Increased risk of diseases of the basal ganglia and cerebellum in patients with a history of attention-deficit/hyperactivity disorder

Adult Attention Deficit-Hyperactivity Disorder is associated with Lewy Body Disease and Cognitive Impairment: A prospective cohort Study With 15-year Follow-Up

OBJECTIVES

Past reports have suggested that attention-deficit/hyperactivity disorder (ADHD) may be a risk factor for Lewy body disease (LBD). To confirm this relationship, we conducted the present study.

DESIGN

A prospective observational cohort study with a follow-up to 15 years.

SETTING

The subjects were recruited from cognitive neurology clinics, where they attended for a cognitive complaint or health check-up.

PARTICIPANTS

Two groups of subjects: ADHD adults and healthy subjects.

MEASUREMENTS

The risk of dementia and LBD was estimated with Kaplan-Meier analysis comparing for the presence or absence of ADHD with the log-rank test. Predictors of conversion were assessed through separate univariate and multivariate Cox regression analyses, adjusting for several variables.

RESULTS

The baseline sample consisted of 161 subjects with ADHD and 109 without ADHD. At the end of the follow-up, 31 subjects developed dementia, 27 cases in the ADHD group and 4 in comparison group. Dementia with Lewy bodies (DLB) was the most frequent type (N:20) of which 19 corresponded to the ADHD group. The incidence of non-amnestic-MCI in the ADHD group was higher representing 67.1 % of these subjects (N:108), and 17.4% (N:19) of healthy cases. The hazard ratios for dementia and LBD in the multivariate adjusted model were 3.33 (95% CI 1.0915 to 10.1699) and 54.54 (95% CI 7.4849 to 397.5028), respectively in the ADHD group.

CONCLUSIONS

This study showed that adult ADHD is independently associated with an increased risk of LBD, dementia, and na-MCI. Future studies should clarify this relationship to develop preventive measures for these patients.

Do prescription stimulants increase risk of Parkinson's disease among adults with attention-deficit hyperactivity disorder? A retrospective cohort study

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder in older adults that is associated with neuroinflammation, oxidative stress, and characterized by loss of dopaminergic cells. Illicit stimulants increase oxidative stress and are associated with increased risk of PD. Prescription stimulants are similar in mechanism to illicit stimulants, yet their influence on PD is not well described. This study aims to determine if prescription stimulants influence risk of PD among older adults with attention-deficit and hyperactivity disorder (ADHD).

METHODS

We implemented a retrospective observational cohort design utilizing the TriNetX database which sources from the electronic health records of 57 healthcare organizations. Inclusion criteria were ADHD diagnosis and age ≥50. Those exposed to stimulants and the unexposed controls were matched based on demographics and known risk factors for PD. The outcome of interest was the incidence of PD over a 30-year follow-up period. We utilized TriNetX software for hazard ratio (HR) analysis.

RESULTS

Among the 59,471 individuals treated with prescription stimulants 131 of them developed PD, and there were 272 individuals who developed PD that were not prescribed stimulants. This analysis yielded a HR of 0.419 (HR = 0.419 [95% CI 0.34, 0.516], P = 0.0013).

CONCLUSION

Illicit stimulants are associated with increased risk of PD, but this study suggests prescribed stimulants may not impart that same risk. The reduced risk in this cohort may be due to protection from illicit substance use and oxidative stress, however additional study exploring the relationship between prescription stimulants and PD is warranted.

Brain iron concentration in childhood ADHD: A systematic review of neuroimaging studies

Iron deficiency may play a role in the pathophysiology of Attention Deficit/Hyperactivity Disorder (ADHD). Due to its preponderant function in monoamine catecholamine and myelin synthesis, brain iron concentration may be of primary interest in the investigation of iron dysregulation in ADHD. This study reviewed current evidence of brain iron abnormalities in children and adolescents with ADHD using magnetic resonance imaging methods, such as relaxometry and quantitative susceptibility mapping, to assess brain iron estimates. The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A literature search was performed for studies published between January 1, 2008 and July 7, 2023 in Medline, Scopus and Proquest. Regions of interest, brain iron index values and phenotypical information were extracted from the relevant studies. Risk of bias was assessed using a modified version of the National Heart, Lung, and Blood Institute quality assessment tool. Seven cross-sectional studies comparing brain iron estimates in children with ADHD with neurotypical children were included. Significantly reduced brain iron content in medication-naïve children with ADHD was a consistent finding. Two studies found psychostimulant use may increase and normalize brain iron concentration in children with ADHD. The findings were consistent across the studies despite differing methodologies and may lay the early foundation for the recognition of a potential biomarker in ADHD, although longitudinal prospective neuroimaging studies using larger sample sizes are required. Lastly, the effects of iron supplementation on brain iron concentration in children with ADHD need to be elucidated.

Attention-Deficit/Hyperactivity Disorder as a Potential Risk Factor for Dementia and Other Neurocognitive Disorders: A Systematic Review

Background

Attention-deficit/hyperactivity disorder (ADHD), a common neurodevelopmental condition now recognized to persist into older adulthood, has been postulated to be a risk factor for neurocognitive disorders given the overlap in clinical features and neurobiology, as well as the complex interplay between ADHD and known risk factors for dementia. Studies have emerged assessing this relationship, but there has not yet been a comprehensive systematic review addressing this topic.

Objective

To assess whether ADHD is a risk factor for neurocognitive disorders and to explore possible mechanisms for such an association.

Methods

A systematic review of the literature was conducted using Medline, Embase, and PsycINFO from inception until June 4, 2023. Studies were included if they assessed whether or how ADHD may be a risk factor for neurocognitive disorders. Studies were excluded if they were not primary literature, not published in a peer-reviewed journal, not in English, and/or used non-human subjects. Study quality was assessed using the QualSyst tool.

Results

Sixteen studies met inclusion criteria. Seven studies found a positive association between ADHD and neurocognitive disorders (all-cause dementia in four studies, Alzheimer's disease in three studies, Lewy body dementia in two studies, and mild cognitive impairment in one study). Four studies did not find an association. Five studies pertained to possible mechanisms for an association, including genetics, with minimal significant findings.

Conclusions

ADHD may be a risk factor for certain neurocognitive disorders, although the evidence base is limited, and the absolute risk is small. Possible explanations include genetic and lifestyle factors.

IL-4 shapes microglia-dependent pruning of the cerebellum during postnatal development

Interleukin-4 (IL-4) is a type 2 cytokine with pleiotropic functions in adaptive immunity, allergies, and cognitive processes. Here, we show that low levels of IL-4 in the early postnatal stage delineate a critical period in which microglia extensively prune cerebellar neurons. Elevating the levels of this cytokine via peripheral injection, or using a mouse model of allergic asthma, leads to defective pruning, permanent increase in cerebellar granule cells, and circuit alterations. These animals also show a hyperkinetic and impulsive-like phenotype, reminiscent of attention-deficit hyperactivity disorder (ADHD). These alterations are blocked in Il4rαfl/fl::Cx3cr1-CreER mice, which are deficient in IL-4 receptor signaling in microglia. These findings demonstrate a previously unknown role for IL-4 during a neuroimmune critical period of cerebellar maturation and provide a first putative mechanism for the comorbidity between allergic disease and ADHD observed in humans.

[Epidemiology, diagnostics and treatment of attention deficit-hyperactivity disorder (ADHD) in advanced age]

Current studies demonstrate a comparably high prevalence of attention deficit-hyperactivity disorder (ADHD) in advanced age. Older people affected by ADHD suffer from a severe burden of psychiatric and somatic comorbidities as well as substantial impairment of social functioning and subjective well-being. The diagnostic differentiation from neurodegenerative diseases is particularly difficult in this age group. This narrative review summarizes the current knowledge about the epidemiology of ADHD in advanced age and possible relationships between ADHD and the risk for neurodegeneration. Furthermore, recommendations for diagnostics and treatment options of ADHD in advanced age are presented.

Risk of neurodegenerative disease or dementia in adults with attention-deficit/hyperactivity disorder: a systematic review

Purpose of review

Several psychiatric disorders have been associated with an increased risk of developing a neurodegenerative disease and/or dementia. Attention-deficit/hyperactivity disorder (ADHD), a neurodevelopmental disorder, has been understudied in relation to dementia risk. We summarized existing literature investigating the risk of incident neurodegenerative disease or dementia associated with ADHD.

Recent findings

We searched five databases for cohort, case-control, and clinical trial studies investigating associations between ADHD and neurodegenerative diseases/dementia in May 2023. Study characteristics were extracted by two independent raters, and risk of bias was assessed using the Newcastle Ottawa Scale. Search terms yielded 2,137 articles, and seven studies (five cohort and two case-control studies) ultimately met inclusion criteria. Studies examined the following types of neurodegeneration: all-cause dementia, Alzheimer's disease, Parkinson's and Lewy body diseases, vascular dementia, and mild cognitive impairment. Heterogeneity in study methodology, particularly covariates used in analyses and types of ratios for risk reported, prevented a meta-analysis and data were therefore summarized as a narrative synthesis. The majority of studies (4/7) demonstrated an overall low risk of bias.

Summary

The current literature on risk of developing a neurodegenerative disease in ADHD is limited. Although the studies identified present evidence for a link between ADHD and subsequent development of dementia, the magnitude of the direct effect of ADHD on neurodegeneration is yet to be determined and better empirically designed studies are first needed. Furthermore, the mechanism of how or why ADHD is associated with an increased risk of developing a neurocognitive disorder is still unclear and should be explored in future studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022348976, the PROSPERO number is CRD42022348976.

ADHD-A Clinician's Bird's Eye View of Current Status and New Vistas!

Objectives

Literature on ADHD has taken long strides recently as heaps of new data are pouring in through countless papers. Here, authors try to outline changing paradigms in ADHD practice. DSM-5 changes regarding the typology and diagnostic criteria are highlighted. Overview of co-morbidities, associations, developmental trajectories, and syndromic continuity across lifespan is outlined. Recent insights into aetiology and diagnostic tools are briefly discussed. New medications in the pipeline are also described.

Methods

EMBASE, Ovid MEDLINE, PubMed, Scopus, Web of Science, and Cochrane Database of Systemic Reviews were searched for all relevant updates in ADHD literature as of June, 2022.

Results

DSM-5 brought about changes to the diagnostic criteria of ADHD. These included replacing types with presentations, pushing age to 12, and, incorporating adult diagnostic criteria. In the same vein, DSM-5 allows now for diagnosing concurrent ADHD and ASD. Associations of ADHD to allergy, obesity, sleep disorders, and, epilepsy have been demonstrated in recent literature. Neurocircuity underlying ADHD has been extended beyond frontal-striatal to include CTC as well as DMN accounting for ADHD heterogeneity. NEBA was FDA-approved to differentiate ADHD from hyperkinetic ID. Atypical antipsychotics use to address behavioural facets in ADHD is on the rise with no solid evidence-base. α-2 agonists are FDA-approved as monotherapy or adjunctive to stimulants. Pharmacogenetic testing is readily available for ADHD. Different formulations of stimulants abound on the market widening clinicians' repertoire. Stimulant-related exacerbation of anxiety and tics were challenged in recent studies. Drugs for ADHD in the pipeline include-dasotraline, armodafinil, tipepidine, edivoxetine, metadoxine, and memantine.

Conclusions

Literature on ADHD keeps expanding towards advancing our understanding of the complex and heterogeneous intricacies of this commonplace neurodevelopmental disorder and hence informing better decisions on how best to manage its diverse cognitive, behavioural, social and medical facets.

Neurochemical, histological, and behavioral profiling of the acute, sub-acute, and chronic MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a heterogeneous multi-systemic disorder unique to humans characterized by motor and non-motor symptoms. Preclinical experimental models of PD present limitations and inconsistent neurochemical, histological, and behavioral readouts. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD is the most common in vivo screening platform for novel drug therapies; nonetheless, behavioral endpoints yielded amongst laboratories are often discordant and inconclusive. In this study, we characterized neurochemically, histologically, and behaviorally three different MPTP mouse models of PD to identify translational traits reminiscent of PD symptomatology. MPTP was intraperitoneally (i.p.) administered in three different regimens: (i) acute-four injections of 20 mg/kg of MPTP every 2 h; (ii) sub-acute-one daily injection of 30 mg/kg of MPTP for 5 consecutive days; and (iii) chronic-one daily injection of 4 mg/kg of MPTP for 28 consecutive days. A series of behavioral tests were conducted to assess motor and non-motor behavioral changes including anxiety, endurance, gait, motor deficits, cognitive impairment, circadian rhythm and food consumption. Impairments in balance and gait were confirmed in the chronic and acute models, respectively, with the latter showing significant correlation with lesion size. The sub-acute model, by contrast, presented with generalized hyperactivity. Both, motor and non-motor changes were identified in the acute and sub-acute regime where habituation to a novel environment was significantly reduced. Moreover, we report increased water and food intake across all three models. Overall, the acute model displayed the most severe lesion size, while across the three models striatal dopamine content (DA) did not correlate with the behavioral performance. The present study demonstrates that detection of behavioral changes following MPTP exposure is challenging and does not correlate with the dopaminergic lesion extent.

Centrality and interhemispheric coordination are related to different clinical/behavioral factors in attention deficit/hyperactivity disorder: a resting-state fMRI study

Eigenvector-Centrality (EC) has shown promising results in the field of Psychiatry, with early results also pertaining to ADHD. Parallel efforts have focused on the description of aberrant interhemispheric coordination in ADHD, as measured by Voxel-Mirrored-Homotopic-Connectivity (VMHC), with early evidence of altered Resting-State fMRI. A sample was collected from the ADHD200-NYU initiative: 86 neurotypicals and 89 participants with ADHD between 7 and 18 years old were included after quality control for motion. After preprocessing, voxel-wise EC and VMHC values between diagnostic groups were compared, and network-level values from 15 functional networks extracted. Age, ADHD severity (Connor's Parent Rating-Scale), IQ (Wechsler-Abbreviated-Scale), and right-hand dominance were correlated with EC/VMHC values in the whole sample and within groups, both at the voxel-wise and network-level. Motion was controlled by censoring time-points with Framewise-Displacement > 0.5 mm, as well as controlling for group differences in mean Framewise-Displacement values. EC was significantly higher in ADHD compared to neurotypicals in the left inferior Frontal lobe, Lingual gyri, Peri-Calcarine cortex, superior and middle Occipital lobes, right inferior Occipital lobe, right middle Temporal gyrus, Fusiform gyri, bilateral Cuneus, right Precuneus, and Cerebellum (FDR-corrected-p = 0.05). No differences were observed between groups in voxel-wise VMHC. EC was positively correlated with ADHD severity scores at the network level (at p-value < 0.01, Inattentive: Cerebellum rho = 0.273; Hyper/Impulsive: High-Visual Network rho = 0.242, Cerebellum rho = 0.273; Global Index Severity: High-Visual Network rho = 0.241, Cerebellum rho = 0.293). No differences were observed between groups for motion (p = 0.443). While EC was more related to ADHD psychopathology, VMHC was consistently and negatively correlated with age across all networks.

Stimulant Induced Movement Disorders in Attention Deficit Hyperactivity Disorder

Stimulants, such as amphetamine and methylphenidate, are one of the most effective treatment modalities for attention deficit hyperactivity disorder (ADHD) and may cause various movement disorders. This review discusses various movement disorders related to stimulant use in the treatment of ADHD. We reviewed the current knowledge on various movement disorders that may be related to the therapeutic use of stimulants in patients with ADHD. Recent findings suggest that the use of stimulants and the onset/aggravation of tics are more likely to be coincidental. In rare cases, stimulants may cause stereotypies, chorea, and dyskinesia, in addition to tics. Some epidemiological studies have suggested that stimulants used for the treatment of ADHD may cause Parkinson’s disease (PD) after adulthood. However, there is still a lack of evidence that the use of stimulants in patients with ADHD may cause PD, and related studies are only in the early stages. As stimulants are one of the most commonly used medications in children and adolescents, close observations and studies are necessary to assess the effects of stimulants on various movement disorders, including tic disorders and Parkinson’s disease.

ADHD and Neurodegenerative Disease Risk: A Critical Examination of the Evidence

In this review, we undertake a critical appraisal of eight published studies providing first evidence that a history of attention-deficit/hyperactivity disorder (ADHD) may increase risk for the later-life development of a neurodegenerative disease, in particular Lewy body diseases (LBD), by up to five-fold. Most of these studies have used data linked to health records in large population registers and include impressive sample sizes and adequate follow-up periods. We identify a number of methodological limitations as well, including potential diagnostic inaccuracies arising from the use of electronic health records, biases in the measurement of ADHD status and symptoms, and concerns surrounding the representativeness of ADHD and LBD cohorts. Consequently, previously reported risk associations may have been underestimated due to the high likelihood of potentially missed ADHD cases in groups used as “controls”, or alternatively previous estimates may be inflated due to the inclusion of confounding comorbidities or non-ADHD cases within “exposed” groups that may have better accounted for dementia risk. Prospective longitudinal studies involving well-characterized cases and controls are recommended to provide some reassurance about the validity of neurodegenerative risk estimates in ADHD.

Rise, and pronounced regional variation, in methylphenidate, amphetamine, and lisdexamfetamine distribution in the United States

Background

The prescription stimulants methylphenidate, amphetamine, and lisdexamfetamine are sympathomimetic drugs with therapeutic use. They are designated in the United States as Schedule II substances, defined by the 1970 Controlled Substances Act as having a “high potential for abuse”. Changing criteria for the diagnosis of Attention Deficit Hyperactivity Disorder in 2013 and the approval of lisdexamfetamine for binge eating disorder in 2015 may have impacted usage patterns. This report compared the pharmacoepidemiology of these stimulants in the United States from 2010–2017.

Methods

Distribution of amphetamine, methylphenidate, lisdexamfetamine were examined via weights extracted from the Drug Enforcement Administration’s (DEA) Automated Reports and Consolidated Ordering System (ARCOS). Median stimulant Daily Dosage per patient was determined for a regional analysis. The percent of cost and prescriptions attributable to each stimulant and atomoxetine in Medicaid from the “Drug Utilization 2018 - National Total” from the Centers for Medicare and Medicaid was determined.

Results

There was a rise in amphetamine (+67.5%) and lisdexamfetamine (+76.7%) from 2010–2017. The change in methylphenidate (−3.0%) was modest. Persons/day stimulant usage was lower in the West than in other US regions from 2014-2017. There was a negative correlation (r(48) = −0.43 to −0.65, p < .05) between the percent Hispanic population per state and the Daily Dosage/population per stimulant. Methylphenidate formulations accounted for over half (51.7%) of the $3.8 billion reimbursed by Medicaid and the plurality (45.4%) of the 22.0 million prescriptions. Amphetamine was responsible for less than one-fifth (18.4%) of cost but one-third of prescriptions (33.6%). Lisdexamfetamine’s cost (26.0%) exceeded prescriptions (16.3%).

Conclusion

The rising amphetamine and lisdexamfetamine distribution may correspond with a rise in adult ADHD diagnoses. Regional analysis indicates that stimulant distribution in the West may be distinct from that in other regions. The lower stimulant distribution in areas with greater Hispanic populations may warrant further study.

Caffeine-related genes influence anxiety disorders in children and adults with ADHD

Attention-deficit/hyperactivity disorder (ADHD) and anxiety disorders (AD) frequently co-occur, increasing morbidity and challenging treatment. Caffeine is a central nervous system stimulant and acts in the brain through adenosine receptors, influencing attention, alertness, and anxiety. In the present study, we performed a gene-set analysis to verify if genes related to caffeine response are associated with anxiety disorders in 240 children and 406 adults with ADHD. We demonstrated an association between the gene-set with AD in children (P = 0.0054) and with the number of anxiety disorders in adults (P = 0.0197). In order to test if this effect is a result of anxiety in general or is related to AD comorbid with ADHD, we evaluated the association between caffeine gene-set with AD in an adult control sample. The gene-set was neither associated with the AD presence (P = 0.3008) nor with the number of AD (P = 0.5594) in this control sample. We also test this gene set with ADHD (n = 55,374) and AD (n = 18,186) GWAS summary statistics, and we did not observe significant results with ADHD (P = 0.5587) or AD (P = 0.3930). These findings suggest the caffeine-related genes play a role in the etiology of an anxiety disorder phenotype present in children and adults with ADHD.

Longitudinal Cognitive Performance of Older Adults With ADHD Presenting to a Cognitive Neurology Clinic: A Case Series of Change Up to 21 Years

Background: The neuropsychological features of older adults with ADHD are largely unknown. This retrospective chart review aims to elucidate their cognitive trajectories using a case series of six older adults with ADHD presenting with memory complaints to a cognitive neurology clinic, whom we argue are a particularly relevant group to study due to their potential to mimic neurodegenerative syndromes.

Methods: Participants were included if they were age 40 or older at intake, had ADHD based on DSM-5 criteria, and had cognitive data collected prior to 2014 with follow-up at least 5 years later.

Results: Five men and one woman were included (M = 53.8 years at intake) and had an average of 135.0 months of follow-up data available. Despite notable between- and within-subject variability, cognition generally improved or remained stable across visits. Two participants experienced notable memory decline, but a global consideration of their performance in other domains suggests these deficits may be frontally-mediated.

Conclusion: In this small sample, cognition remained generally unchanged across 5–21 years. Isolated impairments likely reflect substantial intra-individual variability across time and measures.

Mapping phenotypic and aetiological associations between ADHD and physical conditions in adulthood in Sweden: a genetically informed register study

BACKGROUND

Emerging evidence suggests increased risk of several physical health conditions in people with ADHD. Only a few physical conditions have been thoroughly studied in relation to ADHD, and there is little knowledge on associations in older adults in particular. We aimed to investigate the phenotypic and aetiological associations between ADHD and a wide range of physical health conditions across adulthood.

METHODS

We did a register study in Sweden and identified full-sibling and maternal half-sibling pairs born between Jan 1, 1932, and Dec 31, 1995, through the Population and Multi-Generation Registers. We excluded individuals who died or emigrated before Jan 1, 2005, and included full-siblings who were not twins and did not have half-siblings. ICD diagnoses were obtained from the National Patient Register. We extracted ICD diagnoses for physical conditions, when participants were aged 18 years or older, from inpatient (recorded 1973-2013) and outpatient (recorded 2001-13) services. Diagnoses were regarded as lifetime presence or absence. Logistic regression models were used to estimate the associations between ADHD (exposure) and 35 physical conditions (outcomes) in individuals and across sibling pairs. Quantitative genetic modelling was used to estimate the extent to which genetic and environmental factors accounted for the associations with ADHD.

FINDINGS

4 789 799 individuals were identified (2 449 146 [51%] men and 2 340 653 [49%] women), who formed 4 288 451 unique sibling pairs (3 819 207 full-sibling pairs and 469 244 maternal half-sibling pairs) and 1 841 303 family clusters (siblings, parents, cousins, spouses). The mean age at end of follow-up was 47 years (range 18-81; mean birth year 1966); ethnicity data were not available. Adults with ADHD had increased risk for most physical conditions (34 [97%] of 35) compared with adults without ADHD; the strongest associations were with nervous system disorders (eg, sleep disorders, epilepsy, dementia; odds ratios [ORs] 1·50-4·62) and respiratory diseases (eg, asthma, chronic obstructive pulmonary disease; ORs 2·42-3·24). Sex-stratified analyses showed similar patterns of results in men and women. Stronger cross-disorder associations were found between full-siblings than between half-siblings for nervous system, respiratory, musculoskeletal, and metabolic diseases (p<0·007). Quantitative genetic modelling showed that these associations were largely explained by shared genetic factors (60-69% of correlations), except for associations with nervous system disorders, which were mainly explained by non-shared environmental factors.

INTERPRETATION

This mapping of aetiological sources of cross-disorder overlap can guide future research aiming to identify specific mechanisms contributing to risk of physical conditions in people with ADHD, which could ultimately inform preventive and lifestyle intervention efforts. Our findings highlight the importance of assessing the presence of physical conditions in patients with ADHD.

FUNDING

Swedish Research Council; Swedish Brain Foundation; Swedish Research Council for Health, Working Life, and Welfare; Stockholm County Council; StratNeuro; EU Horizon 2020 research and innovation programme; National Institute of Mental Health.

A Systematic Review and Comparison of Neurocognitive Features of Late-Life Attention-Deficit/Hyperactivity Disorder and Dementia With Lewy Bodies

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) in adulthood and dementia with Lewy bodies (DLB) share many cognitive and noncognitive similarities. The overlapping features between both disorders complicate differential diagnosis. The aim of the current systematic review was to compare patterns of neuropsychological profiles in older adults with ADHD and DLB.

METHOD

Of the 1989 ADHD-related articles and 1332 DLB-related articles screened, 3 ADHD and 25 DLB articles were retained for qualitative synthesis and review.

RESULTS

A synthesis of individual study findings revealed isolated working memory deficits for late-life ADHD, and performance deficits in areas of attention, memory, language, and visuoperceptual abilities for DLB. Results were limited by small samples and absence of data in some cognitive domains.

CONCLUSION

These initial findings support potentially unique neurocognitive profiles for ADHD in later life and DLB that would enable practitioners to differentially diagnose and appropriately treat older adults presenting with these phenotypically similar disorders.

The Association Between Parkinson's Disease and Attention-Deficit Hyperactivity Disorder

While Parkinson’s disease (PD) and attention-deficit hyperactivity disorder (ADHD) are two distinct conditions, it has been hypothesized that they share several overlapping anatomical and neurochemical changes. In order to investigate that hypothesis, this study used claims data from Taiwan’s Longitudinal Health Insurance Database 2000 to provide the significant nationwide population-based evidence of an increased risk of PD among ADHD patients, and the connection between the two conditions was not the result of other comorbidities. Moreover, this study showed that the patients with PD were 2.8 times more likely to have a prior ADHD diagnosis compared with those without a prior history of ADHD. Furthermore, an animal model of ADHD was generated by neonatally injecting rats with 6-hydroxydopamine (6-OHDA). These rats were subjected to behavior tests and the 99mTc-TRODAT-1 brain imaging at the juvenile stage. Compared to control group rats, the 6-OHDA rats showed a significantly reduced specific uptake ratio in the striatum, indicating an underlying PD-linked pathology in the brains of these ADHD phenotype-expressing rats. Overall, these results support that ADHD shares a number of anatomical and neurochemical changes with PD. As such, improved knowledge of the neurochemical mechanisms underlying ADHD could result in improved treatments for various debilitating neurological disorders, including PD.

New pharmacological and neuromodulation approaches for impulsive-compulsive behaviors in Parkinson's disease

INTRODUCTION

A significant proportion of patients with Parkinson's disease (PD) display a set of impulsive-compulsive behaviors at some point during the course of illness. These behaviors range from the so-called behavioral addictions to dopamine dysregulation syndrome, punding and hoarding disorders. These behaviors have been consistently linked to the use of dopaminergic medications used to treat PD motor symptoms (dopamine agonists, levodopa, and other agents) and less consistently to neuromodulation techniques such as deep brain stimulation (DBS). Since there are still no approved treatments for these conditions, their pharmacological management is still a big challenge for clinicians.

METHODS

We conducted an extensive review of current pharmacological and neuromodulation literature for the management of impulsive-compulsive disorders in PD patients.

RESULTS

Pharmacological treatment approaches for impulsive-compulsive behaviors and DDS in PD patients include reduction of levodopa (LD), reduction/cessation of dopamine agonist (DA), and initiation of infusion therapies (apomorphine infusion and duodopa). Also, atomoxetine, a noradrenergic agent approved for the treatment of attention deficit hyperactivity disorder, showed some interesting preliminary results but there is still a lack of controlled longitudinal studies. Finally, while DBS effects on impulsive-compulsive disorders are still controversial, non-invasive techniques (such as transcranial magnetic stimulation and transcranial direct current stimulation) could have a potential positive effect but, again, there is still a lack of controlled trials.

CONCLUSION

Managing impulsivity and compulsivity in PD patients is still a non-evidence-based challenge for clinicians. Controlled trials on promising approaches such as atomoxetine and non-invasive neuromodulation techniques are needed.

Is Attention-Deficit/Hyperactivity Disorder a Risk Syndrome for Parkinson's Disease?

Recent epidemiological evidence indicates that diagnosis of attention-deficit/hyperactivity disorder (ADHD) is associated with increased risk for diseases of the basal ganglia and cerebellum, including Parkinson's disease (PD). The evidence reviewed here indicates that deficits in striatal dopamine are a shared component of the causal chains that produce these disorders. Neuropsychological studies of adult ADHD, prodromal PD, and early-stage PD reveal similar deficits in executive functions, memory, attention, and inhibition that are mediated by similar neural substrates. These and other findings are consistent with the possibility that ADHD may be part of the PD prodrome. The mechanisms that may mediate the association between PD and ADHD include neurotoxic effects of stimulants, other environmental exposures, and Lewy pathology. Understanding the nature of the association between PD and ADHD may provide insight into the etiology and pathogenesis of both disorders. The possible contribution of stimulants to this association may have important clinical and public health implications.

Trends in stimulant dispensing by age, sex, state of residence, and prescriber specialty - United States, 2014-2019

BACKGROUND

Stimulant medications are commonly prescribed for the treatment of attention-deficit/hyperactivity disorder; however, they also have high potential for diversion and misuse. We estimated national stimulant dispensing trends from 2014 to 2019 and differences in dispensing by age, sex, state, prescriber specialty, payor type, patient copay, and stimulant type.

METHODS

We calculated rates of stimulant dispensing using IQVIA National Prescription Audit (NPA) New to Brand, NPA Regional, and NPA Extended Insights data, which provide dispensing estimates from approximately 49,900 pharmacies representing 92 % of prescriptions dispensed in the United States. Average annual percent change (AAPC) from 2014 to 2019 was analyzed using Joinpoint regression.

RESULTS

From 2014 to 2019, the national annual rate of stimulant dispensing increased significantly from 5.6 to 6.1 prescriptions per 100 persons. Rates differed by prescription stimulant type, with increases occurring among both amphetamine-type stimulants and long-acting stimulants. Rates among females (AAPC = 3.6 %; P = 0.001) and adults aged 20-39 years (AAPC=6.7 %; P = 0.002), 40-59 years (AAPC=9.7 %; P < 0.001), and ≥60 years (AAPC = 6.9 %; P = 0.001) increased significantly during the study period. Stimulant dispensing rates varied substantially across states, ranging from 1.0 per 100 in Hawaii to 13.6 per 100 in Alabama.

CONCLUSIONS

National stimulant dispensing rates increased from 2014 to 2019, driven by notable increases among females and adults aged ≥20 years. These trends should be considered when prescribing stimulants given growing concerns over prescription stimulant diversion, misuse, and related health harms.

Biomolecules and Electrochemical Tools in Chronic Non-Communicable Disease Surveillance: A Systematic Review

Over recent three decades, the electrochemical techniques have become widely used in biological identification and detection, because it presents optimum features for efficient and sensitive molecular detection of organic compounds, being able to trace quantities with a minimum of reagents and sample manipulation. Given these special features, electrochemical techniques are regularly exploited in disease diagnosis and monitoring. Specifically, amperometric electrochemical analysis has proven to be quite suitable for the detection of physiological biomarkers in monitoring health conditions, as well as toward the control of reactive oxygen species released in the course of oxidative burst during inflammatory events. Besides, electrochemical detection techniques involve a simple and swift assessment that provides a low detection-limit for most of the molecules enclosed biological fluids and related to non-transmittable morbidities.

Evaluation of causality between ADHD and Parkinson's disease: Mendelian randomization study

In a retrospective cohort study, patients with attention-deficit hyperactivity disorder (ADHD) and psychostimulant prescription were associated with increased risk of Parkinson's disease (PD). It is unclear whether ADHD per se or psychostimulant prescription is associated with PD. We aim to determine if genetic correlation or/and causal association exists between ADHD and PD using summary statistics obtained from the largest meta-analysis of genome-wide association studies of ADHD (20,183 cases; 35,191 controls) and PD (26,421 cases; 442,271 controls). Genetic correlation was tested between ADHD and PD by linkage disequilibrium score regression. Causal estimate was assessed by inverse-variance weighted (IVW) method as the main mendelian randomization analysis, with sensitivity analyses to detect horizontal pleiotropy. Weak and inverse genetic correlation existed between ADHD and PD (r=-0.100;SE=0.045;P = 0.026). Univariable IVW analysis with 10 and 77 genetic instruments respectively revealed null association for ADHD with PD (OR=0.930 per doubling in odds of ADHD; 95% CI:0.792-1.092) and PD with ADHD (OR=0.986 per doubling in odds of PD; 95% CI:0.956-1.015). Multivariable IVW analyses adjusted for BMI/smoking also revealed null association of ADHD with PD. Using 58 PD-associated genetic instruments, multivariable IVW analysis with/without adjustment for BMI/smoking suggested a weak and inverse causal association for PD on ADHD, but cautious interpretation is required. This well-powered study did not support causality between ADHD and PD. The observed positive association between ADHD and PD is more likely to be caused by unmeasured confounders. As psychostimulant use is associated with high risk of early-onset PD, future research should focus on this area.

Spontaneous and stimulus-driven rhythmic behaviors in ADHD adults and controls

Many aspects of human behavior are inherently rhythmic, requiring production of rhythmic motor actions as well as synchronizing to rhythms in the environment. It is well-established that individuals with ADHD exhibit deficits in temporal estimation and timing functions, which may impact their ability to accurately produce and interact with rhythmic stimuli. In the current study we seek to understand the specific aspects of rhythmic behavior that are implicated in ADHD. We specifically ask whether they are attributed to imprecision in the internal generation of rhythms or to reduced acuity in rhythm perception. We also test key predictions of the Preferred Period Hypothesis, which suggests that both perceptual and motor rhythmic behaviors are biased towards a specific personal 'default' tempo. To this end, we tested several aspects of rhythmic behavior and the correspondence between them, including spontaneous motor tempo (SMT), preferred auditory perceptual tempo (PPT) and synchronization-continuations tapping in a broad range of rhythms, from sub-second to supra-second intervals. Moreover, we evaluate the intra-subject consistency of rhythmic preferences, as a means for testing the reality and reliability of personal 'default-rhythms'. We used a modified operational definition for assessing SMT and PPT, instructing participants to tap or calibrate the rhythms most comfortable for them to count along with, to avoid subjective interpretations of the task. Our results shed new light on the specific aspect of rhythmic deficits implicated in ADHD adults. We find that individuals with ADHD are primarily challenged in producing and maintaining isochronous self-generated motor rhythms, during both spontaneous and memory-paced tapping. However, they nonetheless exhibit good flexibility for synchronizing to a broad range of external rhythms, suggesting that auditory-motor entrainment for simple rhythms is preserved in ADHD, and that the presence of an external pacer allows overcoming their inherent difficulty in self-generating isochronous motor rhythms. In addition, both groups showed optimal memory-paced tapping for rhythms near their 'counting-based' SMT and PPT, which were slightly faster in the ADHD group. This is in line with the predictions of the Preferred Period Hypothesis, indicating that at least for this well-defined rhythmic behavior (i.e., counting), individuals tend to prefer similar time-scales in both motor production and perceptual evaluation.

Orbitrap mass spectrometry for monitoring the ganglioside pattern in human cerebellum development and aging

We have developed here a superior approach based on high-resolution (HR) mass spectrometry (MS) for monitoring the changes occurring with development and aging in the composition and structure of cerebellar gangliosidome. The experiments were focused on the comparative screening and structural analysis of gangliosides expressed in fetal and aged cerebellum by Orbitrap MS with nanoelectrospray ionization (nanoESI) in the negative ion mode. The employed ultrahigh-resolution MS platform allowed the discrimination, without the need of previous separation, of 159 ions corresponding to 120 distinct species in the native ganglioside mixtures from fetal and aged cerebellar biopsies, many more than detected before, when MS platforms of lower resolution were employed. A number of gangliosides, in particular polysialylated belonging to GT, GQ, GP, and GS classes, modified by O-fucosylation, O-acetylation, or CH₃ COO^- were discovered here, for the first time in human cerebellum. These components, found differently expressed in fetal and aged tissues, indicated that the ganglioside profile in cerebellum is development stage- and age-specific. Following the fragmentation analysis by high-energy collision-induced dissociation (HCD) tandem MS (MS/MS), we have also observed that the intimate structure of certain compounds has not changed during the development and aging of the brain, an aspect which could open new directions in the investigation of ganglioside biomarkers in cerebellar tissue.

Alpha-synuclein/synapsin III pathological interplay boosts the motor response to methylphenidate

Loss of dopaminergic nigrostriatal neurons and fibrillary α-synuclein (α-syn) aggregation in Lewy bodies (LB) characterize Parkinson's disease (PD). We recently found that Synapsin III (Syn III), a phosphoprotein regulating dopamine (DA) release with α-syn, is another key component of LB fibrils in the brain of PD patients and acts as a crucial mediator of α-syn aggregation and toxicity. Methylphenidate (MPH), a monoamine reuptake inhibitor (MRI) efficiently counteracting freezing of gait in advanced PD patients, can bind α-syn and controls α-syn-mediated DA overflow and presynaptic compartmentalization. Interestingly, MPH results also efficient for the treatment of attention deficits and hyperactivity disorder (ADHD), a neurodevelopmental psychiatric syndrome associated with Syn III and α-syn polymorphisms and constituting a risk factor for the development of LB disorders. Here, we studied α-syn/Syn III co-deposition and longitudinal changes of α-syn, Syn III and DA transporter (DAT) striatal levels in nigrostriatal neurons of a PD model, the human C-terminally truncated (1-120) α-syn transgenic (SYN120 tg) mouse, in comparison with C57BL/6J wild type (wt) and C57BL/6JOlaHsd α-syn null littermates. Then, we analyzed the locomotor response of these animals to an acute administration of MPH (d-threo) and other MRIs: cocaine, that we previously found to stimulate Syn III-reliant DA release in the absence of α-syn, or the selective DAT blocker GBR-12935, along aging. Finally, we assessed whether these drugs modulate α-syn/Syn III interaction by fluorescence resonance energy transfer (FRET) and performed in silico studies engendering a heuristic model of the α-syn conformations stabilized upon MPH binding. We found that only MPH was able to over-stimulate a Syn III-dependent/DAT-independent locomotor activity in the aged SYN120 tg mice showing α-syn/Syn III co-aggregates. MPH enhanced full length (fl) α-syn/Syn III and even more (1-120) α-syn/Syn III interaction in cells exhibiting α-syn/Syn III inclusions. Moreover, in silico studies confirmed that MPH may reduce α-syn fibrillation by stabilizing a protein conformation with increased lipid binding predisposition. Our observations indicate that the motor-stimulating effect of MPH can be positively fostered in the presence of α-syn/Syn III co-aggregation. This evidence holds significant implications for PD and ADHD therapeutic management.

Chronic methylphenidate induces increased quinone production and subsequent depletion of the antioxidant glutathione in the striatum

BACKGROUND

Methylphenidate (Ritalin®) is a psychostimulant used chronically to treat attention deficit hyperactivity disorder. Methylphenidate acts by preventing the reuptake of dopamine and norepinephrine, resulting in an increase in these neurotransmitters in the synaptic cleft. Excess dopamine can be autoxidized to a quinone that may lead to oxidative stress. The antioxidant, glutathione helps to protect the cell against quinones via conjugation reactions; however, depletion of glutathione may result from excess quinone formation. Chronic exposure to methylphenidate appears to sensitize dopaminergic neurons to the Parkinsonian toxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We hypothesized that oxidative stress caused by the autooxidation of the excess dopamine renders dopaminergic neurons within the nigrostriatal pathway to be more sensitive to MPTP.

METHODS

To test this hypothesis, male mice received chronic low or high doses of MPH and were exposed to saline or MPTP following a 1-week washout. Quinone formation in the striatum was examined via dot blot, and striatal GSH was quantified using a glutathione assay.

RESULTS

Indeed, quinone formation increased with increasing doses of methylphenidate. Additionally, methylphenidate dose-dependently resulted in a depletion of glutathione, which was further depleted following MPTP treatment.

CONCLUSIONS

Thus, the increased sensitivity of dopamine neurons to MPTP toxicity following chronic methylphenidate exposure may be due to quinone production and subsequent depletion of glutathione.

Speech Processing Difficulties in Attention Deficit Hyperactivity Disorder

The large body of research that forms the ease of language understanding (ELU) model emphasizes the important contribution of cognitive processes when listening to speech in adverse conditions; however, speech-in-noise (SIN) processing is yet to be thoroughly tested in populations with cognitive deficits. The purpose of the current study was to contribute to the field in this regard by assessing SIN performance in a sample of adolescents with attention deficit hyperactivity disorder (ADHD) and comparing results with age-matched controls. This population was chosen because core symptoms of ADHD include developmental deficits in cognitive control and working memory capacity and because these top-down processes are thought to reach maturity during adolescence in individuals with typical development. The study utilized natural language sentence materials under experimental conditions that manipulated the dependency on cognitive mechanisms in varying degrees. In addition, participants were tested on cognitive capacity measures of complex working memory-span, selective attention, and lexical access. Primary findings were in support of the ELU-model. Age was shown to significantly covary with SIN performance, and after controlling for age, ADHD participants demonstrated greater difficulty than controls with the experimental manipulations. In addition, overall SIN performance was strongly predicted by individual differences in cognitive capacity. Taken together, the results highlight the general disadvantage persons with deficient cognitive capacity have when attending to speech in typically noisy listening environments. Furthermore, the consistently poorer performance observed in the ADHD group suggests that auditory processing tasks designed to tax attention and working memory capacity may prove to be beneficial clinical instruments when diagnosing ADHD.

Emerging challenges in pharmacotherapy research on attention-deficit hyperactivity disorder-outcome measures beyond symptom control and clinical trials

Although pharmacological therapies are recommended as a key component in the treatment of attention-deficit hyperactivity disorder, their use continues to prompt intense debate. Despite considerable research efforts, several gaps in the knowledge base and several questions over the quality of evidence exist. Particular issues surrounding pharmacological treatments include uncertainties about long-term effectiveness and safety, safety profiles in adults, and the comparative effectiveness of different medications. In this Review, we focus on four key methodological issues for future research: (1) the use of appropriate trial designs; the need for (2) outcome measures targeting effectiveness beyond symptom control and (3) safety outcome measures; and (4) the application of clinical and administrative research databases to assess real-world outcomes. Potential solutions include increased use of randomised placebo-controlled withdrawal trials and large pharmacoepidemiological studies that use electronic health-care records on the long-term effectiveness and safety of medications. Pragmatic head-to-head randomised trials would also provide direct evidence on comparative effectiveness and safety profiles.

Dopamine compartmentalization, selective dopaminergic vulnerabilities in Parkinson's disease and therapeutic opportunities

Progressive depletion of selected dopamine neurons is central to much Parkinson's disease (PD) disability. Although symptomatic treatments can ameliorate the disabilities that this neuronal depletion causes, no current strategy is documented to slow these losses. There is substantial evidence that dopamine in intracytoplasmic/extravesicular neuronal compartments can be toxic. Here, I review evidence that supports roles for dopamine compartmentalization, mediated largely by serial actions of plasma membrane SLC6A3/DAT and vesicular SLC18A2/VMAT2 transporters, in the selective patterns of dopamine neuronal loss found in PD brains. This compartmentalization hypothesis for the dopamine cell type specificity of PD lesions nominates available drugs for amelioration of damage arising from miscompartmentalized dopamine and raises cautions in using other drugs.