Faculty Bibliography

OBJECTIVE Nonpharmacological treatments are available for attention deficit hyperactivity disorder (ADHD), although their efficacy remains uncertain. The authors undertook meta-analyses of the efficacy of dietary (restricted elimination diets, artificial food color exclusions, and free fatty acid supplementation) and psychological (cognitive training, neurofeedback, and behavioral interventions) ADHD treatments. METHOD Using a common systematic search and a rigorous coding and data extraction strategy across domains, the authors searched electronic databases to identify published randomized controlled trials that involved individuals who were diagnosed with ADHD (or who met a validated cutoff on a recognized rating scale) and that included an ADHD outcome. RESULTS Fifty-four of the 2,904 nonduplicate screened records were included in the analyses. Two different analyses were performed. When the outcome measure was based on ADHD assessments by raters closest to the therapeutic setting, all dietary (standardized mean differences=0.21-0.48) and psychological (standardized mean differences=0.40-0.64) treatments produced statistically significant effects. However, when the best probably blinded assessment was employed, effects remained significant for free fatty acid supplementation (standardized mean difference=0.16) and artificial food color exclusion (standardized mean difference=0.42) but were substantially attenuated to nonsignificant levels for other treatments. CONCLUSIONS Free fatty acid supplementation produced small but significant reductions in ADHD symptoms even with probably blinded assessments, although the clinical significance of these effects remains to be determined. Artificial food color exclusion produced larger effects but often in individuals selected for food sensitivities. Better evidence for efficacy from blinded assessments is required for behavioral interventions, neurofeedback, cognitive training, and restricted elimination diets before they can be supported as treatments for core ADHD symptoms.

The authors systematically reviewed evidence on iron status, as well as studies of iron supplementation, in individuals with attention deficit/hyperactivity disorder (ADHD). PubMed, Ovid, EMBASE and Web of Knowledge were searched on 4 July 2012. Quantitative appraisal of trials was performed using Jadad's score. Most (n = 20) of the retrieved studies assessed an index of peripheral iron status (i.e., serum ferritin), with overall mixed results - that is, both significant and nonsignificant association between ADHD symptoms and serum ferritin levels. One MRI study reported significantly lower indices of thalamic iron in ADHD versus comparison subjects. Two trials, an open-label and a pilot randomized placebo-controlled study with high Jaded score (4), showed improvement in some but not all measures of ADHD symptoms. Three studies showed that children with ADHD plus sleep disorders, in particular restless legs syndrome, are at risk of iron deficiency. Finally, two studies suggested that iron deficiency might decrease the effectiveness of psychostimulant treatment. The authors discussed how the field could move from initial research mainly focused on serum ferritin towards a more comprehensive and translational investigation of iron in ADHD, with the potential to inform clinical practice in terms of screening and treating iron deficiency in individuals with ADHD.

This review, addressed mainly to clinicians, considers commonly asked questions related to the neuroimaging, neurophysiology, neurochemistry and genetics of Attention-Deficit/Hyperactivity Disorder (ADHD). It provides answers based on the most recent meta-analyses and systematic reviews, as well as additional relevant original studies. Empirical findings from neurobiological research into ADHD reflect a shift in the conceptualisation of this disorder from simple theoretical views of a few isolated dysfunctions to more complex models integrating the heterogeneity of the clinical manifestations of ADHD. Thus, findings from structural and functional neuroimaging suggest the involvement of developmentally abnormal brain networks related to cognition, attention, emotion and sensorimotor functions. Brain functioning alterations are confirmed by neurophysiological findings, showing that individuals with ADHD have elevated theta/beta power ratios, and less pronounced responses and longer latencies of event-related potentials, compared with controls. At a molecular level, alterations in any single neurotransmitter system are unlikely to explain the complexity of ADHD; rather, the disorder has been linked to dysfunctions in several systems, including the dopaminergic, adrenergic, serotoninergic and cholinergic pathways. Genetic studies showing a heritability of approximately 60-75% suggest that a plethora of genes, each one with a small but significant effect, interact with environmental factors to increase the susceptibility to ADHD. Currently, findings from neurobiological research do not have a direct application in daily clinical practice, but it is hoped that in the near future they will complement the diagnostic process and contribute to the long-term effective treatment of this impairing condition.

Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common childhood-onset neuropsychiatric conditions. Despite extensive research, the etiopathophysiological factors underlying ADHD are not completely understood. It has been suggested that iron deficiency may contribute to ADHD symptoms severity. Whereas evidence from studies based on serum ferritin measures, a marker of peripheral iron status, is somewhat mixed, preliminary recent evidence suggests a deficiency of brain iron in individuals with ADHD. Therefore, it has been proposed that either a deficiency of peripheral iron or a dysfunction of the blood-brain barrier, in the presence of normal peripheral iron levels, may contribute to low brain iron levels, which, in turn, would increase the risk for ADHD symptoms in a subgroup of individuals with this disorder. It has also been found that individuals with ADHD may be at increased risk of severe cardiovascular events during treatment with ADHD drugs, although the extent to which this occurs in ADHD patients compared to non-ADHD individuals is still matter of investigation. Since iron depletion has been recently reported as a risk factor for adverse prognosis in heart failure, iron deficiency might contribute both to ADHD symptoms severity before treatment and to increased risk of severe cardiovascular events during treatment with ADHD drugs in a selected subgroup of patients. Therefore, we hypothesize that the effective treatment of iron deficiency might lead both to improvement of ADHD symptoms severity and to a decrease of the risk of cardiovascular events during treatment with ADHD drugs. If empirical studies confirm this hypothesis, the clinician would be advised to systematically check iron status and effectively treat iron deficiency before starting a pharmacological treatment with ADHD drugs.

We conducted a comprehensive review of studies assessing the efficacy and tolerability of psychostimulants for ADHD-like symptoms in individuals with autism spectrum disorder (encompassing autism disorder, Asperger's syndrome and pervasive developmental disorders not otherwise specified). PubMed, Ovid, EMBASE, Web of Science, ERIC and CINHAL were searched through 3 January 2012. From a pool of 348 potentially relevant references, 12 citations (11 studies) were retained as pertinent. Four of the included studies had a randomized controlled design. Most of the studies assessed methylphenidate immediate release. Despite inter-study heterogeneity, taken together, the results of the selected reports suggest that psychostimulants may be effective for ADHD-like symptoms in autism spectrum disorder individuals. The most common adverse events reported in the included trials were appetite reduction, sleep-onset difficulties, irritability and emotional outbursts. We discuss future directions in the field, including the need for trials assessing more ecological outcomes and combined treatment strategies tailored to the specific individual features.

Although quite overlooked, increasing evidence points to a significant association between attention-deficit/hyperactivity disorder (ADHD) and obesity. Here, we present an updated systematic review and a critical discussion of studies on the relationship between ADHD and obesity, with a particular emphasis on the possible behavioral, neurobiological, and genetics underlying mechanisms. Available empirically based studies indicate that the prevalence of ADHD in clinical samples of patients seeking treatment for their obesity is higher than that in the general population. Moreover, although still limited, current evidence shows that individuals with ADHD have higher-than-average body mass index z-scores and/or significantly higher obesity rates compared with subjects without ADHD. Three mechanisms underlying the association between ADHD and obesity have been proposed: (1) obesity and/or factors associated with it (such as sleep-disordered breathing and deficits in arousal/alertness) manifest as ADHD-like symptoms; (2) ADHD and obesity share common genetics and neurobiological dysfunctions, involving the dopaminergic and, possibly, other systems (e.g., brain-derived neurotropic factor, melanocortin-4-receptor); and (3) impulsivity and inattention of ADHD contribute to weight gain via dysregulated eating patterns. With regards to the possible clinical implications, we suggest that it is noteworthy to screen for ADHD in patients with obesity and to look for abnormal eating behaviors as possible contributing factors of obesity in patients with ADHD. If further studies confirm a causal relationship between ADHD and obesity, appropriate treatment of ADHD may improve eating patterns and, as a consequence, weight status of individuals with both obesity and ADHD.

OBJECTIVE: The authors performed a comprehensive meta-analysis of task-based functional MRI studies of attention deficit hyperactivity disorder (ADHD). METHOD: The authors searched PubMed, Ovid, EMBASE, Web of Science, ERIC, CINAHAL, and NeuroSynth for studies published through June 30, 2011. Significant differences in brain region activation between individuals with ADHD and comparison subjects were detected using activation likelihood estimation meta-analysis. Dysfunctional regions in ADHD were related to seven reference neuronal systems. The authors performed a set of meta-analyses focused on age groups (children and adults), clinical characteristics (history of stimulant treatment and presence of psychiatric comorbidities), and specific neuropsychological tasks (inhibition, working memory, and vigilance/attention). RESULTS: Fifty-five studies were included (39 for children and 16 for adults). In children, hypoactivation in ADHD relative to comparison subjects was observed mostly in systems involved in executive function (frontoparietal network) and attention (ventral attentional network). Significant hyperactivation in ADHD relative to comparison subjects was observed predominantly in the default, ventral attention, and somatomotor networks. In adults, ADHD-related hypoactivation was predominant in the frontoparietal system, while ADHD-related hyperactivation was present in the visual, dorsal attention, and default networks. Significant ADHD-related dysfunction largely reflected task features and was detected even in the absence of comorbid mental disorders or a history of stimulant treatment. CONCLUSIONS: A growing literature provides evidence of ADHD-related dysfunction in multiple neuronal systems involved in higher-level cognitive functions but also in sensorimotor processes, including the visual system, and in the default network. This meta-analytic evidence extends early models of ADHD pathophysiology that were focused on prefrontal-striatal circuits.

The neuroimaging literature on attention-deficit/hyperactivity disorder (ADHD) is growing rapidly. Here, we provide a critical overview of neuroimaging studies published recently, highlighting perspectives that may be of relevance for clinicians. After a comprehensive search of PubMed, Ovid, Web of Science, and EMBASE, we located 41 pertinent papers published between January 2011 and April 2012, comprising both structural and functional neuroimaging studies. This literature is increasingly contributing to the notion that the pathophysiology of ADHD reflects abnormal interplay among large-scale brain circuits. Moreover, recent studies have begun to reveal the mechanisms of action of pharmacological treatment. Finally, imaging studies with a developmental perspective are revealing the brain correlates of ADHD over the lifespan, complementing clinical observations on the phenotypic continuity and discontinuity of the disorder. However, despite the increasing potential to eventually inform clinical practice, current imaging studies do not have validated applications in day-to-day clinical practice. Although novel analytical techniques are likely to accelerate the pace of translational applications, at the present we advise caution regarding inappropriate commercial misuse of imaging techniques in ADHD.

Abstract Objective. Brain iron deficiency has been supposed to be involved in the pathophysiology of ADHD. Available studies assessing iron in ADHD are based on serum ferritin, a peripheral marker of iron status. To what extent serum ferritin correlates with brain iron (BI) is unclear. The main aim of this study was to compare BI, estimated with magnetic resonance imaging (MRI) in the putamen, pallidum, caudate, and thalamus, between children with and without ADHD. The secondary aim was to assess the correlation between serum ferritin and BI levels. Methods. Thirty-six children (18 with and 18 without ADHD, the latter including nine healthy controls and nine psychiatric controls) completed MRI and blood sampling. Brain iron levels were estimated by imaging T2*. Results. Children with ADHD showed significantly lower estimated BI in right and left thalamus compared to healthy controls. Estimated BI did not differ significantly between children with ADHD and psychiatric controls. Children with ADHD had significantly lower levels of serum ferritin than healthy as well as psychiatric controls. Serum ferritin and T2* values did not correlate significantly in most regions. Conclusions. Low iron in the thalamus may contribute to ADHD pathophysiology.