Stimulant medications for the treatment of ADHD: Efficacy and limitations

ADHD Diagnosis and Treatment Guidelines: A Historical Perspective

Attention-deficit/hyperactivity disorder (ADHD) is the most common behavioral condition and the second most common chronic illness in children. The observance of specific behaviors in multiple settings have remained the most successful method for diagnosing the condition, and although there are differences in specific areas of the brain, and a high heritability estimate (∼76%), they are not diagnostically specific. Medications, and particularly stimulant medication, have undergone rigorous studies to document their efficacy dating back to the 1970s. Likewise, behavioral interventions in the form of parent training and classroom programs have demonstrated robust efficacy during the same time period. Both medication and behavioral interventions are symptomatic treatments. The availability of only symptomatic treatments places ADHD in the same category as other chronic conditions such as diabetes and asthma. Successful treatment of most individuals requires ongoing adherence to the therapy. Improved communication between patients and their families, primary and mental health providers, and school personnel is necessary for effective ADHD treatment. Further enhancement of electronic systems to facilitate family, school, and provider communication can improve monitoring of ADHD symptoms and functional performance. The American Academy of Pediatrics ADHD guidelines were initially developed to help primary care clinicians address the needs of their patients with ADHD and were further refined with the second revision in 2019.

Basic processes as foundations of cognitive impairment in adult ADHD

Attention deficit hyperactivity disorder (ADHD) in adulthood is associated with impairment of multiple aspects of cognition which adversely affect the individual's everyday functioning. However, little is known about how these impairments are intertwined. This study explores whether impairments in basic processes (processing speed and distractibility) in adults with ADHD explain impairments in higher order functions, namely executive functions, memory, and complex attention. Furthermore, it is explored whether pharmacological treatment with methylphenidate (MPH) affects basic processes and higher order functions. A between-subjects design compared patients with ADHD without stimulant drug treatment (N = 55) and patients with ADHD treated with MPH (N = 31) with a healthy control group (N = 80). A neuropsychological test battery assessing basic processes and higher order functions was administered. Hierarchical logistic regression analyses were performed to evaluate the contribution of basic processes to impairments in higher order functions. Patients with ADHD not treated with MPH showed impairments in basic processes and higher order functions compared to controls. The impairments in basic processes explained 41-43% of impairments in executive functions, 27-29% in memory, and 56-74% in complex attention. In patients with ADHD treated with MPH, basic processes were not impaired and did not contribute significantly to impairments of higher order functions. Basic processes may constitute part of the foundation of cognitive impairments in adult ADHD. MPH may improve cognitive performance, presumably through improving basic processes. Applying this information could optimize neuropsychological assessments and inform treatment strategies by targeting basic processes.

Using task performance to inform treatment planning for youth with ADHD: A systematic review

The role that neuropsychological task performance plays in the assessment of Attention-Deficit/Hyperactivity Disorder (ADHD) is currently ambiguous, and findings are mixed regarding whether tasks have validity for diagnosing the disorder. Irrespective of their validity for diagnosing ADHD, neuropsychological tasks could provide valuable information to mental health professionals if they can inform recommendations for treatment targets and modalities. Therefore, this review sought to synthesize the available evidence related to the use of neuropsychological task performance as a tool for informing treatment planning for youth with ADHD. Reviewed studies focused on examinations of associations between task performance and academic, social, and health outcomes, as well as response to treatment. Twenty-five relevant studies using samples of youth diagnosed with ADHD in clinical, community, and school settings were identified. Review of the evidence suggests that task performance may be useful in identifying individuals with ADHD at risk for academic impairment. However, the evidence is less compelling for identifying youth at risk for impaired social functioning or poor health outcomes. The review also found that task performance is likely useful for predicting response to treatment with methylphenidate. Across studies, evidence indicated that interpreting task performance in an integrated manner, such as a factor score or mean score, was more consistently useful for predicting outcomes of interest than interpreting performance from a single task. Implications for the use of tasks in ADHD assessments are discussed, and future directions are outlined for further examining the clinical utility of task performance.

Melatonin in Youth: N-of-1 trials in a stimulant-treated ADHD Population (MYNAP): study protocol for a randomized controlled trial

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a common neurological disorder affecting 5 % of children worldwide. A prevalent problem for children with ADHD is initial insomnia. The gold standard treatment to manage ADHD symptoms is stimulant medications, which may exacerbate the severity of existing initial insomnia. Currently, no gold standard treatment option exists for initial insomnia for these children. Melatonin, a hormone and a popular natural health product, is commonly provided to children by parents and recommended by healthcare providers, but high quality pediatric evidence is lacking.

METHODS/DESIGN

This trial is a multicenter randomized triple-blind, placebo-controlled, parallel-group, randomized, controlled trial (RCT), in which each participant is offered an N-of-1 trial. An N-of-1 trial is a multiple-crossover, randomized, controlled trial conducted in a single individual. For the N-of-1 trial, each participant will undergo three pairs of treatment/placebo periods; each period is 1 week in length. Half the participants will have melatonin in the first period, the other half will start with placebo, and this will make up the parallel-group RCT. The primary outcome will be mean difference in sleep onset latency as measured by sleep diaries. A comparison of treatment effects yielded by the RCT data versus the aggregated N-of-1 trial data will also be assessed.

DISCUSSION

This trial will provide rigorous evidence for the effectiveness of melatonin in children with ADHD on stimulants who experience initial insomnia. Further, this study will provide the first prospectively planned head-to-head comparison of RCT data with pooled data from a series of N-of-1 trials. Aggregated N-of-1 trials may be a powerful tool to produce high quality clinical trial evidence.

TRIAL REGISTRATION NUMBERS

ClinicalTrials.gov, NCT02333149 . Registered on 16 December 2014. Australian New Zealand Clinical Trials Registry, ACTRN12614000542695 . Registered on 21 May 2014.

Amphetamines for attention deficit hyperactivity disorder (ADHD) in children and adolescents

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is one of the most common psychiatric conditions affecting children and adolescents. Amphetamines are among the most commonly prescribed medications to manage ADHD. There are three main classes of amphetamines: dexamphetamine, lisdexamphetamine and mixed amphetamine salts, which can be further broken down into short- and long-acting formulations. A systematic review assessing their efficacy and safety in this population has never been conducted.

OBJECTIVES

To assess the efficacy and safety of amphetamines for ADHD in children and adolescents.

SEARCH METHODS

In August 2015 we searched CENTRAL, Ovid MEDLINE, Embase, PsycINFO, ProQuest Dissertation and Theses, and the Networked Digital Library of Theses and Dissertations. We also searched ClinicalTrials.gov, and checked the reference lists of relevant studies and reviews identified by the searches. No language or date restrictions were applied.

SELECTION CRITERIA

Parallel-group and cross-over randomized controlled trials (RCTs) comparing amphetamine derivatives against placebo in a pediatric population (< 18 years) with ADHD.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data on participants, settings, interventions, methodology, and outcomes for each included study. For continuous outcomes, we calculated the standardized mean difference (SMD) and for dichotomous outcomes we calculated the risk ratio (RR). Where possible, we conducted meta-analyses using a random-effects model. We also performed a meta-analysis of the most commonly reported adverse events in the primary studies.

MAIN RESULTS

We included 23 trials (8 parallel-group and 15 cross-over trials), with 2675 children aged three years to 17 years. All studies compared amphetamines to placebo. Study durations ranged from 14 days to 365 days, with the majority lasting less than six months. Most studies were conducted in the United States; three studies were conducted across Europe. We judged 11 included studies to be at a high risk of bias due to insufficient blinding methods, failing to account for dropouts and exclusions from the analysis, and failing to report on all outcomes defined a priori. We judged the remaining 12 studies to be at unclear risk of bias due to inadequate reporting.Amphetamines improved total ADHD core symptom severity according to parent ratings (SMD -0.57; 95% confidence interval (CI) -0.86 to -0.27; 7 studies; 1247 children/adolescents; very low quality evidence), teacher ratings (SMD -0.55; 95% CI -0.83 to -0.27; 5 studies; 745 children/adolescents; low quality evidence), and clinician ratings (SMD -0.84; 95% CI -1.32 to -0.36; 3 studies; 813 children/adolescents; very low quality evidence). In addition, the proportion of responders as rated by the Clinical Global Impression - Improvement (CGI-I) scale was higher when children were taking amphetamines (RR 3.36; 95% CI 2.48 to 4.55; 9 studies; 2207 children/adolescents; very low quality evidence).The most commonly reported adverse events included decreased appetite, insomnia/trouble sleeping, abdominal pain, nausea/vomiting, headaches, and anxiety. Amphetamines were associated with a higher proportion of participants experiencing decreased appetite (RR 6.31; 95% CI 2.58 to 15.46; 11 studies; 2467 children/adolescents), insomnia (RR 3.80; 95% CI 2.12 to 6.83; 10 studies; 2429 children/adolescents), and abdominal pain (RR 1.44; 95% CI 1.03 to 2.00; 10 studies; 2155 children/adolescents). In addition, the proportion of children who experienced at least one adverse event was higher in the amphetamine group (RR 1.30; 95% CI 1.18 to 1.44; 6 studies; 1742 children/adolescents; low quality evidence).We performed subgroup analyses for amphetamine preparation (dexamphetamine, lisdexamphetamine, mixed amphetamine salts), amphetamine release formulation (long acting versus short acting), and funding source (industry versus non industry). Between-group differences were observed for proportion of participants experiencing decreased appetite in both the amphetamine preparation (P < 0.00001) and amphetamine release formulation (P value = 0.008) subgroups, as well as for retention in the amphetamine release formulation subgroup (P value = 0.03).

AUTHORS' CONCLUSIONS

Most of the included studies were at high risk of bias and the overall quality of the evidence ranged from low to very low on most outcomes. Although amphetamines seem efficacious at reducing the core symptoms of ADHD in the short term, they were associated with a number of adverse events. This review found no evidence that supports any one amphetamine derivative over another, and does not reveal any differences between long-acting and short-acting amphetamine preparations. Future trials should be longer in duration (i.e. more than 12 months), include more psychosocial outcomes (e.g. quality of life and parent stress), and be transparently reported.

Attention Deficit Hyperactivity Disorder and oxidative stress: A short term follow up study

In this study, we aimed to investigate total antioxidative status (TAS) and total oxidative status (TOS) of plasma and antioxidant enzymes such as paraoxonase (PON), stimulated paraoxonase (SPON), arylesterase (ARES) and thiols in plasma of children and adolescents with Attention Deficit Hyperactivity Disorder (ADHD). In the second step. this study aimed to reveal the possible effects of ADHD treatment on these parameters. Fifty-six patients with ADHD and 52 healthy controls were involved in this study. Venous blood samples were collected and oxidative and antioxidative parameter's were studied. In the second phase of the study, blood samples were taken from patients using medication. Pre-treatment oxidative stress index (OSI) values and the plasma TOS levels of the patients with ADHD were statistically higher than those of the control group. The plasma thiol levels of the patients with ADHD were significantly lower than the control group. The post-treatment plasma antioxidative parameter's levels were significantly higher than the pre-treatment levels. The post-treatment oxidative stress index value was significantly lower than the pre-treatment value. Therefore, oxidative metabolism was found to be impaired in children and adolescents with ADHD. It was also determined that methylphenidate repairs the oxidative balance by increasing antioxidant defence mechanisms.

Do stimulant medications improve educational and behavioral outcomes for children with ADHD?

We examine the effects of a policy change in the province of Quebec, Canada which greatly expanded insurance coverage for prescription medications. We show that the change was associated with a sharp increase in the use of stimulant medications commonly prescribed for ADHD in Quebec relative to the rest of Canada. We ask whether this increase in medication use was associated with improvements in emotional functioning or academic outcomes among children with ADHD. We find little evidence of improvement in either the medium or the long run. Our results are silent on the effects on optimal use of medication for ADHD, but suggest that expanding medication in a community setting had little positive benefit and may have had harmful effects given the average way these drugs are used in the community.

Good vibrations--effects of whole body vibration on attention in healthy individuals and individuals with ADHD

OBJECTIVES

Most of the current treatment strategies of ADHD are associated with a number of disadvantages which strengthen the need for alternative or additional approaches for the treatment of ADHD. In this respect, Whole Body Vibration (WBV) might be interesting as it was found to have beneficial effects on a variety of physiological measures. The present study explored the effects of WBV on attention of healthy individuals and adults diagnosed with ADHD.

METHODS

Eighty-three healthy individuals and seventeen adults diagnosed with ADHD participated in the study. WBV treatment was applied passively, while participants were sitting on a chair which was mounted on a vibrating platform. A repeated measure design was employed in order to explore potential effects of WBV treatment on attention within subjects. Attention (i.e. inhibitory control) was measured with a color-word interference paradigm.

RESULTS

A period of two minutes of WBV treatment had significant beneficial effects of small to medium size on attention of both healthy individuals and adults with ADHD. The effect of WBV treatment on attention did not differ significantly between groups.

CONCLUSIONS

WBV was demonstrated to improve cognitive performance of healthy individuals as well as of individuals with ADHD. WBV treatment is relatively inexpensive and easy to apply and might therefore be of potential relevance for clinical use. The application of WBV treatment as a cognitive enhancement strategy and as a potential treatment of cognitive impairments is discussed.

Neurofeedback and cognitive attention training for children with attention-deficit hyperactivity disorder in schools

OBJECTIVE

To evaluate the efficacy of 2 computer attention training systems administered in school for children with attention-deficit hyperactivity disorder (ADHD).

METHOD

Children in second and fourth grade with a diagnosis of ADHD (n = 104) were randomly assigned to neurofeedback (NF) (n = 34), cognitive training (CT) (n = 34), or control (n = 36) conditions. A 2-point growth model assessed change from pre-post intervention on parent reports (Conners 3-Parent [Conners 3-P]; Behavior Rating Inventory of Executive Function [BRIEF] rating scale), teacher reports (Swanson, Kotkin, Agler, M-Flynn and Pelham scale [SKAMP]; Conners 3-Teacher [Conners 3-T]), and systematic classroom observations (Behavioral Observation of Students in Schools [BOSS]). Paired t tests and an analysis of covariance assessed change in medication.

RESULTS

Children who received NF showed significant improvement compared with those in the control condition on the Conners 3-P Attention, Executive Functioning and Global Index, on all BRIEF summary indices, and on BOSS motor/verbal off-task behavior. Children who received CT showed no improvement compared to the control condition. Children in the NF condition showed significant improvements compared to those in the CT condition on Conners 3-P Executive Functioning, all BRIEF summary indices, SKAMP Attention, and Conners 3-T Inattention subscales. Stimulant medication dosage in methylphenidate equivalencies significantly increased for children in the CT (8.54 mg) and control (7.05 mg) conditions but not for those in the NF condition (0.29 mg).

CONCLUSION

Neurofeedback made greater improvements in ADHD symptoms compared to both the control and CT conditions. Thus, NF is a promising attention training treatment intervention for children with ADHD.

Methylphenidate induces lipid and protein damage in prefrontal cortex, but not in cerebellum, striatum and hippocampus of juvenile rats

The use of psychostimulant methylphenidate has increased in recent years for the treatment of attention-deficit hyperactivity disorder in children and adolescents. However, the behavioral and neurochemical changes promoted by its use are not yet fully understood, particularly when used for a prolonged period during stages of brain development. Thus, the aim of this study was to determine some parameters of oxidative stress in encephalic structures of juvenile rats subjected to chronic methylphenidate treatment. Wistar rats received intraperitoneal injections of methylphenidate (2.0 mg/kg) once a day, from the 15th to the 45th day of age or an equivalent volume of 0.9% saline solution (controls). Two hours after the last injection, animals were euthanized and the encephalic structures obtained for determination of oxidative stress parameters. Results showed that methylphenidate administration increased the activities of superoxide dismutase and catalase, but did not alter the levels of reactive species, thiobarbituric acid reactive substances levels and sulfhydryl group in cerebellum of rats. In striatum and hippocampus, the methylphenidate-treated rats presented a decrease in the levels of reactive species and thiobarbituric acid reactive substances, but did not present changes in the sulfhydryl groups levels. In prefrontal cortex, methylphenidate promoted an increase in reactive species formation, SOD/CAT ratio, and increased the lipid peroxidation and protein damage. These findings suggest that the encephalic structures respond differently to methylphenidate treatment, at least, when administered chronically to young rats. Notably, the prefrontal cortex of juvenile rats showed greater sensitivity to oxidative effects promoted by methylphenidate in relation to other encephalic structures analyzed.

Motor skills of children newly diagnosed with Attention Deficit Hyperactivity Disorder prior to and following treatment with stimulant medication

Motor difficulties are common in children with Attention Deficit Hyperactivity Disorder (ADHD). Although preliminary evidence has suggested that methylphenidate can improve the motor skills in children with ADHD and Developmental Coordination Disorder (DCD), the effect of stimulant medication on motor performance in children newly diagnosed with ADHD with or without motor impairment remains unclear. A cohort study of 49 medication-naïve children (39 male; mean age 8.4±1.3 years) with ADHD was conducted. Children were evaluated using the Movement Assessment Battery for Children and the developmental test of visual motor integration at diagnosis and again three months following daily treatment with a stimulant medication. Motor difficulties were highly present at baseline (73.5%) but resolved in a subset after treatment with stimulant medication, suggesting that their motor difficulties may be attributed in part to their attentional problems. Nevertheless, motor impairment persisted in 55.1% of the sample. The severity of the behavioural symptoms was significantly associated with balance skills in children without motor impairments (r(2)=0.30, p<0.01) and with visual motor integration skills in children with persisting motor difficulties (r(2)=0.27, p<0.01). Attentional difficulties negatively affect the motor skills of children with ADHD. Following the use of stimulant medication, an important subset continued to demonstrate motor difficulties. The improvement in behaviour was insufficient to resolve motor problems and these children should therefore be targeted for rehabilitation services.

Chronic methylphenidate administration alters antioxidant defenses and butyrylcholinesterase activity in blood of juvenile rats

Methylphenidate (MPH), a psychostimulant that affects both dopaminergic and noradrenergic systems, is one of the most frequently prescribed treatments for attention-deficit hyperactivity disorder. The present study investigated the effects of chronic administration of MPH on some parameters of oxidative stress, as well as on butyrylcholinesterase (BuChE) activity in blood of young rats. Rats received intraperitoneal injections of MPH (2.0 mg/kg) once a day, from the 15th to the 45th day of age or an equivalent volume of 0.9% saline solution (controls). Two hours after the last injection, animals were euthanized, and blood was collected. Results demonstrated that MPH did not alter the dichlorofluorescein formed, decreased both thiobarbituric acid reactive substances and total non-enzymatic radical-trapping antioxidant, and increased superoxide dismutase and catalase activities, suggesting that this psychostimulant may alter antioxidant defenses. BuChE activity was increased in blood of juvenile rats subjected to chronic MPH administration. These findings suggest that MPH may promote peripheral oxidative adaptations and cholinergic changes.

Relation between therapeutic response and side effects induced by methylphenidate as observed by parents and teachers of children with ADHD

BACKGROUND

The desired (therapeutic) and undesired (side) effects of methylphenidate might have underlying correlations. The aim of this study was to explore the strength and the possible sources of these correlations.

METHODS

One hundred and fifty-seven children with ADHD (6-12 years) were administered placebo and methylphenidate (0.5 mg/kg in a divided b.i.d. dose), each for a one-week period, in a double-blind, crossover trial. Therapeutic response was assessed using the Conners' Global Index for parents (CGI-Parents) and teachers (CGI-Teachers), while side effects were assessed using the Barkley Side Effects Rating Scale (SERS).

RESULTS

The side effect profile as assessed by the SERS was similar to that of previous studies with insomnia, decreased appetite, and headaches showing significant treatment effects (p < 0.005). These "somatic/physical" side effects did not correlate with CGI-Parents or CGI-Teachers. However, the side effects of "irritability", "proneness to crying", and "anxiousness" showed significant relationships with CGI-Parents. These "mood/anxiety" side effects showed no significant correlations with the CGI-Teachers.

CONCLUSION

The greater "mood/anxiety" side effects on methylphenidate and placebo, the less the parents observe improvement of their children while treated with methylphenidate. This suggests that the correlations between "mood/anxiety" side effects and poor response to treatment may be driven by observer effects rather than biological commonalities between therapeutic and side effects of methylphenidate.

A preliminary study on the effect of methylphenidate on motor performance in children with comorbid DCD and ADHD

Attention Deficit Hyperactive Disorder (ADHD) and Developmental Coordination Disorder (DCD) are two developmental disorders with considerable comorbidity. The impact of Methylphenidate (MPH) on ADHD symptoms is well documented. However, the effects of MPH on motor coordination are less studied. We assessed the influence of MPH on motor performance of children with comorbid DCD and ADHD. Participants were 18 children (13 boys, mean age 8.3 years) diagnosed with comorbid DCD and ADHD. A structured clinical interview (K-SADS-PL) was used to determine psychopathology and the Movement Assessment Battery for Children-Checklist were used to determine criterion for motor deficits. The Movement Assessment Battery for Children (M-ABC) was administrated to all participants once under the influence of MPH and once under a placebo pill condition. The motor tests were administered on two separate days in a double-blinded design. Participants' motor performance with MPH was significantly superior to their performance in the placebo condition. Significant improvement was observed in all the M-ABC sub-tasks except for static balance performance. The findings suggest that MPH improves motor coordination in children with comorbid DCD and ADHD but clinically significant improvement was found in only 33% of the children.

Subtypes of aggression in children with attention deficit hyperactivity disorder: medication effects and comparison with typical children

We examined aggressive behavior in 6- to 12-year-old children, including 20 children with attention deficit hyperactivity disorder (ADHD) on stimulant medication, 19 children with ADHD on placebo (n = 19), and 32 controls. Children completed a laboratory provocation task designed to measure hostile, instrumental, reactive, and proactive aggression. Children in the ADHD-placebo group exhibited increased proactive and reactive aggression following high levels of provocation compared to controls. On the last trials, instrumental aggression dissipated for controls and hostile aggression dissipated for children in the ADHD-placebo group. Both instrumental and hostile aggression dissipated for children in the ADHD-medication group.

Inhibition of mitochondrial respiratory chain in the brain of adult rats after acute and chronic administration of methylphenidate

Methylphenidate (MPH) is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. It was previously demonstrated that MPH altered brain metabolic activity. Most cell energy is obtained through oxidative phosphorylation, in the mitochondrial respiratory chain. However, there are still few studies about MPH effects on the brain of adult rats. Thus, in the present study we evaluated the effect of acute or chronic administration of MPH on the activities of mitochondrial respiratory chain complexes I-IV in the brain of adult rats. For acute administration, a single injection of MPH was given to 60-day-old rats. For chronic administration, MPH injections were given to 60-day-old rats once daily for 28 days. Our results showed that complexes I, II, III and IV were inhibited after acute or chronic MPH administration in the hippocampus, prefrontal cortex, striatum and cerebral cortex. On the other hand, cerebellum was not affected.

Association of the dopamine transporter gene and ADHD symptoms in a Canadian population-based sample of same-age twins

Attention deficit hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder emerging during childhood. Psychostimulant medications (e.g., methylphenidate) noticeably reduce ADHD symptoms in most children. Since methylphenidate inhibits dopamine transporter activity, the dopamine transporter gene (DAT1) was considered to be the prime candidate risk gene in ADHD. Several studies found evidence for an association between the 10-repeat allele of the variable number of tandem repeat (VNTR) located in the 3' untranslated region and ADHD and/or ADHD symptoms in clinical and population-based samples. However, this finding was not replicated in all samples. In this study, we investigated the association between the DAT1 gene and ADHD symptoms in a population-based twin sample from Québec (Canada). We used two polymorphisms, the VNTR and rs27072, the last providing the most significant results in a clinical sample from Toronto (Ontario, Canada). No association was noted between the VNTR and ADHD symptoms in children at 6 and 7 years of age, as reported by teachers. However, a significant association was found for the rs27072 polymorphism and symptoms of inattention and hyperactivity/impulsivity. These findings indicate that the DAT1 gene contributes to ADHD symptoms in this sample and further suggest that the VNTR may not be the optimal polymorphism for study in all populations.

Methylphenidate increases creatine kinase activity in the brain of young and adult rats

AIMS

The high prevalence of Attention Deficit/Hyperactivity Disorder (ADHD) and the increased therapeutic use of methylphenidate (MPH) raise some concerns regarding its long-term side effects and safety profile. Considering that MPH effects on brain metabolism are poorly known and that creatine kinase (CK) plays an important role in cell energy homeostasis, we evaluated CK activity in the brain of young and adult rats following acute (one injection) or chronic (28 days) administration of MPH.

MAIN METHODS

MPH was acutely or chronically administered to young and adult rats. For acute administration, a single injection of MPH was given to rats on postnatal day (PD) 25 or PD 60, in the young and adult groups, respectively. For chronic administration, MPH injections were given to young rats starting at PD 25 once daily for 28 days (last injection at PD 53). In adult rats, the same regimen was performed starting at PD 60 (last injection at PD 88). CK activity was measured in brain homogenates.

KEY FINDINGS

Our results showed that MPH acute administration increased the enzyme in prefrontal cortex, hippocampus, striatum and cerebral cortex, but not cerebellum of young and adult rats. Chronic administration of MPH also increased CK activity in these brain regions, as well as the cerebellum, in young and adult rats. The highest dose (10.0 mg/kg) presented more pronouncing effects.

SIGNIFICANCE

The present findings suggest that acute or chronic exposure to MPH increased CK activity, an enzyme involved in energy homeostasis, in the brain of young and adult rats.

Chronic administration of methylphenidate activates mitochondrial respiratory chain in brain of young rats

Methylphenidate is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. Psychostimulants can cause long-lasting neurochemical and behavioral adaptations. The exact mechanisms underlying its therapeutic and adverse effects are still not well understood. In this context, it was previously demonstrated that methylphenidate altered brain metabolic activity, evaluated by glucose consumption. Most cell energy is obtained through oxidative phosphorylation, in the mitochondrial respiratory chain. Tissues with high energy demands, such as the brain, contain a large number of mitochondria. In this work, our aim was to measure the activities of mitochondrial respiratory chain complexes II and IV and succinate dehydrogenase in cerebellum, prefrontal cortex, hippocampus, striatum, and cerebral cortex of young rats (starting on 25th post-natal day and finishing on 53rd post-natal day) chronically treated with methylphenidate. Our results showed that mitochondrial respiratory chain enzymes activities were increased by chronic administration of this drug. Succinate dehydrogenase was activated in cerebellum, prefrontal cortex and striatum, but did not change in hippocampus and brain cortex. Complex II activity was increased in cerebellum and prefrontal cortex and was not affected in hippocampus, striatum and brain cortex. Finally, complex IV activity was increased in cerebellum, hippocampus, striatum and brain cortex, and was not affected in prefrontal cortex. These findings suggest that chronic exposure to methylphenidate in young rats increases mitochondrial enzymes involved in brain metabolism. Further research is being carried out in order to better understand the effects of this drug on developing nervous system and the potential consequences in adulthood resulting from early-life drug exposure.

Child mental health and human capital accumulation: the case of ADHD

One in five U.S. youngsters has a mental disorder, but we know little about the effects of these disorders on child outcomes. We examine U.S. and Canadian children with symptoms of Attention Deficit Hyperactivity Disorder (ADHD), the most common child mental health problem. Our innovations include the use of nationally representative samples of children, the use of questions administered to all children rather than focusing only on diagnosed cases, and the use of sibling fixed effects to control for omitted variables. We find large negative effects on test scores and schooling attainment suggesting that mental health conditions are a more important determinant of average outcomes than physical health conditions.

Osmotic, controlled-release methylphenidate for the treatment of ADHD

Methylphenidate (MPH) is the most commonly used and best-studied stimulant medication for attention-deficit hyperactivity disorder. However, its short duration of action usually results in a requirement to administer multiple daily doses in order to achieve optimal clinical benefit. Although a wax-matrix-based SR formulation of MPH has been available since the 1990s, it was not well accepted into clinical practice. The variable absorption profile and lack of an immediate-release component results in a slower onset of action compared with immediate-release MPH. Hence, there was a need to develop alternative longer-lasting preparations of MPH that were as efficacious as IR MPH, but which also addressed the problems inherent in multiple daily dosing. An osmotic, controlled-release (OROS) formulation of MPH HCl has been developed over the past 10 years for once-daily administration. OROS MPH has been widely accepted by clinicians and is now the most widely prescribed MPH product in North America. Clinical trials have shown OROS MPH to have a continued action over a 12-h period, to be superior to placebo and to be as effective as immediate-release MPH dosed three times daily, in reducing symptoms of attention-deficit hyperactivity disorder, with similar incidence of side effects. There have been a smaller number of trials comparing OROS MPH with non-stimulant treatments, such as atomoxetine.

The laboratory school protocol: its origin, use, and new applications

OBJECTIVE

ADHD is the most common childhood psychiatric disorder, with impairments seen in home and academic settings. To investigate such impairments in a school-like setting, the laboratory school protocol (LSP) was developed at the University of California, Irvine.

METHOD

This model provides a rigorously controlled environment to examine pharmacodynamic and pharmacokinetic aspects of responses to treatment. A key principle of this methodology is to exercise tight control of the timing and context of measurements by establishing a cycle of activities repeated across each study day. In addition, the LSP approach has been extended to both younger and older populations than the typically studied school-aged group. This extension requires corresponding modifications in measures to characterize drug efficacy and to allow evaluation of ADHD symptoms in a highly standardized setting.

RESULTS

This article provides guidelines for employing the LSP for the assessment of medication effects for both preschool and adolescent/adult populations.

CONCLUSION

The LSP can be modified to form either an Adult Workplace Environment or a Preschool Assessment Laboratory.

Visual function and ocular features in children and adolescents with attention deficit hyperactivity disorder, with and without treatment with stimulants

AIMS

To investigate visual function and ocular features in children with attention deficit hyperactivity disorder (AD/HD) and establish whether treatment with stimulants is reflected in functioning of the visual system.

METHODS

Detailed ophthalmologic evaluations without and with stimulants were performed in 42 children (37 boys) with AD/HD, mean age 12 years, and compared with a reference group (ref; n=50; mean age 11.9 years; 44 boys). For a comparison between two groups, Mann-Whitney's U-test was used for ordered and continuous variables; for dichotomous variables, Fisher's exact test was used. For paired comparison (with and without treatment), sign test was used.

RESULTS

In all, 83% had visual acuity of >0.8 (<0.1 logMAR) without treatment, 90% with stimulants (ref 98%; P=0.032 and n.s., respectively). Heterophoria was found in 29% without, and in 27% with, stimulants (ref 10%; P=0.038 and n.s., respectively) and subnormal stereovision (>60 s of arc) in 26% (ref 6%; P=0.016) without stimulants, and in 27%, with (P=0.014). Abnormal convergence (>6 cm or absent) was noted in 24% (ref 6%; P=0.031) without treatment and in 17%, with (n.s.). Astigmatism (> or =1.0 D) was observed in 24% (ref 6%; P=0.03), and signs of visuoperceptual problems in 21% (ref 2%; P=0.007). We found smaller optic discs (n=8/38) and neuroretinal rim areas (n=7/38) (P<0.0001) and decreased tortuosity of retinal arteries (n=6/34) (P=0.0002) than that of controls.

CONCLUSIONS

Children with AD/HD had a high frequency of ophthalmologic findings, which were not significantly improved with stimulants. They presented subtle morphological changes of the optic nerve and retinal vasculature, indicating an early disturbance of the development of these structures.

Methylphenidate treatment induces oxidative stress in young rat brain

Methylphenidate (MPH) is frequently prescribed for the treatment of attention deficit/hyperactivity disorder. Psychostimulants can cause long-lasting neurochemical and behavioral adaptations. Here, we evaluated oxidative damage in the rat brain and the differential age-dependent response to MPH after acute and chronic exposure. We investigated the oxidative damage, assessed by the thiobarbituric acid reactive species (TBARS), and the protein carbonyl assays in cerebellum, prefrontal cortex, hippocampus, striatum, and cerebral cortex of young (25 days old) and adult (60 days old) male Wistar rats after acute and chronic exposure to MPH. Chronic MPH-treated young rats presented a dose-dependent increase in TBARS content and protein carbonyls formation in specific rat brain regions. In the acute exposure, only MPH highest dose increased lipid peroxidation in the hippocampus. No difference in protein carbonylation was observed among groups in all structures analyzed. In adult rats, we did not find oxidative damage in both acute and chronic treatment. Chronic exposure to MPH in induces oxidative damage in young rat brain, differentially from chronic exposure during adulthood. These findings highlight the need for further research to improve understanding of MPH effects on developing nervous system and the potential consequences in adulthood resulting from early-life drug exposure.

Stimulant actions in rodents: implications for attention-deficit/hyperactivity disorder treatment and potential substance abuse

Most evidence supports the continued use of stimulants as the best available pharmacotherapy for the treatment of children with attention-deficit/hyperactivity disorder (ADHD), but little is known about possible enduring behavioral and neuroadaptational consequences of long-term stimulant exposure. Although a variety of preclinical studies, particularly those using methylphenidate (MP), have attempted to address these issues, most of these studies have used procedures that might not adequately simulate clinical treatment conditions, and results have not been entirely consistent. In particular, the rationale for selection of MP doses that simulate clinical exposure has not been well defined. We suggest that the use of more appropriate treatment conditions, including doses that result in plasma drug levels comparable to therapeutic levels, will provide a more accurate model for adequately assessing the therapeutic mechanisms and potential long-term consequences of stimulant psychotherapy in the treatment of ADHD.

Transdermal methylphenidate, behavioral, and combined treatment for children with ADHD

Stimulant medication and behavioral treatments are evidence-based for children with attention-deficit/hyperactivity disorder, but the combination of the 2 treatments has been understudied. In this investigation, methylphenidate (MPH) was crossed with 2 levels of behavior modification (BMOD) in a summer treatment program. Twenty-seven children with attention-deficit/hyperactivity disorder, aged 6-12, participated. Children received placebo and 3 doses of transdermal MPH (12.5 cm(2), 25.0 cm(2), and 37.5 cm(2)). BMOD was implemented on alternating weeks. Both treatments produced large and significant effects. Combined treatment was superior to either treatment alone. The effects of transdermal MPH were comparable to those found in this setting in previous studies with multiple stimulant medications and formulations. Consistent with other research, low doses of MPH--even lower than in previous studies--yielded enhanced effects in combination with behavior modification.

Sleep in children with attention-deficit hyperactivity disorder (ADHD): a review of naturalistic and stimulant intervention studies

Attention-Deficit Hyperactivity Disorder (ADHD) is the most common behavioral disorder of childhood. Multiple clinical and research reports suggest extensive sleep disturbances in children with ADHD, however, current data is contradictory. This paper reviewed 47 research studies (13 stimulant intervention and 34 naturalistic) on ADHD that were published since 1980. The main objectives of this review were to provide pediatric clinicians and researchers a clear and concise summary of published sleep data in children with ADHD, to provide a more accurate description of the current knowledge of the relationship between sleep and ADHD, and to provide current information on the effect of stimulant medication on sleep. Twenty-five of the reviewed studies used subjective reports of sleep, six were actigraphic studies, and 16 were overnight polysomnographic sleep studies (two of which also included Multiple Sleep Latency Tests). All participants were between the age of 3 and 19, and 60% were male. The results indicate high rates of parental reports of sleep disturbances in medicated and unmedicated children with ADHD, however, the majority of these findings have not been confirmed by objective sleep data. Although, agreement among objective studies is not absolute, the data suggest increased nighttime activity, reduced rapid eye movement sleep, and significant daytime somnolence in unmedicated children with ADHD when compared to controls. Data also suggest a possible increased prevalence of periodic limb movements in sleep in children with ADHD, however, little differences in sleep-disordered breathing. The limited number of studies, small and heterogeneous samples, and other methodological limitations make definite results difficult to determine. Future research will need to further clarify the relationship between sleep and ADHD and the effects of stimulants on sleep of children with ADHD.

Aufmerksamkeitsdefizit- und Hyperaktivitätsstörungen (ADHD) im Kindesalter

Zusammenfassung. ADHD hat sich in den letzten Jahren zu einer populären pädiatrischen Diagnose mit Prävalenzraten von bis zu 17 % entwickelt, die zudem auf ein außerordentlich hohes öffentliches und wissenschaftliches Interesse stößt. Bei einer systematischen Sichtung von Erklärungs- und Veränderungsmodellen fällt eine große Inkonsistenz der Befunde auf und ein integrierendes Metamodell als Grundlage für systematische Interventionen ist bisher nicht erkennbar. In einem ersten Schritt haben wir daher versucht, die heterogenen Befunde in eine Modifikation des Salutogenesemodells von Antonovsky einzuordnen und hieraus Leitideen für gezielte Interventionen abzuleiten. Eine Durchführung und Evaluation von Interventionen, die auch das störungsspezifische Merkmal des auffälligen Bewegungsverhaltens mit berücksichtigen, haben wir in mehreren Pilotstudien mit insgesamt n=26 Kindern verfolgt, wobei mäßige Ergebnisse in der Veränderung von Parametern der Aufmerksamkeit und geringe Veränderungen in der motorischen Leistungsfähigkeit erzielt wurden. Für weitere Interventionsstudien wird daher vorgeschlagen, genauer die gezielte Beeinflussung der motorischen Leistungsfähigkeit in Anlehnung an das kognitiv-energetische Modell von Sanders zu verfolgen.

The use of a laboratory school protocol to evaluate concepts about efficacy and side effects of new formulations of stimulant medications

Recently, new long-acting formulations of racemic methylphenidate (MPH: Ritalin LA, Metadate CD and Concerta) and amphetamine (AMP: Adderall XR) were developed and are now approved by the Food and Drug Administration (FDA). In addition, dexmethylphenidate (Focalin), the pharmacologically active d-threo enantiomer of MPH, also was approved by the FDA. In the initial phases of development, prototypes of these five new formulations were evaluated using the University of California, Irvine (UCI) Laboratory School Protocol (LSP), in which surrogate measures of efficacy are collected in highly controlled settings rather than clinical measures of effectiveness in the less-controlled, natural environments of home or school. The LSP studies were followed by large effectiveness and safety studies required for gaining FDA approval. These initial efficacy and side effect studies in the LSP provided missing information about the basic pharmacokinetic (PK) and pharmacodynamic (PD) properties of MPH and AMP and produced some new discoveries (i.e., acute tolerance) that were used to help design the final products. The final once-a-day formulations used different drug delivery systems to achieve long-acting efficacy (Ritalin LA, Metadate CD, Concerta, Adderall XR). All four drug delivery systems were based on two processes: first, a bolus delivery (BD) process to achieve rapid onset of efficacy (mg), and second, a controlled delivery (CD) process to achieve rates of delivery (mg/hr) or a delayed bolus (mg) to maintain efficacy. A theoretical approach was used to compare and contrast the new once-a day formulations of MPH by selecting total daily doses (mg/d) that would equate drug delivery by the first process (mg of the initial bolus) and the second process (mg/hr over specified time period). In addition to efficacy, applications of the LSP to measure common side effects related to eating and sleeping were described and discussed.

Pharmacokinetic and pharmacodynamic properties of stimulants: implications for the design of new treatments for ADHD

In the USA, the stimulant drug methylphenidate (MPH) is used to treat a large number (2 million or more per year) of children with Attention Deficit Hyperactivity Disorder (ADHD). Although the US FDA approved MPH in the 1960s, the pharmacokinetic (PK) properties of serum concentrations of MPH in children with ADHD were not described until the 1980s, and then in only a few cases. Recently, information from drug development programs have increased our knowledge about the serum PK and some pharmacodynamic (PD) characteristics of MPH in ADHD children, and studies based on positron emission tomograpy (PET) in adult volunteers have provided new knowledge about the PK properties of MPH at the primary site of action in the brain. We will review these two topics and use this new information to evaluate the mechanisms of action of MPH.

Oculomotor abnormalities in attention deficit hyperactivity disorder: a preliminary study

BACKGROUND

Prevailing hypotheses suggest that attention deficit hyperactivity disorder (ADHD) is secondary to dysfunction of motor intentional systems mediated by prefrontal circuitry. Oculomotor paradigms provide a mechanism for examining and localizing dysfunction at the interface between movement and cognition.

OBJECTIVE

Three different saccade tasks (reflexive or prosaccades, antisaccades, and memory-guided saccades) were used to examine functions necessary for the planning and the execution of eye movements, including motor response preparation, response inhibition, and working memory.

METHODS

The study included 19 children with ADHD, divided into two groups: a group of 8 children on methylphenidate at the time of testing and a group of 11 children not taking any psychoactive medication. Results from the two groups were compared with those from 25 age- and gender-matched normal control children.

RESULTS

Both groups of children with ADHD made significantly more directional errors than did controls on the antisaccade task and significantly more anticipatory errors than did controls on the memory-guided saccade task, findings that are consistent with deficits in response inhibition. There were no significant differences in prosaccade latency, although unmedicated children with ADHD showed significantly greater variability in latency on the prosaccade task than did controls. On the memory-guided saccade task there were no significant differences in saccade accuracy; however, unmedicated children with ADHD showed longer saccade latency than did either controls or medicated children with ADHD.

CONCLUSIONS

Oculomotor findings suggest that deficits in prefrontal functions, in particular response inhibition, contribute to behavioral abnormalities observed in ADHD. Findings also suggest that the administration of methylphenidate is associated with improvements in the consistency of motor response. Although there were no observed improvements in response inhibition with methylphenidate, conclusions await a design in which subjects complete testing both on and off medication.