Differential long-term medication impact on executive function and delay aversion in ADHD

Relationship between two forms of impulsivity in mice at baseline and under acute and sub-chronic atomoxetine treatment

RATIONALE

Impulsivity is a symptom of various mental disorders, including attention deficit hyperactivity disorder (ADHD), bipolar disorder, and addiction. Impulsivity is not a unitary construct, but is present in different forms, yet only a few rodent studies have explored the relationship between these forms within individual subjects.

OBJECTIVES

In this study, we compared behaviors representing two impulsivity forms, delay discounting (choice impulsivity) and premature responding (waiting impulsivity), within the same mice.

METHODS

C57BL/6J male mice were concurrently trained and tested in the delay discounting task and the rodent continuous performance test in a counterbalanced design. The effects of the ADHD medication atomoxetine were tested in both tasks, after both acute (0.3-5.0 mg/kg) and sub-chronic (0.3 mg/kg twice daily for seven days) administration.

RESULTS

There was no correlation between the two impulsivity forms at baseline. Acute atomoxetine treatment (1, 3, and 5 mg/kg) significantly reduced premature responding. Furthermore, sub-chronic treatment with 0.3 mg/kg of atomoxetine caused a stable decrease in premature responding. Atomoxetine had no significant effect on delay discounting after acute or sub-chronic administration, although the acute administration of 1 mg/kg showed a trend towards increasing delay discounting.

CONCLUSIONS

The present results support that delay discounting and premature responding represent two different forms of impulsivity that show dissimilar responses to atomoxetine treatment. The consistency with findings in humans lends support to the translatability of the results in mice.

Fifty years of executive control research in attention-deficit/hyperactivity disorder:What we have learned and still need to know

For 50 years, attention-deficit/hyperactivity disorder (ADHD) has been considered a disorder of executive control (EC), the higher-order, cognitive skills that support self-regulation, goal attainment and what we generally call "attention." This review surveys our current understanding of the nature of EC as it pertains to ADHD and considers the evidence in support of eight hypotheses that can be derived from the EC theory of ADHD. This paper provides a resource for practitioners to aid in clinical decision-making. To support theory building, I draw a parallel between the EC theory of ADHD and the common gene-common variant model of complex traits such as ADHD. The conclusion offers strategies for advancing collaborative research.

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.

Effect of psychostimulant medications on functional balance performance in persons with Attention-Deficit/Hyperactivity Disorder: A systematic review

RATIONALE

Balance impairments are highly prevalent and underscreened in individuals with Attention-deficit/hyperactivity disorder (ADHD). Psychostimulant medications, used to treat ADHD symptoms, may improve balance performance in this population as demonstrated by a growing literature; however, there has not been a systematic investigation to understand the effects of psychostimulant medications on balance performance in individuals with ADHD. This systematic review examined the existing evidence to determine if psychostimulant medications improve balance performance in this population.

METHODS

We searched PubMed, CINAHL, SPORTDiscus, Scopus, Embase and Cochrane in March 2021 and in January 2022 to locate articles relevant to the topic. Two reviewers evaluated the methodological quality of included articles using the Study Quality Assessment Tools and the PEDro scale. The reviewers rated articles for the level of evidence based on the American Academy of Neurology (AAN) criteria. The reviewers further offered recommendations for research and clinical practice based on the strength of the reviewed articles using the AAN criteria. Additionally, the reviewers gleaned important characteristics from each article, such as study design, balance domain and study results.

RESULTS

Nine articles addressed the role of psychostimulant medications on balance outcomes. These articles included two Class II studies, two Class III studies and five Class IV studies. Based on study quality, this systematic review indicated low confidence in the use of psychostimulant medications for improving balance performance based on AAN criteria.

CONCLUSION

Psychostimulant medications trends to enhance balance performance in individuals with ADHD. However, the lack of well-designed studies and heterogeneity of balance measures warrant additional research.

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.

An evaluation of the effect of methylphenidate on working memory, time perception, and choice impulsivity in children with ADHD

Individuals with Attention-Deficit Hyperactivity Disorder (ADHD) consistently exhibit a stronger preference for immediate rewards than for larger rewards available following a delay on tasks measuring choice impulsivity (CI). Despite this, however, there remains a dearth of studies examining the impact of stimulant treatment on CI as well as associated higher order (e.g., working memory [WM]) and perceptual (e.g., time perception) cognitive processes. The present study examines the effect of osmotic release oral system methylphenidate (OROS-MPH) on CI, WM and time perception processes as well as the relation among these processes before and after taking a regimen of OROS-MPH. Thirty-five children (aged 7-12 years) with a diagnosis of ADHD participating in a concurrent stimulant medication study were recruited to complete computerized assessments of CI, WM, and time perception. Children completed the assessments after administration of a placebo as well as their lowest effective dose of OROS-MPH following a 2-week titration period. The results from one-sample t-tests indicated that OROS-MPH improves both CI and WM in youth with ADHD but does not impact time perception. Further, results revealed no significant association among the various indices of cognitive performance while taking placebo or OROS-MPH. Overall, the findings suggest that while OROS-MPH improves both CI and WM in youth with ADHD, improvements in CI as a result of OROS-MPH are unlikely to be associated with the improvements in WM given the lack of association among the two. Future studies should consider alternate cognitive, emotional, and motivational mechanisms that may account for the impact of OROS-MPH on CI. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Predictive scores failing at identifying psychiatric disabilities following childhood bacterial meningitis calls for revision of current follow-up guidelines

BACKGROUNDS

Psychiatric disabilities affect one in three survivors of bacterial meningitis. Since current guidelines do not recommend psychiatric follow-up in all children, disabilities are often detected late. Identifying children with elevated risk of psychiatric disabilities using predictive scores could be one strategy for detecting psychiatric disabilities without having to conduct psychiatric evaluations in all children. Therefore, we searched for existing predictive scores and later tested five predictive scores' ability to predict psychiatric disabilities following childhood bacterial meningitis.

METHODS

From an existing dataset, we selected 73 children with bacterial meningitis of whom 22 later developed psychiatric disease and 15 experienced concentration or learning difficulties. Using these, we tested each predictive score's sensitivity at their cut-off level for predicting psychiatric disease and concentration or learning difficulties using a chi-square test. Furthermore, we performed a receiver operating characteristic curve (ROC) analysis to assert the area under the curve (AUC) as a measure of overall predictive performance.

RESULTS

The sensitivity of each predictive score' ranged from 6 to 38% for psychiatric disease and from 8 to 57% for concentration or learning difficulties. In the ROC-analysis, the AUC was 0.59-0.73 and 0.53-0.72, respectively.

CONCLUSIONS

All predictive score failed at identifying children later developing psychiatric disabilities, excluding this as a feasible strategy for detecting psychiatric disabilities. Hence, current guidelines for bacterial meningitis need to be revised to recommend psychiatric evaluations in all children.KEY NOTESCurrent guidelines not recommending psychiatric evaluations in all children following bacterial meningitis may result in late detection of psychiatric disabilities.We tested predictive scores' ability to identify children later developing psychiatric disabilities following bacterial meningitis.All predictive score failed at identifying children later developing psychiatric disabilities, excluding this as a feasible strategy. Hence, current guidelines for bacterial meningitis need to be revised to recommend psychiatric evaluations in all children.

Adult Attention-Deficit Hyperactivity Disorder/Substance Use Disorder Dual Disorder Patients: A Dual Disorder Unit Point of View

Substance Use Disorders (SUDs) are often associated with Attention-Deficit Hyperactivity Disorder (ADHD) in adult populations due to multiple neurobiological, genetic, and psychosocial risk factors. This chapter provides a picture of the clinical aspects of adults with both ADHD and SUDs at treatment entry into a Dual Disorder Unit introducing the concept of different types of craving that may lead to substance use and abuse. At treatment entry, the presence of different comorbid SUD clusters, characterized by either stimulants/alcohol or by the use of cannabinoids, has not been shown to influence ADHD-specific symptomatology or severity, despite being crucial for the identification of a specific type of craving. We identified four clinical presentations of adult ADHD: Emotional Dysregulation, Substance Use, Core-ADHD Symptoms, and Positive Emotionality variants, that offer a practical guide in diagnosing and managing adult ADHD patients. Although the evidence of an effective medical treatment for Cocaine Use Disorder is insufficient, in our experience, toxicomanic behavior during stimulant treatment is sharply reduced in ADHD patients with cocaine addiction. Moreover, caffeinated compounds in military soldiers with ADHD may help reduce ADHD symptoms, making caffeine a potential pharmacological tool worth further investigation. Finally, substance use comorbidity does not influence treatment retention rate.

Effects of Atomoxetine Hydrochloride on Regulation of Lifespan in Drosophila Model

Nootropics (smart drugs) are used by students to enhance cognitive performance which have been reported times in recent years. However, some of the nootropics are central nervous system stimulants which are very likely to lead to addiction or complications such as vomiting and dizziness. Are there nootropics that can improve learning behavior while having potential positive effect on health? Here, we reported that Atomoxetine (ATX) has sex-specific effect on prolonging the life span of female Drosophila melanogaster. Further study indicated that ATX enhanced female resistance to heat stress and their vertical climbing ability, but it did decrease the number of eggs laid. ATX increased food-intake and sleep time both of females and males, and significantly reduced the 24h spontaneous activity of females and males. Our results present the sex dimorphic effect of ATX on life span regulation in Drosophila, and support further research on the beneficial role of ATX and the mechanisms in other animal models.

Psychiatric Disabilities and Other Long-term Consequences of Childhood Bacterial Meningitis

BACKGROUND

Bacterial meningitis is known to cause hearing impairments and neurologic deficits; however, less is known regarding psychiatric disabilities. In this study, we assessed psychiatric disabilities and other long-term consequences of childhood bacterial meningitis.

METHODS

From a previously validated dataset, we selected children having had bacterial meningitis. We then reviewed medical records and child health records from discharge onwards to identify disabilities. We calculated the occurrence of disabilities with a 95% confidence interval (CI), and we used a χ test to assess possible individual risk factors associated with occurrence of disabilities.

RESULTS

Of the 80 children included in this study, permanent disabilities not attributed to preexisting diseases were noted in 56% (CI: 45-67) during the mean observation period of 19 years and 2 months. Psychiatric disease was diagnosed in 30% (CI: 21-41), and another 5% (CI: 2-13) were under ongoing investigations for symptoms of psychiatric disease. Hearing impairments affected at least 30% (CI: 20-40), and neurologic deficits affected at least 23% (CI: 15-34). While other disabilities were often detected within the first year, psychiatric disabilities were detected after a mean time period of 14 years (CI: 11:1-16:11). Although some associations were noted, no individual risk factor was able to predict the occurrence of disabilities.

CONCLUSIONS

Psychiatric disabilities affect more than one-third of survivors and are among the most common long-term consequence of childhood bacterial meningitis. Late discovery and predictive difficulties call for a revision of current guidelines to include a specific long-term strategy for detecting psychiatric disabilities.

The Mechanism, Clinical Efficacy, Safety, and Dosage Regimen of Atomoxetine for ADHD Therapy in Children: A Narrative Review

Atomoxetine, a selective norepinephrine (NE) reuptake inhibitor, was approved for attention deficit/hyperactivity disorder (ADHD) treatment in children, adolescents and adults. We searched the database PubMed/MEDLINE (2000 to October 1, 2021). Only publications in English were considered. Atomoxetine inhibits the presynaptic norepinephrine transporter (NET), preventing the reuptake of NE throughout the brain along with inhibiting the reuptake of dopamine in specific brain regions such as the prefrontal cortex (PFC). The novel mechanism of atomoxetine also includes several new brain imaging studies and animal model studies. It is mainly metabolized by the highly polymorphic drug metabolizing enzyme cytochrome P450 2D6 (CYP2D6). Atomoxetine is effective and generally well tolerated. ADHD is often accompanied by multiple comorbidities. A series of studies have been published suggesting that atomoxetine is effective in the treatment of ADHD symptoms for children with various types of comorbidity. In some cases, it is possible that atomoxetine may have a positive influence on the symptoms of comorbidities. Atomoxetine can be administered either as a single daily dose or split into two evenly divided doses, and has a negligible risk of abuse or misuse. The latest guideline updated that clinical dose selection of atomoxetine was recommended based on both CYP2D6 genotype and the peak concentration. To have a more comprehensive understanding of atomoxetine, this review sets the focus on the mechanism, clinical efficacy and dosage regimen in detail, and also touches on those studies regarding adverse reactions of atomoxetine.

Is Methylphenidate Beneficial and Safe in Pharmacological Cognitive Enhancement?

Nootropics are drugs used to either treat or benefit cognition deficits. Among this class, methylphenidate is a popular agent, which acts through indirect dopaminergic and noradrenergic agonism and, therefore, is proposed to enhance performance in catecholamine-dependent cognitive domains such as attention, memory and prefrontal cortex-dependent executive functions. However, investigation into the efficacy of methylphenidate as a cognitive enhancer has yielded variable results across all domains, leading to debate within the scientific community surrounding its off-label use in healthy individuals seeking scholaristic benefit or increased productivity. Through analysis of experimental data and methodological evaluation, it is apparent that there are dose-, task- and domain-dependent considerations surrounding the use of methylphenidate in healthy individuals, whereby tailored dose administration is likely to provide benefit on an individual basis dependent on the domain of cognition in which benefit is required. Additionally, it is apparent that there are subjective effects of methylphenidate, which may increase user productivity irrespective of cognitive benefit. Whilst there is not extensive study in healthy older adults, it is plausible that there are dose-dependent benefits to methylphenidate in older adults in selective cognitive domains that might improve quality of life and reduce fall risk. Methylphenidate appears to produce dose-dependent benefits to individuals with attention-deficit/hyperactivity disorder, but the evidence for benefit in Parkinson's disease and schizophrenia is inconclusive. As with any off-label use of pharmacological agents, and especially regarding drugs with neuromodulatory effects, there are inherent safety concerns; epidemiological and experimental evidence suggests there are sympathomimetic, cardiovascular and addictive considerations, which might further restrict their use within certain demographics.

Executive function in XXY: Comparison of performance-based measures and rating scales

Few studies have systematically assessed executive functioning (EF) skills in boys with XXY, and these are limited by small samples and restricted EF assessment. This study used a broader battery of performance-based measures as well as parent-rating scales of EF in 77 boys and adolescents with XXY (mean age = 12.5 years), recruited from a clinical trial and an outpatient clinic. Exploratory factor analyses were used to create EF domains from performance-based measures, and similar domains were measured using the Behavior Rating Inventory of Executive Function and Conners Parent-Rating Scales. The boys with XXY showed a distinct EF profile, with the greatest deficit in attention and more moderate deficits in working memory, switching, and planning/problem solving. Parent ratings showed similar challenges, as well as impaired inhibition. Independent sample t-tests showed no difference on performance measures between boys diagnosed or not diagnosed with attention-deficit/hyperactivity disorder (ADHD), although parents of boys diagnosed with ADHD reported more difficulties. There were no differences on performance-based tests between those diagnosed pre- and postnatally, although parents of postnatally diagnosed boys reported more metacognitive problems. Language deficits, cognition, and socio-economic status did not account for EF deficits.

Using ADHD Medications to Treat Coexisting ADHD and Reading Disorders: A Systematic Review

Attention-deficit/hyperactivity disorder (ADHD), the most common pediatric neurobehavioral disorder, frequently presents with coexisting reading disorders (RDs). Despite this, it is unclear whether medication improves symptoms and function in children with comorbid ADHD and RD. We present a systematic review of studies investigating the effects of ADHD medications on ADHD symptoms, academic outcomes, and neuropsychological measures in this important group.

Delay Aversion and Executive Functioning in Adults With Attention-Deficit/Hyperactivity Disorder: Before and After Stimulant Treatment

BACKGROUND

Attention deficit hyperactivity disorder is a heterogeneous disorder, associated with deficits in motivation (e.g., delay aversion) and cognition. Methylphenidate is recommended as a first line treatment for attention deficit hyperactivity disorder symptoms, but little is known about its nonacute effects on motivational and cognitive deficits, particularly in adults with attention deficit hyperactivity disorder.

METHODS

We utilized a prospective, non-randomized, non-blinded, 6-week follow-up design with 42 initially stimulant medication-naïve adult patients with moderate to severe attention deficit hyperactivity disorder, and 42 age- and parental education-matched healthy controls. Delay aversion and executive functioning were assessed with 2 questionnaires and 5 performance-based tests.

RESULTS

At baseline, patients and controls differed significantly on performance-based measures (moderate to large effect sizes), and self-report of delay aversion and executive functioning (very large effect sizes). Treatment with methylphenidate medication (mean dose 65.54 mg/d, SD=10.39) was not associated with improvements in performance-based measures of delay aversion and executive functioning compared to controls, although improvements in self-report executive functioning and delay aversion were found. Self-reported delay aversion was most consistently associated with ADHD symptomatology at baseline and after medication.

CONCLUSION

Methylphenidate treatment does not have an effect on performance-based measures of delay aversion and executive functioning, but may have significant effects on self-reported delay aversion and executive functioning. The latter finding should be interpreted cautiously, given the subjective nature of these measures and design limitations. Self-reported delay aversion is most consistently associated with attention deficit hyperactivity disorder symptomatology.

How treatment improvement in ADHD and cocaine dependence are related to one another: A secondary analysis

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is overrepresented among individuals seeking treatment for substance use disorders. We previously reported that treatment with extended release mixed amphetamine salts (MAS-XR) increased abstinence, compared to placebo, among patients with co-occurring ADHD and cocaine dependence. This secondary analysis investigates the temporal relationship between ADHD improvement and cocaine abstinence in the first six weeks of the trial.

METHODS

The study was a three-arm, randomized, double-blinded, placebo-controlled, 14-week trial comparing MAS-XR (60 mg or 80 mg daily) versus placebo among 126 participants with ADHD and cocaine dependence. An autoregressive cross-lagged structural equation model was fit and evaluated weekly ADHD improvement (defined as ≥30% reduction in the Adult ADHD Investigator Symptom Rating Scale) and urine-confirmed abstinence over the first six weeks.

RESULTS

The proportion of patients with each of the possible overall patterns of response was: ADHD improves before cocaine abstinence: 24%; Cocaine abstinence occurs before ADHD improvement: 12%; ADHD improvement and abstinence occur during the same week: 6%; ADHD improves but abstinence never achieved: 34%; Abstinence achieved but ADHD never improves: 6%; Neither ADHD improvement nor abstinence: 18%. A significant cross-lagged association was found; subjects with ADHD improvement at week 2 had significantly higher odds of cocaine abstinence at week 3 (p = .014).

CONCLUSION

When treating co-occurring ADHD and cocaine dependence with stimulant medication, abstinence is most likely preceded by improvement in ADHD, which tends to occur early with medication treatment. Other observed temporal patterns suggest the potential complexity of the relationship between ADHD and cocaine dependence.