What are the cognitive effects of stimulant medications? Emphasis on adults with attention-deficit/hyperactivity disorder (ADHD)

Stimulant Drugs and Stimulant Use Disorder

The authors aim to summarize several key points of stimulant drugs and stimulant use disorder, including their indications, short-term and long-term adverse effects, current treatment strategies, and association with opioid medications. The global prevalence of stimulant use has seen annual increase in the last decade. Multiple studies have shown that stimulant use and stimulant use disorder are associated with a range of individual and public health issues. Stimulant misuse has led to a significant increase of overdose deaths in the United States.

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.

Is practice good enough? Retrieval benefits students with ADHD but does not compensate for poor encoding in unmedicated students

Introduction

A significant proportion of currently enrolled college students receive support for attention deficit/hyperactivity disorder (ADHD) and these students are often at risk of academic failure. Retrieval practice or self-testing is an effective, accessible, and affordable tool for improving academic performance. Three recent studies found conflicting results with regards to the effectiveness of retrieval practice in this population.

Methods

The present study compared 36 individuals with ADHD to 36 controls. Participants studied Swahili-English word pairs that varied in difficulty. Half of the pairs were repeatedly studied, and the other half repeatedly tested.

Results

On a final test, all participants showed a benefit of retrieval practice relative to restudy and participant status did not moderate the effect. However, unmedicated individuals with ADHD performed worse overall, both during the encoding phase and on the final test, whereas medicated participants were not significantly different from controls.

Discussion

An examination of self-reported encoding strategies found unmedicated participants used fewer deep strategies at encoding, consistent with prior work on ADHD and memory. Although retrieval practice is effective in this group, improved strategy use may be necessary to ensure performance that is fully equivalent to that of students without ADHD.

Prescription Stimulant Misuse Among Nursing Students: A Systematic Review

ABSTRACT

Nonmedical prescription stimulants are used to reduce symptoms of inattention, impulsivity, and hyperactivity in children and adults with attention-deficit hyperactivity/disorder. They are Schedule II controlled substances because of their high potential for dependence, and individuals who misuse them without a valid prescription are subject to criminal charges. Stimulant medications are also associated with common side effects (e.g., insomnia) as well as more serious but less common side effects (e.g., arrhythmias). Despite the potential health and legal consequences, misuse of prescription stimulants has become a public health crisis on college campuses in the United States. Neurocognitive enhancement is the primary reason that college students report misusing prescription stimulants, despite no enhancement of cognitive functioning when taken by healthy adults. Nursing students may be at risk for misuse because of their high levels of academic and clinical demands and because many start misusing in nursing school. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, the databases PubMed, Science Direct, EBSCOhost, and Academic OneFile were systematically searched to investigate the (a) percentage of prescription stimulant misuse studies that have included nursing students, (b) prevalence of prescription stimulant misuse among nursing students, (c) motivations for prescription stimulant misuse among nursing students, and (d) demographic factors associated with increased use among nursing students. Results revealed that of the 197 studies conducted within the past decade (2010-2021), only 1.02% (two) included nursing students. Future studies must investigate the prevalence and nature of prescription stimulant misuse among nursing students.

Theta power and functional connectivity as neurophysiological markers of executive functions in individuals with cognitive complaints in daily life

Impairments in executive functions (EFs) are common across psychological disorders. Research into the neural oscillations underlying EFs has the potential to help understand these impairments and contribute to the development of interventions. The aim of this study is to assess theta power and functional theta connectivity in the sensor space of the regions of the superordinate network for the core EFs: conflict monitoring, response inhibition, set-shifting, and working memory updating. We recruited adults with self-reported everyday EFs complaints and formed two groups: one with attention deficit hyperactivity disorder (ADHD) (n=27) and another without any diagnosis (n=22), and compared them to controls (n=21) on the Stroop, Stop-signal, Switching, and N-back task using EEG. Power and functional connectivity analyses were conducted for four regions of interest: frontal-midline, frontolateral left and right, and parietal region. For all four EFs, the groups showed a dynamical increase in theta power over time in the four regions of interest, as well as in functional theta connectivity between these regions. Group differences were found especially for conflict monitoring, with differences in theta power in the frontal-midline and frontolateral right region. These neural markers are also associated with behavioural performance and complaints in daily life. For set-shifting, group differences were less pronounced and for response inhibition and working memory updating no group differences were observed.

Malingering and Stimulant Medications Abuse, Misuse and Diversion

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that interferes with multiple aspects of daily functioning. Malingering or feigning of symptoms can be a major challenge during ADHD assessment. Stimulant medication abuse, misuse and diversion may constitute another challenge during management. A literature search of the past 15 years on the topic continued to suggest that there are several reasons for malingering and faking ADHD symptoms. Some of the reasons include the intent to obtain prescriptions for stimulant medications for performance enhancement, to gain access to additional school services and accommodations, to use recreationally and to sell as a street drug. In some countries, patients may receive additional tax or student loan benefits. Several researchers suggested that self-report rating measures are easily simulated by patients without ADHD. They concluded that no questionnaire has proved sufficiently robust against false positives. Some clinical factors that may suggest malingering during the ADHD assessment are highlighted and some available tests to detect malingering are discussed.

Human behavioral pharmacology of stimulant drugs: An update and narrative review

Stimulant use disorders present an enduring public health concern. Chronic stimulant use is associated with a range of health problems, with notable increases in stimulant overdose that disproportionately affect marginalized populations. With these persistent problems, it is important to understand the behavioral and pharmacological factors that contribute to stimulant use in humans. The purpose of this chapter is to provide an update and narrative review on recent human laboratory research that has evaluated the behavioral pharmacology of stimulant drugs. We focus on two prototypic stimulants: cocaine as a prototype monoamine reuptake inhibitor and d-amphetamine as a prototype monoamine releaser. As such, placebo controlled human laboratory studies that involved administration of doses of cocaine or d-amphetamine and were published in peer reviewed journals within the last 10 years (i.e., since 2011) are reviewed. Primary outcomes from these studies are subjective effects, reinforcing effects, cognitive/behavioral effects, and discriminative stimulus effects. Both cocaine and d-amphetamine produce classical stimulant-like behavioral effects (e.g., increase positive subjective effects, function as reinforcers), but there are notable gaps in the literature including understanding sex differences in response to stimulant drugs, cognitive-behavioral effects of stimulants, and influence of use history (e.g., relatively drug naïve vs drug experienced) on stimulant effects.

The effects of psychostimulants on cognitive functions in individuals with attention-deficit hyperactivity disorder: A systematic review

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is associated with a broad range of deficits in cognitive functions which has significant implications for quality of life. Psychostimulants are demonstrated to improve symptoms of inattention and hyperactivity/impulsivity, however, their impact on cognition remains incompletely characterized. Herein, the aim of this systematic review is to synthesize the extant literature reporting on the effects of psychostimulants on cognitive function in individuals with ADHD.

METHOD

A systematic search of PubMed, Scopus, and Web of Science from inception to July 2021 was conducted. Additional studies were identified through Google Scholar and a manual search of the reference lists of relevant articles. Inclusion criteria were original studies that evaluated the cognitive function of individuals with ADHD taking psychostimulants drugs. We assessed the quality of the included papers using the Newcastle-Ottawa scale (NOS).

RESULTS

A total of 10 studies involving 753 subjects with ADHD and 194 healthy controls were identified and eligible for inclusion. Nine studies evaluated the impact of methylphenidate on cognitive function and one study investigated the use of lisdexamfetamine. Results indicated that attentional deficits such as memory, vigilance, divided attention, phasic and tonic alertness, and focused attention were improved in ADHD patients treated with psychostimulants. The efficacy of psychostimulants in improving other domains of cognition remains inconclusive due to conflicting evidence or insignificant findings (ie. academic performance and executive function). Overall, results indicate that psychostimulants may improve only select domains of cognition (ie. memory and attention).

CONCLUSION

Psychostimulants are reported to improve several disparate aspects of cognition among individuals with ADHD. Further research is needed to better understand the complex relationships between cognition and behavior in ADHD, as well as the impact of medication on these distinct aspects of functioning. Further research is also needed to determine whether the pro-cognitive effect of stimulants would be transferable to other mental disorders.

Social and Economic Costs of Attention-Deficit/Hyperactivity Disorder Across the Lifespan

OBJECTIVE

To determine the financial and non-financial costs of Attention-Deficit/Hyperactivity Disorder (ADHD) across the lifespan.

METHOD

The population costs of ADHD in Australia were estimated for the financial year 2018 to 2019 using a prevalence approach to cost estimation across all ages. Financial (healthcare, productivity, education and justice systems, and deadweight losses) and non-financial costs were measured (Disability Adjusted Life Years (DALYs)).

RESULTS

The total social and economic cost of ADHD in 2018 to 2019 were US$12.76 billion (range US$8.40 billion to US$17.44 billion, with per person costs of US$15,664 per year). Productivity costs made up 81% of the total financial costs, followed by deadweight losses (11%), and health system costs (4%). Loss in terms of wellbeing was significant (US$5.31 billion).

CONCLUSION

There is a need to raise public awareness of the considerable socioeconomic impact and burden of ADHD in order to drive investment and policy decisions that improve identification and treatment of ADHD.

Academic Trajectories of College Students with and without ADHD: Predictors of Four-Year Outcomes

Objective: Completing a college degree is associated with success in employment, financial earnings, and life satisfaction. Mental health difficulties, including attention-deficit/hyperactivity disorder (ADHD), can compromise degree completion.Method: We examined 4-year academic performance trajectories of 201 college students with ADHD (97 receiving medication [ADHD-Med], 104 not receiving medication [ADHD-NoMed]) relative to 205 non-ADHD Comparison students. Demographic (e.g., sex, race/ethnicity), psychological (e.g., self-reported depression and anxiety symptoms), and service-related (e.g., receipt of academic support) variables were included as predictors of intercept (i.e., Year 1 performance) and slope (yearly change) of semester GPA, progress toward graduation, and self-reported study skill strategies.Results: College students with ADHD obtained significantly lower GPAs (Hedge's g = -0.46 and -0.63) and reported less frequent use of study skills strategies (Hedge's g range from -1.00 to -2.28) than Comparison students. Significantly more Comparison students (59.1%) persisted through eight semesters relative to ADHD-NoMed students (49%). Multiple variables predicted outcomes with parent education, fewer depressive symptoms, better executive functioning, and receipt of high school Section 504 accommodations and college academic support services among the strongest predictors.Conclusions: Findings suggest support services for students with ADHD should begin prior to college matriculation and focus on improving executive functioning skills and depressive symptoms to increase chances of academic success.

Novel Phenethylamines and Their Potential Interactions With Prescription Drugs: A Systematic Critical Review

BACKGROUND

The novel phenethylamines 4-fluoroamphetamine (4-FA) and 2,5-dimethoxy-4-bromophenethylamine (2C-B) fall in the top 10 most used new psychoactive substances (NPSs) among high-risk substance users. Various phenethylamines and NPS are also highly used in populations with mental disorders, depression, or attention deficit hyperactivity disorder (ADHD). Moreover, NPS use is highly prevalent among men and women with risky sexual behavior. Considering these specific populations and their frequent concurrent use of drugs, such as antidepressants, ADHD medication, and antiretrovirals, reports on potential interactions between these drugs, and phenethylamines 4-FA and 2C-B, were reviewed.

METHODS

The authors performed a systematic literature review on 4-FA and 2C-B interactions with antidepressants (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, duloxetine, bupropion, venlafaxine, phenelzine, moclobemide, and tranylcypromine), ADHD medications (atomoxetine, dexamphetamine, methylphenidate, and modafinil), and antiretrovirals.

RESULTS

Limited literature exists on the pharmacokinetics and drug-drug interactions of 2C-B and 4-FA. Only one case report indicated a possible interaction between 4-FA and ADHD medication. Although pharmacokinetic interactions between 4-FA and prescription drugs remain speculative, their pharmacodynamic points toward interactions between 4-FA and ADHD medication and antidepressants. The pharmacokinetic and pharmacodynamic profile of 2C-B also points toward such interactions, between 2C-B and prescription drugs such as antidepressants and ADHD medication.

CONCLUSIONS

A drug-drug (phenethylamine-prescription drug) interaction potential is anticipated, mainly involving monoamine oxidases for 2C-B and 4-FA, with monoamine transporters being more specific to 4-FA.

The Use and Impact of Cognitive Enhancers among University Students: A Systematic Review

INTRODUCTION

Cognitive enhancers (CEs), also known as "smart drugs", "study aids" or "nootropics" are a cause of concern. Recent research studies investigated the use of CEs being taken as study aids by university students. This manuscript provides an overview of popular CEs, focusing on a range of drugs/substances (e.g., prescription CEs including amphetamine salt mixtures, methylphenidate, modafinil and piracetam; and non-prescription CEs including caffeine, cobalamin (vitamin B12), guarana, pyridoxine (vitamin B6) and vinpocetine) that have emerged as being misused. The diverted non-prescription use of these molecules and the related potential for dependence and/or addiction is being reported. It has been demonstrated that healthy students (i.e., those without any diagnosed mental disorders) are increasingly using drugs such as methylphenidate, a mixture of dextroamphetamine/amphetamine, and modafinil, for the purpose of increasing their alertness, concentration or memory.

AIM

To investigate the level of knowledge, perception and impact of the use of a range of CEs within Higher Education Institutions.

METHODOLOGY

A systematic review was conducted in adherence with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Whilst 1400 studies were identified within this study through a variety of electronic databases (e.g., 520 through PubMed, 490 through Science Direct and 390 through Scopus), 48 papers were deemed relevant and were included in this review.

RESULTS

The most popular molecules identified here included the stimulant CEs, e.g., methylphenidate, modafinil, amphetamine salt mixtures and caffeine-related compounds; stimulant CEs' intake was more prevalent among males than females; drugs were largely obtained from friends and family, as well as via the Internet. It is therefore suggested that CEs are increasingly being used among healthy individuals, mainly students without any diagnosed cognitive disorders, to increase their alertness, concentration, or memory, in the belief that these CEs will improve their performance during examinations or when studying. The impact of stimulant CEs may include tolerance, dependence and/or somatic (e.g., cardiovascular; neurological) complications.

DISCUSSION

The availability of CEs for non-medical indications in different countries is influenced by a range of factors including legal, social and ethical factors. Considering the risk factors and motivations that encourage university students to use CE drugs, it is essential to raise awareness about CE-related harms, counteract myths regarding "safe" CE use and address cognitive enhancement in an early stage during education as a preventative public health measure.

Non-credible symptom report in the clinical evaluation of adult ADHD: development and initial validation of a new validity index embedded in the Conners' adult ADHD rating scales

As attention-deficit/hyperactivity disorder (ADHD) is a feasible target for individuals aiming to procure stimulant medication or accommodations, there is a high clinical need for accurate assessment of adult ADHD. Proven falsifiability of commonly used diagnostic instruments is therefore of concern. The present study aimed to develop a new, ADHD-specific infrequency index to aid the detection of non-credible self-report. Disorder-specific adaptations of four detection strategies were embedded into the Conners’ Adult ADHD Rating Scales (CAARS) and tested for infrequency among credible neurotypical controls (n = 1001) and credible adults with ADHD (n = 100). The new index’ ability to detect instructed simulators (n = 242) and non-credible adults with ADHD (n = 22) was subsequently examined using ROC analyses. Applying a conservative cut-off score, the new index identified 30% of participants instructed to simulate ADHD while retaining a specificity of 98%. Items assessing supposed symptoms of ADHD proved most useful in distinguishing genuine patients with ADHD from simulators, whereas inquiries into unusual symptom combinations produced a small effect. The CAARS Infrequency Index (CII) outperformed the new infrequency index in terms of sensitivity (46%), but not overall classification accuracy as determined in ROC analyses. Neither the new infrequency index nor the CII detected non-credible adults diagnosed with ADHD with adequate accuracy. In contrast, both infrequency indices showed high classification accuracy when used to detect symptom over-report. Findings support the new indices’ utility as an adjunct measure in uncovering feigned ADHD, while underscoring the need to differentiate general over-reporting from specific forms of feigning.

Shifting uncertainty intolerance: methylphenidate and attention-deficit hyperactivity disorder

Risk evaluation is a critical component of decision making. Risk tolerance is relevant in both daily decisions and pathological disorders such as attention-deficit hyperactivity disorder (ADHD), where impulsivity is a cardinal symptom. Methylphenidate, a commonly prescribed drug in ADHD, improves attention but has mixed reports on risk-based decision making. Using a double-blinded placebo protocol, we studied the risk attitudes of ADHD patients and age-matched healthy volunteers while performing the 2-step sequential learning task and examined the effect of methylphenidate on their choices. We then applied a novel computational analysis using the hierarchical drift-diffusion model to extract parameters such as threshold ('a'-amount of evidence accumulated before making a decision), drift rate ('v'-information processing speed) and response bias ('z' apriori bias towards a specific choice) focusing specifically on risky choice preference. Critically, we show that ADHD patients on placebo have an apriori bias towards risky choices compared to controls. Furthermore, methylphenidate enhanced preference towards risky choices (higher apriori bias) in both groups but had a significantly greater effect in the patient population independent of clinical scores. Thus, methylphenidate appears to shift tolerance towards risky uncertain choices possibly mediated by prefrontal dopaminergic and noradrenergic modulation. We emphasise the utility of computational models in detecting underlying processes. Our findings have implications for subtle yet differential effects of methylphenidate on ADHD compared to healthy population.

A novel approach to intra-individual performance variability in ADHD

Patients with attention deficit/(hyperactivity) disorder (AD(H)D) show increased intra-individual variability (IIV) in behavioral performance. This likely reflects dopaminergic deficiencies. However, the precise performance profile across time and the pattern of fluctuations within it have not yet been considered, partly due to insufficient methods. Yet, such an analysis may yield important theory-based implications for clinical practice. Thus, in a case-control cross-sectional study, we introduce a new method to investigate performance fluctuations in patients with ADD (n = 76) and ADHD (n = 67) compared to healthy controls (n = 45) in a time estimation task. In addition, we also evaluate the effects of methylphenidate (MPH) treatment on this performance pattern in 29 patients with AD(H)D. Trial-by-trial differences in performance between healthy controls and patients with AD(H)D do not persist continuously over longer time periods. Periods during which no differences in performance between healthy controls and patients occur alternate with periods in which such differences are present. AD(H)D subtype and surprisingly also medication status does not affect this pattern. The presented findings likely reflect (phasic) deficiencies of the dopaminergic system in patients with AD(H)D which are not sufficiently ameliorated by first-line pharmacological treatment. The presented findings carry important clinical and scientific implications.

Methylphenidate for attention problems in epilepsy patients: Safety and efficacy

Children with attention deficit hyperactivity disorder (ADHD) have an increased risk of seizures, and children with epilepsy have an increased prevalence of ADHD. Adults with epilepsy often have varying degrees of attentional dysfunction due to multiple factors, including anti-seizure medications, frequent seizures, interictal discharges, underlying lesions, and psychiatric comorbidities. Currently, there are no approved medications for the treatment of epilepsy-related attentional dysfunction. Methylphenidate (MPH) is a stimulant, FDA-approved for the treatment of ADHD, and often used for ADHD in the setting of pediatric epilepsy. Large database and registry studies indicate safety of MPH in children with ADHD and epilepsy, with no significant effect on seizure frequency. Small single-dose and open-label studies suggest efficacy of MPH in adults with epilepsy-related attention deficits. Methylphenidate represents a possible treatment for attentional dysfunction due to epilepsy, but large, randomized, placebo-controlled, double-blinded studies are needed.

Visual statistical learning and integration of perceptual priors are intact in attention deficit hyperactivity disorder

Background

Deficits in visual statistical learning and predictive processing could in principle explain the key characteristics of inattention and distractibility in attention deficit hyperactivity disorder (ADHD). Specifically, from a Bayesian perspective, ADHD may be associated with flatter likelihoods (increased sensory processing noise), and/or difficulties in generating or using predictions. To our knowledge, such hypotheses have never been directly tested.

Methods

We here test these hypotheses by evaluating whether adults diagnosed with ADHD (n = 17) differed from a control group (n = 30) in implicitly learning and using low-level perceptual priors to guide sensory processing. We used a visual statistical learning task in which participants had to estimate the direction of a cloud of coherently moving dots. Unbeknown to the participants, two of the directions were more frequently presented than the others, creating an implicit bias (prior) towards those directions. This task had previously revealed differences in other neurodevelopmental disorders, such as autistic spectrum disorder and schizophrenia.

Results

We found that both groups acquired the prior expectation for the most frequent directions and that these expectations substantially influenced task performance. Overall, there were no group differences in how much the priors influenced performance. However, subtle group differences were found in the influence of the prior over time.

Conclusion

Our findings suggest that the symptoms of inattention and hyperactivity in ADHD do not stem from broad difficulties in developing and/or using low-level perceptual priors.

Creativity in ADHD: Goal-Directed Motivation and Domain Specificity

Objective: This research aimed to provide explanations for the inconsistent findings regarding creativity in ADHD. Method: In Study 1, we assessed real-world creative achievements and intrinsic motivation during idea generation in adults with ADHD and compared these with controls. In Study 2, we manipulated competition during idea generation to investigate effects on idea originality in adults with ADHD versus controls, and assessed creativity in specific domains. Results: Adults with ADHD reported more real-world creative achievements. We did not observe differences in intrinsic motivation during idea generation between groups, but adults with ADHD generated more original ideas when competing for a bonus. Moreover, adults with ADHD rated themselves as more creative in specific creative domains. Conclusion: Our findings suggest that goal-directed motivation may drive the enhanced real-world creative achievements of people with ADHD. Moreover, people with ADHD may selectively engage and excel in creative domains that fit their skills and preferences.

Objective Level of Alertness and Inhibitory Control Predict Highway Driving Impairment in Adults With ADHD

Objective: It remains unclear whether daytime impairments in ADHD patients are better explained by an altered level of alertness and/or by cognitive deficits. The aim of this study was to determine the respective contribution of these factors on driving performance in ADHD adults. Method: ADHD adults (n = 39) and healthy controls (n = 18) underwent a nocturnal polysomnography (PSG) followed by a Maintenance of Wakefulness Test (MWT), a simulated driving task, and a neuropsychological evaluation. Results: ADHD patients had shorter mean sleep latency on the MWT and worse driving performance than controls. They also made more errors on attention and executive functioning tests. Logistic regression analyses showed that inhibition deficits and objective daytime sleepiness predicted highway driving performance in ADHD. Conclusion: Our study shows that not only inhibitory control deficits but also pathological level of alertness independently contribute to highway driving impairment in ADHD patients, providing a better understanding of the pathophysiological mechanisms involved in ADHD.

Una aproximación bioética a la mejora cognitiva en individuos sanos

La discusión sobre el human enhancement es uno de los temas que ha tomado más relevancia dentro de los debates bioéticos actuales. En este artículo realizaremos un abordaje sobre este concepto, específicamente en relación al tema de la mejora cognitiva. Con la idea de crear un marco ético reflexivo, abordaremos el tema desde varias vertientes. En primer lugar, cómo se entiende la mejora cognitiva, a partir de dos aspectos distintos: la finalidad de la mejora y la acción mejoradora en sí misma. Posteriormente, se enfocarán los alcances de la mejora cognitiva desde la óptica de las investigaciones científicas sobre el tema. En la segunda parte del texto, analizaremos (a partir del meta-análisis de una selección de investigaciones científico-empíricas) el tema de si realmente se presenta una mejora y, de ser así, de qué clase de mejora se trata. Para finalizar, realizaremos una reflexión en torno a los problemas morales que presenta la mejora cognitiva, para concluir brevemente que este tipo de mejora solo se presenta en un sentido muy limitado, al tiempo que se encuentra justificada por un marco reduccionista de la cognición y, por lo tanto, del ser humano mismo.

ADHD 24/7: Circadian clock genes, chronotherapy and sleep/wake cycle insufficiencies in ADHD

Objectives: The current paper addresses the evidence for circadian clock characteristics associated with attention-deficit hyperactivity disorder (ADHD), and possible therapeutic approaches based on chronomodulation through bright light (BL) therapy.Methods: We review the data reported in ADHD on genetic risk factors for phase-delayed circadian rhythms and on the role of photic input in circadian re-alignment.Results: Single nucleotide polymorphisms in circadian genes were recently associated with core ADHD symptoms, increased evening-orientation and frequent sleep problems. Additionally, alterations in exposure and response to photic input may underlie circadian problems in ADHD. BL therapy was shown to be effective for re-alignment of circadian physiology toward morningness, reducing sleep disturbances and bringing overall improvement in ADHD symptoms. The susceptibility of the circadian system to phase shift by timed BL exposure may have broad cost-effective potential implications for the treatment of ADHD.Conclusions: We conclude that further research of circadian function in ADHD should focus on detection of genetic markers (e.g., using human skin fibroblasts) and development of BL-based therapeutic interventions.

Effects of Expectancy on Cognitive Performance, Mood, and Psychophysiology in Healthy Adolescents and Their Parents in an Experimental Study

OBJECTIVE

Placebo effects on cognitive performance and mood and their underlying mechanisms have rarely been investigated in adolescents. Therefore, the following hypotheses were investigated with an experimental paradigm: (1) placebo effects could be larger in adolescents than in adults, (2) parents' expectations influence their adolescents' expectations and placebo effects, and (3) a decrease in stress levels could be an underlying mechanism of placebo effects.

METHODS

Twenty-six healthy adolescents (13.8 ± 1.6 years, 14 girls) each with a parent (45.5 ± 4.2 years, 17 mothers) took part in an experimental within-subjects study. On two occasions, a transdermal patch was applied to their hips and they received an envelope containing either the information that it is a Ginkgo patch to improve cognitive performance and mood, or it is an inactive placebo patch, in counterbalanced order. Cognitive performance and mood were assessed with a parametric Go/No-Go task (PGNG), a modification of California Verbal Learning Test, and Profile of Mood Scales (POMS). Subjects rated their expectations about Ginkgo's effects before patch application as well as their subjective assessment of its effects after the tests. An electrocardiogram and skin conductance levels (SCLs) were recorded and root mean square of successive differences (RMSSD), high-frequency power (HF), and the area under the curve of the SCL (AUC) were analyzed as psychophysiological stress markers.

RESULTS

Expectations did not differ between adolescents and parents and were correlated concerning reaction times only. Overall, expectations did not influence placebo effects. There was only one significant placebo effect on the percentage of correct inhibited trials in one level of the PGNG in adolescents, but not in parents. RMSSD and HF significantly increased, and AUC decreased from pre- to post-patch application in adolescents, but not in parents.

CONCLUSION

With this experimental paradigm, we could not induce relevant placebo effects in adolescents and parents. This could be due to aspects of the study design such as application form and substance, and that healthy subjects were employed. Nevertheless, we could show that adolescents are more sensitive to psychophysiological reactions related with interventions which could be part of the underlying mechanisms of placebo effects in adolescents.

CK1δ over-expressing mice display ADHD-like behaviors, frontostriatal neuronal abnormalities and altered expressions of ADHD-candidate genes

The cognitive mechanisms underlying attention-deficit hyperactivity disorder (ADHD), a highly heritable disorder with an array of candidate genes and unclear genetic architecture, remain poorly understood. We previously demonstrated that mice overexpressing CK1δ (CK1δ OE) in the forebrain show hyperactivity and ADHD-like pharmacological responses to D-amphetamine. Here, we demonstrate that CK1δ OE mice exhibit impaired visual attention and a lack of D-amphetamine-induced place preference, indicating a disruption of the dopamine-dependent reward pathway. We also demonstrate the presence of abnormalities in the frontostriatal circuitry, differences in synaptic ultra-structures by electron microscopy, as well as electrophysiological perturbations of both glutamatergic and GABAergic transmission, as observed by altered frequency and amplitude of mEPSCs and mIPSCs. Furthermore, gene expression profiling by next-generation sequencing alone, or in combination with bacTRAP technology to study specifically Drd1a versus Drd2 medium spiny neurons, revealed that developmental CK1δ OE alters transcriptional homeostasis in the striatum, including specific alterations in Drd1a versus Drd2 neurons. These results led us to perform a fine molecular characterization of targeted gene networks and pathway analysis. Importantly, a large fraction of 92 genes identified by GWAS studies as associated with ADHD in humans are significantly altered in our mouse model. The multiple abnormalities described here might be responsible for synaptic alterations and lead to complex behavioral abnormalities. Collectively, CK1δ OE mice share characteristics typically associated with ADHD and should represent a valuable model to investigate the disease in vivo.

Association of ADHD medications with the risk of cardiovascular diseases: a meta-analysis

This meta-analysis was conducted to evaluate the association between Attention deficit hyperactivity disorder (ADHD) medications and risk of sudden death/arrhythmia, stroke, myocardial infarction as well as all-cause death. We searched PubMed, Web of Science and China National Knowledge Infrastructure from 1950 to May 2018. All observational studies that the exposure of interest was ADHD medications, the outcome of interest was sudden death/arrhythmia, stroke, myocardial infarction as well as all-cause death, and the study reported relative risks (RRs) with 95% confidence intervals (95% CIs) were included. Pooled RRs were estimated by random-effects model. Subgroup analyses were conducted to examine the effects of study design, population, Country, follow-up duration, female proportion, covariates adjustment on the risk of sudden death/arrhythmia. Eight articles with ten studies (4,221,929 participants) were included in this meta-analysis about the association between ADHD medications and risk of sudden death/arrhythmia. The pooled RRs with 95% CIs of sudden death/arrhythmia for ADHD medications were 1.39 (1.06, 1.83). The result of the cohort study was 1.24 (0.84, 1.83). The pooled RRs between ADHD medications and stroke, myocardial infarction, all-cause death were 1.00 (0.74, 1.35), 0.91 (0.79, 1.05), 0.89 (0.54, 1.45), respectively. As for methylphenidate, the pooled RRs between methylphenidate and sudden death/arrhythmia, stroke, myocardial infarction, all-cause death were 1.46 (1.03, 2.07), 0.92 (0.70, 1.21), 0.97 (0.77, 1.23), 1.00 (0.49, 2.04), respectively. Based on the results of cohort studies, there was no correlation between ADHD medications and sudden death/arrhythmia, stroke, myocardial infarction and all-cause death. However, some of the confidence intervals do not exclude modest elevated risks, e.g., for sudden death/arrhythmia.

Gender and hand dominance on fine motor skills among Grade 1–7 learners with attention-deficit hyperactivity disorder

Children diagnosed with attention-deficit/hyperactivity disorder encounter difficulties in many activities in their daily lives that require motor coordination skills. The aim of this study was to establish whether children with attention-deficit/hyperactivity disorder have deficits in fine motor skills. Eighty male and female learners diagnosed with attention-deficit/hyperactivity disorder matched with 80 non-attention-deficit/hyperactivity disorder from the North West and Limpopo provinces (South Africa), aged 7–13  years, participated in the study. All participants completed the grooved pegboard test, the maze coordination task, and the finger tapping test. These instruments measure various functions of motor speed and eye–hand coordination. The findings reveal that children with attention-deficit/hyperactivity disorder performed significantly poorer than the control group with regard to the grooved pegboard and maze coordination tasks, but not with the finger tapping task. There were no gender differences in all the tests. Performance on the maze coordination task with the non-dominant hand was poorer for the attention-deficit/hyperactivity disorder group with regard to the time taken to complete the task. However, no hand dominance differences were found on the grooved pegboard and finger tapping tests. The study revealed a relationship between attention-deficit/hyperactivity disorder symptomatology and motor problems with regard to complex tasks of accuracy, but not on a simple task of motor speed. It is, therefore, recommended that since children with attention-deficit/hyperactivity disorder show motor deficiencies, motor skill training should be considered as part of the intervention, as these skills are needed for many daily activities and academic competencies.

Efficacy and safety of naltrexone for amfetamine and methamfetamine use disorder: a systematic review of randomized controlled trials

INTRODUCTION

Amfetamine and methamfetamine abuse remains a prevalent health problem, increasing the burden on healthcare. Naltrexone, a µ-opioid receptor antagonist, has been suggested as a promising treatment for amfetamine and methamfetamine use disorder.

OBJECTIVE

To review the current evidence for the efficacy and safety of naltrexone as a pharmacological treatment for amfetamine and methamfetamine use disorder. The primary outcome was defined as abstinence or reduction of use. Secondary outcomes were, attenuated "positive" subjective effects (e.g., "feel good," "craving," etc.) of amfetamine or methamfetamine after naltrexone treatment, adverse events and physiological changes (e.g., blood pressure, heart rate).

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A systematic literature search was conducted on 2 April 2017, and updated on 31 March 2018. Records were retrieved from databases including PubMed, EMBASE Classic plus EMBASE 1980 via Ovid, and the databases were searched using keywords and/or headings: (naltrexone AND amfetamine AND dependence) OR (naltrexone AND amfetamine AND craving) OR (vivitrol AND amfetamine) OR (revia AND amfetamine) OR (naltrexone AND amfetamine) OR (naltrexone AND methamfetamine dependence) OR (naltrexone AND methamfetamine AND craving) OR (vivitrol AND methamfetamine) OR (revia AND methamfetamine) OR (naltrexone AND ice) OR (naltrexone AND crystal meth) OR (naltrexone AND methamfetamine). Studies investigating the effects of naltrexone on amfetamine or methamfetamine use were eligible for inclusion. All studies were rated as low risk of bias using the Cochrane tool for risk of bias.

RESULTS

Among 591 identified studies, there were four randomized controlled trials. Two studies investigated the effects of naltrexone on amfetamine use disorder and two on methamfetamine use. Compared to placebo, the abstinence rate was increased significantly (p < 0.05) by naltrexone in one of two amfetamine studies, whereas there was no statistical difference in the only study reporting methamfetamine use. In one out of two amfetamine studies, naltrexone significantly attenuated either craving levels or subjective effects (e.g., "want more," "like effect") relative to placebo (p < 0.05). Additionally, only in one of two methamfetamine studies did naltrexone produce a significant reduction (p < 0.05) in craving levels or attenuated subjective effects. Both amfetamine and methamfetamine studies showed good tolerability of naltrexone, with few adverse events seen.

CONCLUSIONS

There is presently insufficient evidence to support the use of naltrexone in amfetamine and metamfetamine use disorders. There is a compelling need for high-quality studies to further evaluate the potential use of naltrexone.

Effect of an Ecological Executive Skill Training Program for School-aged Children with Attention Deficit Hyperactivity Disorder: A Randomized Controlled Clinical Trial

Background:

As medication does not normalize outcomes of children with attention deficit hyperactivity disorder (ADHD), especially in real-life functioning, nonpharmacological methods are important to target this field. This randomized controlled clinical trial was designed to evaluate the effects of a comprehensive executive skill training program for school-aged children with ADHD in a relatively large sample.

Methods:

The children (aged 6–12 years) with ADHD were randomized to the intervention or waitlist groups. A healthy control group was composed of gender- and age-matched healthy children. The intervention group received a 12-session training program for multiple executive skills. Executive function (EF), ADHD symptoms, and social functioning in the intervention and waitlist groups were evaluated at baseline and the end of the final training session. The healthy controls (HCs) were only assessed once at baseline. Repeated measures analyses of variance were used to compare EF, ADHD symptoms, and social function between intervention and waitlist groups.

Results:

Thirty-eight children with ADHD in intervention group, 30 in waitlist group, and 23 healthy children in healthy control group were included in final analysis. At posttreatment, intervention group showed significantly lower Behavior Rating Inventory of Executive Function (BRIEF) total score (135.89 ± 16.80 vs. 146.09 ± 23.92, P = 0.04) and monitoring score (18.05 ± 2.67 vs. 19.77 ± 3.10, P = 0.02), ADHD-IV overall score (41.11 ± 7.48 vs. 47.20 ± 8.47, P < 0.01), hyperactivity-impulsivity (HI) subscale score (18.92 ± 5.09 vs. 21.93 ± 4.93, P = 0.02), and inattentive subscale score (22.18 ± 3.56 vs. 25.27 ± 5.06, P < 0.01), compared with the waitlist group. Repeated measures analyses of variance revealed significant interactions between time and group on the BRIEF inhibition subscale (F = 5.06, P = 0.03), working memory (F = 4.48, P = 0.04), ADHD-IV overall score (F = 21.72, P < 0.01), HI subscale score (F = 19.08, P < 0.01), and inattentive subscale score (F = 12.40, P < 0.01). Multiple-way analysis of variance showed significant differences on all variables of BRIEF, ADHD-rating scale-IV, and WEISS Functional Impairment Scale-Parent form (WFIRS-P) among the intervention and waitlist groups at posttreatment and HCs at baseline.

Conclusions:

This randomized controlled study on executive skill training in a relatively large sample provided some evidences that the training could improve EF deficits, reduce problematic symptoms, and potentially enhance the social functioning in school-aged children with ADHD.

Clinical Trial Registration:

http://www.clinicaltrials.gov; NCT02327585.

Nonmedical prescription stimulant users experience subjective but not objective impairments in attention and impulsivity

BACKGROUND AND OBJECTIVES

Nonmedical prescription stimulant use is frequently reported by college students to improve academic performance, yet it is unknown whether users truly experience cognitive impairments that may drive use. This research compared students with at least one report of nonmedical prescription stimulant use and nonusers on both self-report and objective measures of inattention and impulsivity.

METHODS

Two studies examined inattention (N = 155) and impulsivity (N = 115) among college students. Participants completed self-report questionnaires and cognitive tests, including Digit Span, the Paced Auditory Serial Addition Test, and a Continuous Performance Test to assess inattention, and the Balloon Analogue Risk Task and the Stop Signal Task to assess risk-taking and impulsivity.

RESULTS

Self-reports of inattention and impulsive symptoms were significantly higher among users, controlling for gender, GPA, self-reported ADHD, alcohol use, and drug use; however, no objective differences were found.

DISCUSSION AND CONCLUSIONS

Nonmedical prescription stimulant users may engage in use to overcome perceived deficits in cognitive abilities despite lack of objective evidence.

SCIENTIFIC SIGNIFICANCE

Understanding discrepancies in objective performance and subjective reports may aid in the development of effective interventions for nonmedical prescription stimulant use. (Am J Addict 2018;27:238-244).

Amphetamine Modestly Improves Conners' Continuous Performance Test Performance in Healthy Adults

OBJECTIVES

Amphetamine improves vigilance as assessed by continuous performance tests (CPT) in children and adults with attention deficit hyperactivity disorder (ADHD). Less is known, however, regarding amphetamine effects on vigilance in healthy adults. Thus, it remains unclear whether amphetamine produces general enhancement of vigilance or if these effects are constrained to the remediation of deficits in patients with ADHD.

METHODS

We tested 69 healthy adults (35 female) on a standardized CPT (Conner's CPT-2) after receiving 10- or 20-mg d-amphetamine or placebo. To evaluate potential effects on learning, impulsivity, and perseveration, participants were additionally tested on the Iowa Gambling Task (IGT) and Wisconsin Card Sorting Task (WCST).

RESULTS

Participants receiving placebo exhibited the classic vigilance decrement, demonstrated by a significant reduction in attention (D') across the task. This vigilance decrement was not observed, however, after either dose of amphetamine. Consistent with enhanced vigilance, the 20-mg dose also reduced reaction time variability across the task and the ADHD confidence index. The effects of amphetamine appeared to be selective to vigilance since no effects were observed on the IGT, WCST, or response inhibition/perseveration measures from the CPT.

CONCLUSIONS

The present data support the premise that amphetamine improves vigilance irrespective of disease state. Given that amphetamine is a norepinephrine/dopamine transporter inhibitor and releaser, these effects are informative regarding the neurobiological substrates of attentional control. (JINS, 2018, 24, 283-293).

Social Policy and Cognitive Enhancement: Lessons from Chess

Should the development of pharmacological cognitive enhancers raise worries about doping in cognitively demanding activities? In this paper, we argue against using current evidence relating to enhancement to justify a ban on cognitive enhancers using the example of chess. It is a mistake to assume that enhanced cognitive functioning on psychometric testing is transferable to chess performance because cognitive expertise is highly complex and in large part not merely a function of the sum specific sub-processes. A deeper reason to doubt that pharmacological cognitive enhancers would be as significant in mind sports is the misleading parallel with physical enhancement. We will make the case that cognitive performance is less mechanical in nature than physical performance. We draw lessons from this case example of chess for the regulation of cognitive enhancement more generally in education and the professions. Premature regulation runs the risk of creating a detrimental culture of suspicion that ascribes unwarranted blame.

Perceived academic benefit is associated with nonmedical prescription stimulant use among college students

INTRODUCTION

College students are at higher than average risk for nonmedical use of prescription stimulants (NPS). A commonly identified motive among students who engage in NPS is to improve grades. Several research studies have observed that NPS most likely does not confer an academic advantage, and is associated with excessive drinking and other drug use. This study documents the proportion of the general college student population who believe that NPS will lead to improvements in academic performance.

METHODS

This study gathered online survey data from a large, demographically diverse sample of college students to document the prevalence of perceived academic benefit of NPS for improving grades and to examine the association between such belief and NPS.

RESULTS

Overall, 28.6% agreed or strongly agreed that NPS could help students earn higher grades, and an additional 38.0% were unsure. Students with a higher level of perceived academic benefit of NPS and more frequent patterns of drinking and marijuana use were more likely to engage in NPS, even after adjustment for a wide range of covariates.

CONCLUSIONS

The results underscore the need for interventions that simultaneously correct misperceptions related to academic benefit and target alcohol and marijuana use to reduce NPS.

Methylphenidate enhances implicit learning in healthy adults

BACKGROUND AND PURPOSE

One limiting factor in the development of pharmacological interventions to enhance cognition is the absence of biomarkers that can be used in healthy volunteers to screen novel compounds. Drug discovery has tended to rely heavily on explicit measures of cognition, but these are typically insensitive to cognition-enhancing effects in healthy volunteers. This study investigated whether a novel battery of implicit cognition measures is sensitive to the effects of methylphenidate (Ritalin) in healthy volunteers.

EXPERIMENTAL APPROACH

Eighty healthy volunteers were randomised to receive either a single (10 mg) dose of methylphenidate or matched placebo. Participants completed a battery of tasks measuring implicit cognition (location priming, contextual cueing, implicit task switching). The effect of methylphenidate on standard, explicit measures of cognition was also assessed.

KEY RESULTS

Methylphenidate enhanced implicit learning on the location priming task and the implicit task-switching task. In line with previous work, we found that these effects were greater in male volunteers. There was no evidence for improved learning in any of the explicit measures.

CONCLUSION AND IMPLICATIONS

These results demonstrate that implicit measures of cognition are sensitive to pharmacological interventions in healthy volunteers. As such, implicit cognition measures may be a useful way of screening and tracking cognitive effects of novel agents in experimental medicine studies.

Fractionating Executive Functions of Adults With ADHD

OBJECTIVE

To evaluate the performance of adults with ADHD considering the fractionation of executive functions into six different domains.

METHOD

Participants were adult ADHD patients who were not under the acute effects of medication ( n = 48). Their performance was compared with that of a healthy control group ( n = 20) of comparable age, education, and nonverbal intelligence quotient. The cognitive domains assessed were executive shifting, updating, inhibition of prepotent responses, dual-task performance, planning, and access to long-term memory. We also assessed the symptoms of inattention, hyperactivity/impulsivity, anxiety, and depression by validated questionnaires.

RESULTS

Compared with controls, patients reported more symptoms related to ADHD, anxiety and depression symptoms and were impaired in the shifting cost measure and phonemic fluency (measure of access to long-term memory).

CONCLUSION

ADHD in adults selectively impaired executive shifting and access to long-term memory, domains that may alter performance in a wide range of daily tasks.

Mixed-amphetamine salts expectancies among college students: Is stimulant induced cognitive enhancement a placebo effect?

INTRODUCTION

Non-medical use of prescription stimulants for cognitive enhancement in college students is increasing, despite evidence showing little benefit in non-clinical populations. The balanced placebo design (BPD) was used to independently evaluate the pharmacologic versus expectancy effects of mixed amphetamine salts on cognitive performance among a non-clinical sample of college-aged students.

METHOD

Participants were screened and excluded for ADHD and other psychopathologies. A non-clinical sample (N=32) completed four two-hour laboratory sessions and were administered a neurocognitive battery in each session. Medication Assignment (10mg mixed-amphetamine salt (Adderall™) versus placebo) was crossed with Instructional Set (deception versus truth). A within-subjects design was used, such that all participants experienced each of the four conditions of the BPD during one of the four laboratory sessions.

RESULTS

Participants performed no better than chance in identifying whether they received stimulant or placebo (Belief about Medication Assignment; 47% agreement; κ=-0.047, p=0.590). Participants showed improvement on only two of 31 subtests during active medication. Expecting and receiving stimulants was associated with improved cognitive performance. However, expecting placebo was associated with worse cognitive performance, regardless of the type of medication given.

DISCUSSION

This study demonstrated that although non-medical use of stimulants does not enhance cognition, expectancies prominently influence cognitive performance. Participants who believed they received active medication both subjectively rated themselves as performing better and objectively performed better on a minority of subtests, independent of medication state.

Memorable Messages about the Misuse of Prescription Stimulants

The misuse of prescription stimulants among college undergraduates is a prevalent and dangerous problem on college campuses across the United States. Guided by a memorable messages framework, this research sought to examine the messages that college students recall about the misuse of prescription stimulants and examine how those messages are associated with students' intention to use stimulants. We analyzed the recalled memorable messages of 129 undergraduates. Three predominant themes emerged from the analysis: academic implications, health implications, and ethical implications. Theme, source, and valence of the memorable messages were not associated with behavioral intention to engage in the misuse of prescription stimulants. These findings contribute to the scholarly and practical understanding of undergraduates' experiences with illicit behaviors, and demonstrate a need to further investigate students' sense-making in relation to risky decisions made during their college experience.

Linking ADHD to the Neural Circuitry of Attention

Attention deficit hyperactivity disorder (ADHD) is a complex condition with a heterogeneous presentation. Current diagnosis is primarily based on subjective experience and observer reports of behavioral symptoms - an approach that has significant limitations. Many studies show that individuals with ADHD exhibit poorer performance on cognitive tasks than neurotypical controls, and at least seven main functional domains appear to be implicated in ADHD. We discuss the underlying neural mechanisms of cognitive functions associated with ADHD, with emphasis on the neural basis of selective attention, demonstrating the feasibility of basic research approaches for further understanding cognitive behavioral processes as they relate to human psychopathology. The study of circuit-level mechanisms underlying executive functions in nonhuman primates holds promise for advancing our understanding, and ultimately the treatment, of ADHD.

Processing speed can monitor stimulant-medication effects in adults with attention deficit disorder with hyperactivity

BACKGROUND

Treatment responses to methylphenidate by adults with ADHD are generally monitored against DSM-IV/DSM-V symptomatology, rating scales or interviews during reviews.

AIMS

To evaluate the use of single- and dual-dimension processing-speed and efficiency measures to monitor the effects of pharmacological treatment with methylphenidate after a short period off medication.

METHODS

A Quick Test of Cognitive Speed (AQT) monitored the effects of immediate-release methylphenidate in 40 previously diagnosed and medicated adults with ADHD. Processing speed was evaluated with prior prescription medication, without medication after a 2-day period off ADHD medication, and with low-dose (10/20 mg) and high-dose (20/40 mg) methylphenidate hydrochloride (Medikinet IR).

RESULTS

Thirty-three participants responded to the experimental treatments. One-way ANOVA with post-hoc analysis (Scheffe) indicated significant main effects for single dimension colour and form and dual-dimension colour-form naming. Post-hoc analysis indicated statistical differences between the no- and high-dose medication conditions for colour and form, measures of perceptual speed. For colour-form naming, a measure of cognitive speed, there was a significant difference between no- and low-dose medication and between no- and high-dose medications, but not between low- and high-dose medications.

CONCLUSIONS

Results indicated that the AQT tests effectively monitored incremental effects of the methylphenidate dose on processing speed after a 2-day period off medication. Thus, perceptual (colour and form) and cognitive speed (two-dimensional colour-form naming) and processing efficiency (lowered shift costs) increased measurably with high-dose medication. These preliminary findings warrant validation with added measures of associated behavioural and cognitive changes.

Vitamin-Mineral Treatment of ADHD in Adults

OBJECTIVE

Despite widespread use, there is little data investigating the long-term impact of micronutrients on psychiatric disorders. This study investigated the naturalistic outcome 1-year post-baseline of a randomized controlled trials (RCT) that compared micronutrients with placebo in 80 adults with ADHD.

METHOD

All participants were contacted and clinician-rated questionnaires completed.

RESULTS

A total of 72 (90%) of the sample participated; although there was significant regression in psychiatric functioning from the end-of-trial on all measures, outcomes remained significantly improved from baseline. Dominant treatment from the end-of-treatment to follow-up was investigated as a mediator of outcome; those staying on the micronutrients performed better than those who switched to medications or discontinued micronutrients. Cost was the most substantial reason why people stopped micronutrient treatment.

CONCLUSION

For the small number of participants who stayed on micronutrients, the benefits conferred through the controlled trial were maintained. The results are limited by small sample, lack of blinding, expectation, and reliance on self-report of symptoms.

High reward expectancy during methylphenidate depresses the dopaminergic response to gain and loss

Dopamine plays an important role in goal-directed behavior, through its modulatory influence on striatal neurons. It is unclear whether tonic dopamine levels, which regulate the vigor of acting, interact with the phasic dopamine response to reward that drives instrumental behavior. In a randomized placebo-controlled study in healthy volunteers, we show that methylphenidate, a drug that increases tonic dopamine levels, systematically reduced striatal phasic BOLD responses to gain and loss in a gambling task as measured with fMRI. It also increased response vigor and reward expectancy-related BOLD signals in the ventral striatum. These findings suggest that striatal tonic dopamine levels constitute an average reward expectation signal that modulates the phasic dopaminergic response to reward. This offers opportunities for treatment of behavioral disorders associated with abnormal reward sensitivity.

Long-Term Memory Performance in Adult ADHD

OBJECTIVE

Memory problems are a frequently reported symptom in adult ADHD, and it is well-documented that adults with ADHD perform poorly on long-term memory tests. However, the cause of this effect is still controversial. The present meta-analysis examined underlying mechanisms that may lead to long-term memory impairments in adult ADHD.

METHOD

We performed separate meta-analyses of measures of memory acquisition and long-term memory using both verbal and visual memory tests. In addition, the influence of potential moderator variables was examined.

RESULTS

Adults with ADHD performed significantly worse than controls on verbal but not on visual long-term memory and memory acquisition subtests. The long-term memory deficit was strongly statistically related to the memory acquisition deficit. In contrast, no retrieval problems were observable.

CONCLUSION

Our results suggest that memory deficits in adult ADHD reflect a learning deficit induced at the stage of encoding. Implications for clinical and research settings are presented.

The relationship between nonmedical use of prescription stimulants, executive functioning and academic outcomes

The nonmedical use of prescription stimulants (NMUPS) is a prevalent issue among college students. The primary reason college students report NMUPS is for academic enhancement i.e., to perform better on schoolwork/tests and focus better in class. Executive functioning (EF), which includes abilities that allow for planning, cognitive flexibility, self-regulation, and goal-directed behavior, are potential mechanisms underlying academic performance. Preliminary research has revealed that college students with EF deficits are more likely to have educational difficulties and take part in risky behavior. Based on the literature, it is possible that students with EF deficits are engaging in NMUPS to help them overcome these deficits to succeed academically. Therefore, the purpose of the present study was to examine the relationship between NMUPS and EF among a sample of college students. The sample included 308 students from six public universities located in various regions of the United States. Measures used in this study were the SSQ, BDEFS and GPA. Results revealed 18.8% of the general sample reported NMUPS. Participants with clinically significant EF deficits reported significantly higher rates of NMUPS, compared to those without deficits in EF. NMUPS, however, did not moderate the relationship between EF and GPA. The present findings have implications for identifying sub-populations of college students who might be at risk for engaging in NMUPS and to improve prevention and intervention strategies aimed at reducing NMUPS. Limitations and suggestions for future research are discussed.

Comparison of baseline and post-concussion ImPACT test scores in young athletes with stimulant-treated and untreated ADHD

OBJECTIVES

Baseline and post-concussion neurocognitive testing is useful in managing concussed athletes. Attention deficit hyperactivity disorder (ADHD) and stimulant medications are recognized as potential modifiers of performance on neurocognitive testing by the Concussion in Sport Group. Our goal was to assess whether individuals with ADHD perform differently on post-concussion testing and if this difference is related to the use of stimulants.

METHODS

Retrospective case-control study in which 4373 athletes underwent baseline and post-concussion testing using the ImPACT battery. 277 athletes self-reported a history of ADHD, of which, 206 reported no stimulant treatment and 69 reported stimulant treatment. Each group was matched with participants reporting no history of ADHD or stimulant use on several biopsychosocial characteristics. Non-parametric tests were used to assess ImPACT composite score differences between groups.

RESULTS

Participants with ADHD had worse verbal memory, visual memory, visual motor speed, and reaction time scores than matched controls at baseline and post-concussion, all with p ≤ .001 and |r|≥ 0.100. Athletes without stimulant treatment had lower verbal memory, visual memory, visual motor speed, and reaction time scores than controls at baseline (p ≤ 0.01, |r|≥ 0.100 [except verbal memory, r = -0.088]) and post-concussion (p = 0.000, |r|> 0.100). Athletes with stimulant treatment had lower verbal memory (Baseline: p = 0.047, r = -0.108; Post-concussion: p = 0.023, r = -0.124) and visual memory scores (Baseline: p = 0.013, r = -0.134; Post-concussion: p = 0.003, r = -0.162) but equivalent visual motor speed and reaction time scores versus controls at baseline and post-concussion.

CONCLUSIONS

ADHD-specific baseline and post-concussion neuropsychological profiles, as well as stimulant medication status, may need to be considered when interpreting ImPACT test results. Further investigation into the effects of ADHD and stimulant use on recovery from sport-related concussion (SRC) is warranted.

Do college students improve their grades by using prescription stimulants nonmedically?

INTRODUCTION

Many college students engage in nonmedical use of prescription stimulants (NPS) because they believe it provides academic benefits, but studies are lacking to support or refute this belief.

METHODS

Using a longitudinal design, 898 undergraduates who did not have an ADHD diagnosis were studied. Year 3 GPA (from college records) of four groups was compared: Abstainers (did not engage in NPS either year; 68.8%); Initiators (NPS in Year 3 but not Year 2; 8.7%); Desisters (NPS in Year 2 but not Year 3; 5.8%); and Persisters (NPS in both years; 16.7%). Generalized estimating equations regression was used to estimate the association between NPS and change in GPA, controlling for sex and Year 2 GPA.

RESULTS

GPA increased significantly within Abstainers (p<0.05), but did not change significantly within the other groups. Overall, the relationship between NPS pattern group and change in GPA was not statistically significant (p=0.081). NPS was generally infrequent, but Persisters used more frequently than Desisters (11.7 versus 3.4days in Year 2) and Initiators (13.6 versus 4.0days in Year 3, both ps<0.001), controlling for sex and Year 2 GPA.

CONCLUSIONS

We cannot rule out the possibility that NPS prevented declines in GPA, but we can conclude that students who engaged in NPS showed no increases in their GPAs and gained no detectable advantages over their peers. The results suggest that prevention and intervention strategies should emphasize that the promise of academic benefits from NPS is likely illusory.

Methylphenidate, cognition, and epilepsy: A double-blind, placebo-controlled, single-dose study

OBJECTIVE

To evaluate the potential efficacy of immediate-release methylphenidate (MPH) for treating cognitive deficits in epilepsy.

METHODS

This was a double-blind, randomized, single-dose, 3-period crossover study in patients with epilepsy and chronic cognitive complaints comparing the effects of placebo and MPH 10 and 20 mg given 1 week apart. Cognitive outcome was evaluated on the basis of an omnibus z score calculated from performance on the Conners Continuous Performance Test 3 (ability to discriminate between target and nontarget stimuli [d'] and hit reaction time standard deviation), Symbol-Digit Modalities Test, and Medical College of Georgia Paragraph Memory Test. Adverse events and seizure frequency were monitored. An open-label follow-up is reported elsewhere.

RESULTS

Thirty-five adult patients with epilepsy participated, of whom 31 finished. Demographics included the following: mean age = 35.3 years (range 20-62 years), 13 men and 18 women, and baseline seizure frequency of 2.8 per month. Epilepsy types were focal (n = 24), generalized (n = 6), or unclassified (n = 1). Mean epilepsy duration was 12.5 years. A statistically significant performance benefit was present at both 10-mg (p = 0.030) and 20-mg (p = 0.034) MPH doses. No seizures were associated with either MPH dose. Adverse effects leading to withdrawal included cognitive "fogginess" (n = 1 on 20 mg), anxiety/agitation (n = 1 on 10 mg), and tachycardia (n = 1). One participant was lost to follow-up after one 20-mg dose without side effect.

CONCLUSIONS

This single-dose study suggests that MPH may be effective in ameliorating some cognitive deficits in patients with epilepsy. Additional studies are required.

CLINICALTRIALSGOV IDENTIFIER

NCT02178995.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that single doses of MPH improve cognitive performance on some measures of attention and processing speed in patients with epilepsy and cognitive complaints.