoint was changed in the ADHD Rating Scale, Version IV (ADHD RS-IV) total score. Secondary efficacy endpoints included the Clinical Global Impression, Severity (CGI-S) Scale. Least squares mean reduction at week 8 in the ADHD RS-IV HV total score was not significantly greater (vs. placebo) in the dasotraline 4 mg/day group (-15.0 vs. -13.9; n.s.; or in the dasotraline 6 mg/day group (-16.5 vs. -13.9; P = 0.074; Hochberg correction). Treatment with dasotraline 6 mg/day was significant at week 8 (uncorrected) on the ADHD RS-IV total score (P = 0.037) and the CGI-S score (P = 0.011). Treatment with the 4 mg/day dose of dasotraline was NS. Treatment with dasotraline was generally well tolerated. The results provide additional evidence that supports the potential efficacy of dasotraline, in doses of 6 mg/day, in adults with ADHD.