Neurocognitive effects of methylphenidate in adults with attention-deficit/hyperactivity disorder: A meta-analysis

The effects of chronic administration of stimulant and non-stimulant medications on executive functions in ADHD: A systematic review and meta-analysis

Attention-Deficit/Hyperactivity Disorder (ADHD) is associated with executive function deficits that are improved with medications. However, meta-analyses of stimulant effects on cognition have mostly tested single-dose effects, and there is no meta-analysis of non-stimulant effects. This systematic review and meta-analysis tested the clinically more relevant longer-term effects of Methylphenidate (20 studies; minimum 1 week) and Atomoxetine (8 studies; minimum 3 weeks) on reaction time, attention, inhibition, and working memory, searching papers on PubMed, Embase, Ovid MEDLINE, and PsycINFO. The meta-analysis of 18 studies in 1667 subjects showed that methylphenidate was superior to placebo in all cognitive domains with small to medium effect sizes (Hedges g of 0.34-0.59). The meta-analysis of atomoxetine included 7 studies in 829 subjects and showed no effects in working memory, but superior effects in the other domains with medium to large effect sizes (Hedge's g of 0.36-0.64). Meta-regression analysis showed no drug differences on cognitive effects. The meta-analyses show for the first time that chronic Methylphenidate and Atomoxetine have comparable effects of improving executive functions in people with ADHD.

A Randomized, Phase 3, Double-Blind, Crossover Comparison of Multilayer, Extended-Release Methylphenidate (PRC-063), and Lisdexamfetamine in the Driving Performance of Young Adults With ADHD

OBJECTIVE

To compare PRC-063 (multilayer-release methylphenidate) and lisdexamfetamine dimesylate (LDX) on the driving performance of young adults with attention deficit hyperactivity disorder (ADHD) in a randomized, double-blind, crossover study.

METHOD

Following up to 21 days of each treatment in each treatment course (PRC-063/LDX or LDX/PRC-063), subjects completed a 15-hour driving simulator laboratory assessment. The primary outcome measure was the Tactical Driving Quotient (TDQ) and the Clinical Global Impressions-Improvement (CGI-I) scale was a secondary outcome measure.

RESULTS

Forty-four subjects completed the study. PRC-063 and LDX had equivalent effects on driving performance through a 15-hour time period (least square mean difference -0.3 [standard error 1.08], 95% confidence interval [-2.4, 1.8], p = .793). Consistent improvement in CGI-I was observed. The incidence of treatment-emergent adverse events was similar for each treatment sequence.

CONCLUSIONS

PRC-063 and LDX had comparable effects on driving performance, from 1 through 15 hours, the last time point measured.

A systematic meta-review of systematic reviews on attention deficit hyperactivity disorder

BACKGROUND

There are now hundreds of systematic reviews on attention deficit hyperactivity disorder (ADHD) of variable quality. To help navigate this literature, we have reviewed systematic reviews on any topic on ADHD.

METHODS

We searched MEDLINE, PubMed, PsycINFO, Cochrane Library, and Web of Science and performed quality assessment according to the Joanna Briggs Institute Manual for Evidence Synthesis. A total of 231 systematic reviews and meta-analyses met the eligibility criteria.

RESULTS

The prevalence of ADHD was 7.2% for children and adolescents and 2.5% for adults, though with major uncertainty due to methodological variation in the existing literature. There is evidence for both biological and social risk factors for ADHD, but this evidence is mostly correlational rather than causal due to confounding and reverse causality. There is strong evidence for the efficacy of pharmacological treatment on symptom reduction in the short-term, particularly for stimulants. However, there is limited evidence for the efficacy of pharmacotherapy in mitigating adverse life trajectories such as educational attainment, employment, substance abuse, injuries, suicides, crime, and comorbid mental and somatic conditions. Pharmacotherapy is linked with side effects like disturbed sleep, reduced appetite, and increased blood pressure, but less is known about potential adverse effects after long-term use. Evidence of the efficacy of nonpharmacological treatments is mixed.

CONCLUSIONS

Despite hundreds of systematic reviews on ADHD, key questions are still unanswered. Evidence gaps remain as to a more accurate prevalence of ADHD, whether documented risk factors are causal, the efficacy of nonpharmacological treatments on any outcomes, and pharmacotherapy in mitigating the adverse outcomes associated with ADHD.

Methylphenidate modulates motor cortical dynamics and behavior

Methylphenidate (MPH, brand: Ritalin) is a common stimulant used both medically and non-medically. Though typically prescribed for its cognitive effects, MPH also affects movement. While it is known that MPH noncompetitively blocks the reuptake of catecholamines through inhibition of dopamine and norepinephrine transporters, a critical step in exploring how it affects behavior is to understand how MPH directly affects neural activity. This would establish an electrophysiological mechanism of action for MPH. Since we now have biologically-grounded network-level hypotheses regarding how populations of motor cortical neurons plan and execute movements, there is a unique opportunity to make testable predictions regarding how systemic MPH administration - a pharmacological perturbation - might affect neural activity in motor cortex. To that end, we administered clinically-relevant doses of MPH to Rhesus monkeys as they performed an instructed-delay reaching task. Concomitantly, we measured neural activity from dorsal premotor and primary motor cortex. Consistent with our predictions, we found dose-dependent and significant effects on reaction time, trial-by-trial variability, and movement speed. We confirmed our hypotheses that changes in reaction time and variability were accompanied by previously established population-level changes in motor cortical preparatory activity and the condition-independent signal that precedes movements. We expected changes in speed to be a result of changes in the amplitude of motor cortical dynamics and/or a translation of those dynamics in activity space. Instead, our data are consistent with a mechanism whereby the neuromodulatory effect of MPH is to increase the gain and/or the signal-to-noise of motor cortical dynamics during reaching. Continued work in this domain to better understand the brain-wide electrophysiological mechanism of action of MPH and other psychoactive drugs could facilitate more targeted treatments for a host of cognitive-motor disorders.

Single-dose effects of methylphenidate and atomoxetine on functional connectivity during an n-back task in boys with ADHD

RATIONALE

Working memory deficits and associated neurofunctional abnormalities are frequently reported in attention-deficit/hyperactivity disorder (ADHD). Methylphenidate and atomoxetine improve working memory performance and increase activation of regions under-functioning in ADHD. Additionally, methylphenidate has been observed to modulate functional networks involved in working memory. No research, however, has examined the effects of atomoxetine or compared the two drugs.

OBJECTIVES

This study aimed to test methylphenidate and atomoxetine effects on functional connectivity during working memory in boys with ADHD.

METHODS

We tested comparative effects of methylphenidate and atomoxetine on functional connectivity during the n-back task in 19 medication-naïve boys with ADHD (10-15 years old) relative to placebo and assessed potential normalisation effects of brain dysfunctions under placebo relative to 20 age-matched neurotypical boys. Patients were scanned in a randomised, double-blind, cross-over design under single doses of methylphenidate, atomoxetine, and placebo. Controls were scanned once, unmedicated.

RESULTS

Patients under placebo showed abnormally increased connectivity between right superior parietal gyrus (rSPG) and left central operculum/insula. This hyperconnectivity was not observed when patients were under methylphenidate or atomoxetine. Furthermore, under methylphenidate, patients showed increased connectivity relative to controls between right middle frontal gyrus (rMFG) and cingulo-temporo-parietal and striato-thalamic regions, and between rSPG and cingulo-parietal areas. Interrogating these networks within patients revealed increased connectivity between both rMFG and rSPG and right supramarginal gyrus under methylphenidate relative to placebo. Nonetheless, no differences across drug conditions were observed within patients at whole brain level. No drug effects on performance were observed.

CONCLUSIONS

This study shows shared modulating effects of methylphenidate and atomoxetine on parieto-insular connectivity but exclusive effects of methylphenidate on connectivity increases in fronto-temporo-parietal and fronto-striato-thalamic networks in ADHD.

Networks of Neuropsychological Functions in the Clinical Evaluation of Adult ADHD

This study applied network analysis to explore the relations between neuropsychological functions of individuals in the clinical evaluation of attention-deficit/hyperactivity disorder (ADHD) in adulthood. A total of 319 participants from an outpatient referral context, that is, 173 individuals with ADHD (ADHD group) and 146 individuals without ADHD (n-ADHD group), took part in this study and completed a comprehensive neuropsychological assessment. A denser network with stronger global connectivity was observed in the ADHD group compared to the n-ADHD group. The strongest connections were consistent in both networks, that is, the connections between selective attention and vigilance, and connections between processing speed, fluency, and flexibility. Further centrality estimation revealed attention-related variables to have the highest expected influence in both networks. The observed relationships between neuropsychological functions, and the high centrality of attention, may help identify neuropsychological profiles that are specific to ADHD and optimize neuropsychological assessment and treatment planning of individuals with cognitive impairment.

Systematic Review and Meta-Analysis of the Placebo Effect and its Correlates in Obsessive Compulsive Disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a major mental health condition with a lifetime prevalence rate of 1.3% among adults. While placebo effects are well described for conditions such as depressive and anxiety disorders, they have not been systematically characterized in OCD.

OBJECTIVES

We aimed to determine the impact of placebos in improving different symptom domains in patients with OCD.

METHODS

We systematically searched PubMed, EMBASE, Scopus, Web of Science, Ovid, the Cochrane Library, and Google Scholar databases/search engine from inception to January 2021 for randomized controlled trials of treatments for OCD with a placebo arm. A modified Cohen's effect size (ES) was calculated using change in baseline to endpoint scores for different measurement scales within placebo arms to estimate placebo effects and to investigate their correlates by random-effects model meta-analyses.

RESULTS

Forty-nine clinical trials (placebo group n  =  1993), reporting 80 OCD specific (153 measures in general) were included in the analysis. Overall placebo ES (95% confidence interval [CI]) was 0.32 (0.22-0.41) on OCD symptoms, with substantial heterogeneity (I-square = 96.1%). Among secondary outcomes, general scales, ES: 0.27 (95%CI: 0.14-0.41), demonstrated higher ES than anxiety and depression scales, ES: 0.14 (95%CI: -0.4 to 0.32) and 0.05 (95%CI: -0.05 to 0.14), respectively. Clinician-rated scales, ES: 0.27(95%CI: 0.20-0.34), had a higher ES than self-reported scales, ES: 0.07 (95%CI: -0.08 to 0.22). More recent publication year, larger placebo group sample size, shorter follow-up duration, and younger age of participants were all associated with larger placebo ES. Egger's test reflected possible small-study effect publication bias (P  =  0.029).

CONCLUSION

Placebo effects are modest in OCD trials and are larger in clinician ratings, for younger patients, and early in the treatment course. These findings underscore the need for clinicians and scientists to be mindful of placebo effects when formulating treatments or research trials for OCD.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42019125979.

Successful Treatment of Post-COVID-19 ADHD-like Syndrome: A Case Report

Despite inattention being one of the most common symptoms of Post-COVID-19 Syndrome (PCS), there is a gap in the literature regarding its treatment. This report presents a case of attentional symptoms and fatigue that emerged after the SARS-CoV-2 infection. The symptoms were similar to ADHD in adults, although the 61-year-old patient had never experienced inattention symptoms before. The patient was initially treated with Methylphenidate and then Lisdexamfetamine. Both were adapted to the needs and treatment response presented by the patient. After several changes in the therapeutic regimen, including the addition of Bupropion, the patient achieved remission of his symptoms. This case highlights the importance of treating PCS inattention and fatigue as an ADHD-like syndrome, despite the evident different etiology of symptoms. It would be necessary to replicate these findings to confirm our results, thus benefiting other patients currently affected by this syndrome.

The effects of long-term methylphenidate administration and withdrawal on progressive ratio responding and T2 MRI in the male rhesus monkey

Methylphenidate is a frequently prescribed drug treatment for Attention-Deficit/Hyperactivity Disorder. However, methylphenidate has a mode of action similar to amphetamine and cocaine, both powerful drugs of abuse. There is lingering concern over the long-term safety of methylphenidate, especially in a pediatric population, where the drug may be used for years. We performed a long-term evaluation of the effects of chronic methylphenidate use on a behavioral measure of motivation in male rhesus monkeys. Animals were orally administered a sweetened methylphenidate solution (2.5 or 12.5 mg/kg, twice a day, Mon-Fri) or vehicle during adolescence and into adulthood. These animals were assessed on a test of motivation (progressive ratio responding), during methylphenidate treatment, and after cessation of use. Moreover, animals were evaluated with quantitative T₂ MRI about one year after cessation of use. During the administration phase of the study animals treated with a clinically relevant dose of methylphenidate generally had a higher rate of responding than the control group, while the high dose group generally had a lower rate of responding. These differences were not statistically significant. In the month after cessation of methylphenidate, responding in both experimental groups dropped compared to their previous level of performance (p = 0.19 2.5 mg/kg, p = 0.06 12.5 mg/kg), and responding in the control animals was unchanged (p = 0.81). While cessation of methylphenidate was associated with an acute reduction in responding, group differences were not observed in the following months. These data suggest that methylphenidate did not have a significant impact on responding, but withdrawal from methylphenidate did cause a temporary change in motivation. No changes in T₂ MRI values were detected when measured about one year after cessation of treatment. These data suggest that long-term methylphenidate use does not have a negative effect on a measure of motivation or brain function / microstructure as measured by quantitative T₂ MRI. However, cessation of use might be associated with temporary cognitive changes, specifically alteration in motivation. Importantly, this study modeled use in healthy individuals, and results may differ if the same work was repeated in a model of ADHD.

Personalization of pharmacological treatments for ADHD: Why it is advisable and possible options to achieve it

Abstract:

Attention-deficit hyperactivity disorder is a neurodevelopmental disorder diagnosed primarily in children, although it is also present in adults. Patients present inattention, impulsivity, and hyperactivity symptoms that create difficulties in their daily lives. Pharmacological treatment with stimulants or non-stimulants is used most commonly to reduce ADHD symptoms. Although generally effective and safe, pharmacological treatments have different effects among patients, including lack of response and adverse reactions. The reasons for these differences are not fully understood, but they may derive from the highly diverse etiology of ADHD. Strategies to guide optimal pharmacological treatment selection on the basis of individual patients’ physiological markers are being developed. In this review, we describe the main pharmacological ADHD treatments used and their main drawbacks. We present alternatives under study that would allow the customization of pharmacological treatments to overcome these drawbacks and achieve more reliable improvement of ADHD symptoms.

Efficacy of cognitive behavioural therapy in medicated adults with attention-deficit/hyperactivity disorder in multiple dimensions: a randomised controlled trial

The study aimed to evaluate the efficacy of group cognitive behavioural therapy (CBT) in medicated adults with attention-deficit/hyperactivity disorder (ADHD) with a multidimensional evaluation and follow-up to week 36. Ninety-eight adult ADHD were randomly allocated to the CBT combined with medication (CBT + M) group or the medication (M) only group. The primary endpoint was the ADHD-Rating Scale (ADHD-RS). Secondary endpoints included emotional symptoms, self-esteem, automatic thoughts, quality of life (QoL), and executive function (EF). The outcome measures were obtained at baseline (T1), after the 12-week CBT treatment (T2), and at two follow-up time points (week 24, T3, and week 36, T4). Compared to the M-only group, the patients in the CBT + M group showed an overall significantly greater reduction from baseline in ADHD core symptoms (ADHD-RS total score at T3, and inattention subscale at T2 and T3), depression and anxiety symptoms (T2-T4), state anxiety (T2 and T3) and trait anxiety (T2), automatic thoughts questionnaire at T3, and QoL (physical domain, psychological domain, and social domain, most significant at T3 and weakened at T4). These findings further confirmed the efficacy of CBT on multiple dimensions and verified improvements in automatic thinking in adult ADHD. The superiority of the combination treatment mainly manifested in reduced inattention, emotional symptoms, and maladaptive thoughts and improved QoL. Trial registration number ChiCTR1900021705 (March-05-2019).

The effect of methylphenidate and mixed amphetamine salts on cognitive reflection: a field study

RATIONALE

Methylphenidate (MPH) and mixed D,L-amphetamine salts (MASs; Adderall) were previously found to have unreliable effects on judgment and decision processes.

OBJECTIVE

We predicted that MPH and MASs have a specific effect of reducing heuristic responses, which should lead to increased performance on the cognitive reflection test (CRT). The CRT is considered to be a testbed for heuristic versus deliberative response modes.

METHODS

We recruited a sample of 15,361 individuals using the Prolific Academic crowdsourcing platform. From this initial pool, our final sample consisted of 294 participants (125 MPH users and 169 MASs users) who conformed to the study criteria and completed the experimental tasks. Tasks were performed on days where participants were either medicated or not, allowing to assess the effect of medication status.

RESULTS

There was a strong positive effect of taking MPH on CRT scores (Cohen's d = 0.40) which was not qualified by frequency of MPH usage, ADHD symptoms, and demographic factors. There was also a somewhat weaker effect for MASs (Cohen's d = 0.07). No effects of MPH and MASs were recorded for risk-taking and numeracy.

CONCLUSIONS

The results indicate that MPH enhances decision-making in tasks where heuristic responses typically bias it.

First‐Dose Methylphenidate‐Induced Changes in the Anti‐Saccade Task Performance and Outcome in Adults with Attention‐Deficit/Hyperactivity Disorder

Objective

We examined whether the anti‐saccade task (AST) performance after the first methylphenidate (MPH) dose could be associated with subsequent clinical outcome in adults with attention‐deficit/hyperactivity disorder (ADHD).

Methods

Ninety‐seven drug‐naive DSM‐5 ADHD adults participated in this study. The AST parameters were measured at baseline, after the first MPH‐dose (10 mg orally), and 6 months after chronic MPH treatment. Results were compared with those of 50 healthy control (HC) subjects.

Results

At baseline, ADHDs showed longer saccadic reaction times and more direction errors than HCs (both p < 0.00001). Acute and chronic MPH administration resulted in normalization of the AST performances. Multivariate regression analysis after adjusting for age, sex, weight, and severity of symptoms at baseline, revealed that a low percentage of direction errors after the first MPH‐dose (i.e., ≤10%) could predict remission at month 6 (OR: 5.84; 95% CI: 2.00–17.11; p = 0.001).

Conclusions

Our findings indicate that: (1) impairments of motor planning and response inhibition in adults with ADHD are improved with MPH, and (2) a low direction error percentage after the first MPH‐dose may be an independent predictor of remission.

ClinicalTrials.gov identifier: NCT03411434

The antisaccade task (AST) is useful to reveal impairments in inhibitory control in ADHD.

Never‐medicated adult ADHD subjects show delays in reaction times and increased direction errors.

Methyphenidate (MPH) administration, either acute or chronic, normalizes AST performances.

Direction error percentages after the first MPH‐dose could predict treatment outcome.

Neurotherapeutics for Attention Deficit/Hyperactivity Disorder (ADHD): A Review

This review focuses on the evidence for neurotherapeutics for attention deficit/hyperactivity disorder (ADHD). EEG-neurofeedback has been tested for about 45 years, with the latest meta-analyses of randomised controlled trials (RCT) showing small/medium effects compared to non-active controls only. Three small studies piloted neurofeedback of frontal activations in ADHD using functional magnetic resonance imaging or near-infrared spectroscopy, finding no superior effects over control conditions. Brain stimulation has been applied to ADHD using mostly repetitive transcranial magnetic and direct current stimulation (rTMS/tDCS). rTMS has shown mostly negative findings on improving cognition or symptoms. Meta-analyses of tDCS studies targeting mostly the dorsolateral prefrontal cortex show small effects on cognitive improvements with only two out of three studies showing clinical improvements. Trigeminal nerve stimulation has been shown to improve ADHD symptoms with medium effect in one RCT. Modern neurotherapeutics are attractive due to their relative safety and potential neuroplastic effects. However, they need to be thoroughly tested for clinical and cognitive efficacy across settings and beyond core symptoms and for their potential for individualised treatment.

The influence of early exposure to methylphenidate on addiction-related behaviors in mice

Methylphenidate (MET) has a putative cognitive enhancer effect that has led adolescents and young adults to increase and indiscriminate its use aiming to ameliorate their productivity. However, the impacts of MET on addiction-related behaviors, emotional levels, and cognition are still not fully understood. To investigate the influence of chronic treatment with MET during adolescence on addiction-like behaviors, memory, and anxiety in adult mice. Thirty-day-old female mice received i.p. 10 mg/kg MET or Veh injections for 10 consecutive days. Forty days after the treatment (mice were 70-days-old), animals were submitted to the behavioral evaluation under the effects of MET, which included: MET-induced conditioned place preference (CPP), behavioral sensitization, and plus-maze discriminative avoidance task. Pre-exposure to MET during adolescence promoted an early expression of CPP and also facilitated the development of MET-induced behavioral sensitization during adulthood. These addictive-like behaviors were accompanied by anxiogenic effects of MET but not by any memory-enhancing effect. We demonstrated that exposure to MET during adolescence can increase the vulnerability to addiction-like behaviors and anxiety during adulthood. Our results reinforce the necessity of a more efficient system to control MET indiscriminate use, thus avoiding its potential tardive addictive effects.

A Randomized, Double-Blind, Placebo-Controlled, Two-Way Crossover Clinical Trial of ORADUR-Methylphenidate for Treating Children and Adolescents with Attention-Deficit/Hyperactivity Disorder

Objective: Methylphenidate (MPH) is efficacious in reducing symptoms of attention-deficit/hyperactivity disorder (ADHD), but there are no data about the efficacy and safety of its new formulation (ORADUR^®-MPH extended release, ORADUR-MPH) in patients with ADHD, which is the study objective. Method: This was a Phase III, multicenter, randomized, double-blind, placebo-controlled, two-way crossover clinical trial. One hundred children and adolescents with a clinical diagnosis of ADHD (72.7% male) received at least one dose of ORADUR-MPH or a placebo during the 2-week treatment period of each phase. The primary efficacy measure was the Swanson, Nolan, and Pelham-IV-teacher (SNAP-IV-T) form. Secondary efficacy measures included the SNAP-IV-parent form, the Clinical Global Impression: ADHD-Severity score, the Conner's Teacher's Rating Scale score, and the investigator's rating for 18 Diagnostic and Statistical Manual of Mental Disorders, 5th edition ADHD symptoms. In addition, data related to vital signs, body weight, physical examination, laboratory testing, and adverse events (AEs) were also collected. All data were analyzed on an intent-to-treat basis. Results: Without adjusting for differences in demographics and baseline measures, both treatment groups showed significant reductions in ADHD and oppositional defiant disorder symptoms after a 2-week treatment with greater effect sizes (Cohen's d) in the ORADUR-MPH group (Cohen's d ranging from -0.41 to -1.64; placebo, Cohen's d ranging from -0.26 to -1.18), except for oppositional symptoms, regardless of the informants. For the primary efficacy measure, ORADUR-MPH was significantly superior to the placebo, as evidenced by lower values for and greater reductions in the SNAP-IV-T scores at the endpoint (Cohen's d = -0.16, p = 0.005) and from baseline to the endpoint (Cohen's d = -0.19, p = 0.006), respectively. There were no serious AEs during the clinical study period. The most frequently observed AE was decreased appetite (49.1%). Most physical and laboratory test variables remained within the normal range. Conclusions: Once-daily ORADUR-MPH is an effective, well-tolerable, and safe treatment for children and adolescents with ADHD. ClinicalTrials.gov number, NCT02450890.

ADHD: Reviewing the Causes and Evaluating Solutions

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder in which patients present inattention, hyperactivity, and impulsivity. The etiology of this condition is diverse, including environmental factors and the presence of variants of some genes. However, a great diversity exists among patients regarding the presence of these ADHD-associated factors. Moreover, there are variations in the reported neurophysiological correlates of ADHD. ADHD is often treated pharmacologically, producing an improvement in symptomatology, albeit there are patients who are refractory to the main pharmacological treatments or present side effects to these drugs, highlighting the importance of developing other therapeutic options. Different non-pharmacological treatments are in this review addressed, finding diverse results regarding efficacy. Altogether, ADHD is associated with different etiologies, all of them producing changes in brain development, leading to the characteristic symptomatology of this condition. Given the heterogeneous etiology of ADHD, discussion is presented about the convenience of personalizing ADHD treatment, whether pharmacological or non-pharmacological, to reach an optimum effect in the majority of patients. Approaches to personalizing both pharmacological therapy and neurofeedback are presented.

Attention-deficit/hyperactivity disorder and the explore/exploit trade-off

The ability to maximize rewards and minimize the costs of obtaining them is vital to making advantageous explore/exploit decisions. Exploratory decisions are theorized to be greater among individuals with attention-deficit/hyperactivity disorder (ADHD), potentially due to deficient catecholamine transmission. Here, we examined the effects of ADHD status and methylphenidate, a common ADHD medication, on explore/exploit decisions using a 6-armed bandit task. We hypothesized that ADHD participants would make more exploratory decisions than controls, and that MPH would reduce group differences. On separate study days, adults with (n = 26) and without (n = 23) ADHD completed the bandit task at baseline, and after methylphenidate or placebo in counter-balanced order. Explore/exploit decisions were modeled using reinforcement learning algorithms. ADHD participants made more exploratory decisions (i.e., chose options without the highest expected reward value) and earned fewer points than controls in all three study days, and methylphenidate did not affect these outcomes. Baseline exploratory choices were positively associated with hyperactive ADHD symptoms across all participants. These results support several theoretical models of increased exploratory choices in ADHD and suggest the unexplained variance in ADHD decisions may be due to less value tracking. The inability to suppress actions with little to no reward value may be a key feature of hyperactive ADHD symptoms.

Cognitive deficits and psychosocial functioning in adult ADHD: Bridging the gap between objective test measures and subjective reports

INTRODUCTION

Self-reported cognitive deficits in adult Attention-Deficit/Hyperactivity-Disorder (ADHD) are often not corroborated by standardized tests. Tests and reports also differ in their correspondence to aspects of psychosocial functioning. Executive function tasks (EF-tasks) using material close to daily life, may provide a more ecologically-valid assessment of cognitive deficits.

METHOD

36 adults with ADHD and 36 healthy controls performed standardized EF-tasks and corresponding EF-tasks using material close to daily life and gave self-reports on cognitive functioning. The study investigated performance differences and the predictive utility of cognitive measures for psychosocial functioning.

RESULTS

While all the self-reports showed substantial cognitive impairments for the ADHD group, this was only shown in some of task measures. For two domains, the deficits in EF-tasks with material close to daily life were similar or smaller than assessed with traditional measures. However, three tasks, which used material of daily life, revealed more deficits than the corresponding more standardized tasks. Beyond cognitive self-reports the new tasks did not contribute substantial to psychosocial functioning, similar to the standardized tasks.

CONCLUSIONS

Tasks using material close to daily life have the potential to objectify reported everyday life deficits better than more standardized tests, at least in single EF-domains. When relevant methodical aspects of these tasks will be more targeted and considered systematically in future research, the tasks might contribute to assessments of psychosocial functioning. Then they could also be used as outcome measures in intervention studies.

An update on the clinical pharmacology of methylphenidate: therapeutic efficacy, abuse potential and future considerations

INTRODUCTION

Methylphenidate remains a first-line medication for treating ADHD in children and adults. However, its behavioral pharmacological similarities to methamphetamine and cocaine have historically created concern for its potential as a drug of abuse. In September 2019, the FDA published a docket requesting comments for the development of abuse deterrent formulations for CNS stimulants, emphasizing the abuse of methylphenidate as a public health concern.

AREAS COVERED

We conducted a narrative review of research on the clinical pharmacology, therapeutic efficacy, and abuse potential of methylphenidate.

EXPERT OPINION

Several studies indicate that methylphenidate has at least some abuse potential. Methylphenidate, amphetamine, methamphetamine, and cocaine overlap in their subjective, reinforcing, and discriminative stimulus effects. Regardless, methylphenidate remains an efficacious treatment for ADHD in children and adults when properly adhered to, especially when paired with non-pharmacological treatments. The development of abuse deterrent formulations of methylphenidate is warranted.

Effects of working memory training on emotion regulation: Transdiagnostic review

Working memory training is widely used transdiagnostically to improve cognition. However, more recently, studies using working memory training packages have targeted emotion-regulation outcomes to determine whether far transfer effects can be achieved. A narrative review is conducted of studies that have used standardized computerized working memory training packages across healthy volunteers, affect, anxiety, post-traumatic stress disorder (PTSD), and eating disordered populations with emotion-regulation outcomes. Working memory training has been used in children, adolescents, and adults to improve emotion regulation. Many studies have reported gains in mood as well as emotion-regulation strategies following working memory training, regardless of clinical indication and whether near transfer gains were achieved in cognitive domains. Significant emotion-regulation outcomes include: state and trait anxiety, rumination, brooding, positive appraisal, decreasing maladaptive emotion-regulation strategies, and decreasing intrusive thoughts. It is speculated that these far transfer outcomes from working memory training are possible due to the cognitive and neural overlap between cognitive and affective working memory, and emotion regulation. Working memory training could improve cognitive efficiency, which, in turn, increases the availability of cognitive resources during times when emotion regulation is taxed. Future studies need to consider the role of participant expectancy in predicting outcome measure performance, and including subjective and objective outcomes is paramount to study design. Furthermore, sample sizes require additional attention, given that the current review highlights that individual differences in non-clinical and clinical populations influence the outcomes from working memory training. Working memory training offers a possibility for improving emotion regulation transdiagnostically.

Receptor and circuit mechanisms underlying differential procognitive actions of psychostimulants

Psychostimulants, including methylphenidate (MPH), improve cognitive processes dependent on the prefrontal cortex (PFC) and extended frontostriatal circuitry. In both humans and animals, systemic MPH improves certain cognitive processes, such as working memory, in a narrow inverted-U-shaped manner. In contrast, other processes, including attention-related, are improved over a broader/right-shifted dose range. The current studies sought to elucidate the potential circuit and receptor mechanisms underlying the divergent dose-dependent procognitive effects of psychostimulants. We first observed that, as with working memory, although sustained attention testing was highly dependent on multiple frontostriatal regions, only MPH infusion into the dorsomedial PFC improved task performance. Importantly, the dose-response curve for this action was right-shifted relative to working memory, as seen with systemic administration. Additional studies examined the receptor mechanisms within the PFC associated with the procognitive actions of MPH across working memory and sustained attention tasks. We observed that PFC α2 and D1 receptors contributed to the beneficial effects of MPH across both cognitive tasks. However, α1 receptors only contributed to MPH-induced improvement in sustained attention. Moreover, activation of PFC α1 receptors was sufficient to improve sustained attention. This latter action contrasts with the impairing actions of PFC α1 receptors reported previously for working memory. These results provide further evidence for a prominent role of the PFC in the procognitive actions of MPH and demonstrate the divergent dose sensitivity across cognitive processes aligns with the differential involvement of PFC α1 receptors.

Methylphenidate increases willingness to perform effort in adults with ADHD

BACKGROUND

A reduced willingness to perform effort based on the magnitude and probability of potential rewards has been associated with diminished dopamine function and may be relevant to attention-deficit/hyperactivity disorder (ADHD). Here, we investigated the influence of ADHD status and methylphenidate on effort-based decisions. We hypothesized that ADHD participants would make fewer high-effort selections than non-ADHD subjects, and that methylphenidate would increase the number of high-effort selections. Furthermore, we hypothesized there would be associations among ADHD severity and methylphenidate-related changes in effort-based and attentional performance across all participants.

METHODS AND PARTICIPANTS

ADHD (n = 23) and non-ADHD (n = 23) adults completed the Effort Expenditure for Rewards Task in which participants select between low-effort and high-effort options to receive monetary rewards at varying levels of reward magnitude and probability. A test of attentional performance was also completed.

RESULTS

Overall, participants made more high-effort selections as potential reward magnitude and probability increased. ADHD participants did not make fewer high-effort selections than non-ADHD participants, but ADHD participants showed greater methylphenidate-related increases in high-effort selections. ADHD participants had worse attentional performance than non-ADHD participants. ADHD severity was associated with methylphenidate-related changes in high-effort selections, but not changes in attentional performance.

CONCLUSIONS

These results indicate that methylphenidate increases the willingness to perform effort in individuals with ADHD, possibly due to disorder-related motivational deficits. This provides support for theories of insufficient effort allocation among individuals with ADHD.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier, NCT02630017.

Neurocognitive, Autonomic, and Mood Effects of Adderall: A Pilot Study of Healthy College Students

Prescription stimulant medications are considered a safe and long-term effective treatment for Attention Deficit Hyperactivity Disorder (ADHD). Studies support that stimulants enhance attention, memory, self-regulation and executive function in individuals with ADHD. Recent research, however, has found that many college students without ADHD report misusing prescription stimulants, primarily to enhance their cognitive abilities. This practice raises the question whether stimulants actually enhance cognitive functioning in college students without ADHD. We investigated the effects of mixed-salts amphetamine (i.e., Adderall, 30 mg) on cognitive, autonomic and emotional functioning in a pilot sample of healthy college students without ADHD (n = 13), using a double-blind, placebo-controlled, within-subjects design. The present study was the first to explore cognitive effects in conjunction with mood, autonomic effects, and self-perceptions of cognitive enhancement. Results revealed that Adderall had minimal, but mixed, effects on cognitive processes relevant to neurocognitive enhancement (small effects), and substantial effects on autonomic responses, subjective drug experiences, and positive states of activated emotion (large effects). Overall, the present findings indicate dissociation between the effects of Adderall on activation and neurocognition, and more importantly, contrary to common belief, Adderall had little impact on neurocognitive performance in healthy college students. Given the pilot design of the study and small sample size these findings should be interpreted cautiously. The results have implications for future studies and the education of healthy college students and adults who commonly use Adderall to enhance neurocognition.