Developmental milestones and daily living skills in individuals with Angelman syndrome.

BACKGROUND: Angelman syndrome (AS) is a neurodevelopmental disorder associated with severe global developmental delay. However, the ages at which different developmental skills are achieved in these individuals remain unclear. We seek to determine the probability and the age of acquisition of specific developmental milestones and daily living skills in individuals with AS across the different molecular subtypes, viz. class I deletion, class II deletion, uniparental disomy, imprinting defect, and UBE3A variants. METHODS: Caregivers participating in a longitudinal multicenter Angelman Syndrome Natural History Study completed a questionnaire regarding the age at which their children achieved specific developmental milestones and daily living skills. The Cox Proportional Hazard model was applied to analyze differences in the probability of achievement of skills at various ages among five molecular subtypes of AS. RESULTS: Almost all individuals, regardless of molecular subtype, were able to walk with support by five years of age. By age 15, those with a deletion had at least a 50% probability of acquiring 17 out of 30 skills compared to 25 out of 30 skills among those without a deletion. Overall, fine and gross motor skills such as holding and reaching for small objects, sitting, and walking with support were achieved within a fairly narrow range of ages, while toileting, feeding, and hygiene skills tend to have greater variability in the ages at which these skills were achieved. Those without a deletion had a higher probability (25-92%) of achieving daily living skills such as independently toileting and dressing compared to those with a deletion (0-13%). Across all molecular subtypes, there was a low probability of achieving independence in bathing and brushing teeth. CONCLUSION: Individuals with AS without a deletion are more likely to achieve developmental milestones and daily living skills at an earlier age than those with a deletion. Many individuals with AS are unable to achieve daily living skills necessary for independent self-care.

Lymphocytic Extracellular Signal-Regulated Kinase Dysregulation in Autism Spectrum Disorder.

OBJECTIVE: Extracellular signal-regulated kinase (ERK1/2) is a conserved central intracellular signaling cascade involved in many aspects of neuronal development and plasticity. Converging evidence support investigation of ERK1/2 activity in autism spectrum disorder (ASD). We previously reported enhanced baseline lymphocytic ERK1/2 activation in autism, and now we extend our work to investigate the early phase kinetics of lymphocytic ERK1/2 activation in idiopathic ASD. METHOD: Study participants included 67 individuals with ASD (3-25 years of age), 65 age- and sex-matched typical developing control (TDC) subjects, and 36 age-, sex-, and IQ-matched developmental disability control (DDC) subjects matched to those with ASD and IQ <90. We completed an additional analysis comparing results from ASD, TDC, and DDC groups with data from 37 individuals with Fragile X syndrome (FXS). All subjects had blood lymphocyte samples analyzed by flow cytometry following stimulation with phorbol ester and sequentially analyzed for ERK1/2 activation (phosphorylation) at several time points. RESULTS: The ASD group (mean = 5.81 minutes; SD = 1.5) had a significantly lower (more rapid) mean ERK1/2 T1/2 activation value than both the DDC group (mean = 6.78 minutes; SD = 1.6; p = .00078) and the TDC group (mean = 6.4 minutes; SD = 1.5; p = .025). More rapid ERK1/2 T1/2 activation times did correlate with increased social impairment across all study groups including the ASD cohort. Differences in ERK1/2 T1/2 activation were more pronounced in younger than in older individuals in the primary analysis. The ASD group additionally had more rapid activation times than the FXS group, and the FXS group activation kinetics did not differ from those of the TDC and DDC groups. CONCLUSION: Our findings indicate that lymphocytic ERK1/2 activation kinetics are dysregulated in persons with ASD, marked by more rapid early phase activation. Group differences in ERK1/2 activation kinetics appear to be driven by findings from the youngest children analyzed. DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We actively worked to promote sex and gender balance in our author group. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.

Brief Report: Intranasal Ketamine in Adolescents and Young Adults with Autism Spectrum Disorder-Initial Results of a Randomized, Controlled, Crossover, Pilot Study.

Dysregulation of glutamate neurotransmission plays a critical role in autism spectrum disorder (ASD) pathophysiology and is a primary target for core deficit research treatment trials. The mechanism of action of ketamine has striking overlap with the theory of ASD as a disorder of synaptic communication and neuronal networks. This two-dose, double-blind, placebo controlled, cross-over pilot trial of intranasal (IN) ketamine targeting core social impairment included individuals with ASD (N = 21) between 14 and 29 years. Participants were randomized to received two doses of IN ketamine (30 and 50 mg) and two doses of matching placebo. No significant impact was noted on the Aberrant Behavior Checklist Social Withdraw subscale. The IN ketamine was well tolerated, with only transient mild adverse effects.

Recent Advances in the Pharmacological Management of Behavioral Disturbances Associated with Autism Spectrum Disorder in Children and Adolescents.

Autism spectrum disorder (ASD) is a heterogeneous neuropsychiatric condition affecting an estimated one in 36 children. Youth with ASD may have severe behavioral disturbances including irritability, aggression, and hyperactivity. Currently, there are only two medications (risperidone and aripiprazole) approved by the US Food and Drug Administration (FDA) for the treatment of irritability associated with ASD. Pharmacologic treatments are commonly used to target ASD-associated symptoms including irritability, mood lability, anxiety, and hyperactivity. However, evidence for the efficacy of many commonly used treatments is limited by the lack of large placebo-controlled trials of these medications in this population. Research into the pathophysiology of ASD has led to new targets for pharmacologic therapy including the neuroimmune system, the endocannabinoid system, and the glutamatergic neurotransmitter system. The goal of this review is to provide an overview of the current evidence base for commonly used treatments, as well as emerging treatment options for common behavioral disturbances seen in youth with ASD.

Pediatric Quality of Life Inventory (PedsQL) in Fragile X Syndrome.

To date, health related quality of life (QoL) has not been systematically evaluated in youth with fragile X syndrome (FXS), the most common single gene cause of autism and the most common inherited form of developmental disability. We describe QoL data gathered using the Pediatric Quality of Life Inventory (PedsQL) completed online by 364 parents of youth with FXS. Parents consistently reported across all gender and age groups that their children experienced the highest QoL in Physical functioning and the lowest QoL in Cognitive functioning. Overall, older children with FXS had increase QoL ratings in the domains of School and Cognitive function.

Motor cortex facilitation: a marker of attention deficit hyperactivity disorder co-occurrence in autism spectrum disorder.

The neural correlates distinguishing youth with Autism Spectrum Disorder (ASD-) and ASD with co-occurring Attention Deficit Hyperactivity Disorder (ASD+) are poorly understood despite significant phenotypic and prognostic differences. Paired-pulse transcranial magnetic stimulation (TMS) measures, including intracortical facilitation (ICF), short interval cortical inhibition (SICI), and cortical silent period (CSP) were measured in an age matched cohort of youth with ASD- (n = 20), ASD + (n = 29), and controls (TDC) (n = 24). ASD- and ASD+ groups did not differ by IQ or social functioning; however, ASD+ had significantly higher inattention and hyperactivity ratings. ICF (higher ratio indicates greater facilitation) in ASD+ (Mean 1.0, SD 0.19) was less than ASD- (Mean 1.3, SD 0.36) or TDC (Mean 1.2, SD 0.24) (F2,68 = 6.5, p = 0.003; post-hoc tests, ASD+ vs either TDC or ASD-, p ≤ 0.05). No differences were found between groups for SICI or age corrected active/resting motor threshold (AMT/RMT). Across all ASD youth (ASD- and ASD+), ICF was inversely correlated with worse inattention (Conners-3 Inattention (r = -0.41; p < 0.01) and ADHDRS-IV Inattention percentile (r = -0.422, p < 0.01) scores. ICF remains intact in ASD- but is impaired in ASD+. Lack of ICF is associated with inattention and executive function across ASD. Taken with the present findings, ADHD may have a distinct electrophysiological "signature" in ASD youth. ICF may constitute an emerging biomarker to study the physiology of ADHD in ASD, which may align with disease prognosis or treatment response.

Pharmacologic Interventions for Irritability, Aggression, Agitation and Self-Injurious Behavior in Fragile X Syndrome: An Initial Cross-Sectional Analysis.

Using a dataset involving 415 individuals with irritability, aggression, agitation and self-injury (IAAS) behaviors from the fragile X syndrome (FXS) FORWARD database, we describe the psychopharmacologic management of IAAS and features of the population of persons with FXS treated with drug therapy for IAAS. Among those with FXS exhibiting IAAS, individuals with FXS receiving drug treatment of IAAS were older, more predominantly male, have more significant intellectual disability, more like to have comorbid autism, hyperarousal, and social impairments. The most commonly utilized medications for IAAS in FXS are antipsychotic medications, specifically aripiprazole and risperidone (37% and 27%, respectively). The majority of subjects (63%) experienced no side effects noted from the use of their psychopharmacologic medications.

Differentiating social preference and social anxiety phenotypes in fragile X syndrome using an eye gaze analysis: a pilot study.

BACKGROUND: Fragile X syndrome (FXS) is the leading inherited cause of autism spectrum disorder, but there remains debate regarding the clinical presentation of social deficits in FXS. The aim of this study was to compare individuals with FXS to typically developing controls (TDC) and individuals with idiopathic autism spectrum disorder (ASD) across two social eye tracking paradigms. METHODS: Individuals with FXS and age- and gender-matched TDC and individuals with idiopathic ASD completed emotional face and social preference eye tracking tasks to evaluate gaze aversion and social interest, respectively. Participants completed a battery of cognitive testing and caregiver-reported measures for neurobehavioral characterization. RESULTS: Individuals with FXS exhibited reduced eye and increased mouth gaze to emotional faces compared to TDC. Gaze aversive findings were found to correlate with measures of anxiety, social communication deficits, and behavioral problems. In the social interest task, while individuals with idiopathic ASD showed significantly less social preference, individuals with FXS displayed social preference similar to TDC. CONCLUSIONS: These findings suggest fragile X syndrome social deficits center on social anxiety without the prominent reduction in social interest associated with autism spectrum disorder. Specifically designed eye tracking techniques clarify the nature of social deficits in fragile X syndrome and may have applications to improve phenotyping and evaluate interventions targeting social functioning impairments.

Emotion Regulation Intensive Outpatient Programming: Development, Feasibility, and Acceptability.

Individuals with Autism Spectrum Disorder (ASD) and/or intellectual and developmental disabilities (DD) often struggle with behavior management and emotion-regulation (ER). In this manuscript, we describe the results of a chart review examining a group treatment program designed to address ER deficits in youth with ASD and/or DD. The intensive 5 week program utilizes cognitive behavior, applied behavior analysis, and mindfulness techniques and includes biweekly child and parent groups. Results indicate that this program is feasible and associated with high caregiver satisfaction. Pre-and-post outcome results indicate statistically significant improvement on behavioral measures, but did not demonstrate significant improvment on the Pediatric Quality of Life Family Impact Module. Based on overall positive outcomes, a randomized controlled trial of the program is indicated.

A Randomized Placebo-Controlled Cross-Over Pilot Study of Riluzole for Drug-Refractory Irritability in Autism Spectrum Disorder.

Riluzole is a glutamatergic modulator of particular interest in autism spectrum disorder (ASD). In this 12-week randomized, double-blind, placebo-controlled, crossover pilot study we evaluated the safety and tolerability of 5-week of adjunctive riluzole treatment (vs. 5-week of placebo, with 2-week washout period) targeting ASD-associated drug-refractory irritability in eight individuals age 12-25 years. All participants tolerated riluzole 200 mg per day, however there were no statistically significant findings for the overall treatment effect, the treatment effect by week within period of the study, or a cross-over effect across the periods of the study on the Clinical Global Impression Improvement Scale or the Aberrant Behavior Checklist Irritability subscale. The results of this trial indicate that 5-week of riluzole treatment was well tolerated, but had no significant effect on the target symptoms. Trial Registration ClinicalTrials.gov Identifier NCT02081027, Registered 5 August 2013, First participant enrolled 19 September 2013.

Risperidone Treatment for Irritability in Fragile X Syndrome.

OBJECTIVE: The goal of this study was to assess the effectiveness of risperidone monoantipsychotic therapy targeting irritability in patients with Fragile X syndrome (FXS) in a naturalistic outpatient clinical setting. METHODS: We examined the use of risperidone, predominantly in combination with other nonantipsychotic psychotropic agents, targeting irritability in 21 male patients with FXS with a retrospective analysis of a prospectively collected large developmental disabilities-specific treatment database. Mean age at start of treatment, treatment duration, final dose, body mass index (BMI), and Clinical Global Impressions-Improvement (CGI-I) Scale score at final visit were determined, and changes with treatment were analyzed using paired t-tests. RESULTS: Mean age at start of treatment was 14.0 years. The final mean dose of risperidone was 2.5 mg/day. The mean duration of treatment was 22 months. Seven (33.33%) participants were considered treatment responders based on the CGI-I. Change in BMI between initiation and cessation of treatment episode was not significant, however, these data were only available for a subset (n = 11) of patients. CONCLUSIONS: Risperidone may be effective in the treatment of irritability in males with FXS. The overall effectiveness of monoantipsychotic treatment with risperidone was limited in this study compared with previous published reports; however, this may be the result of differences in outcome measures as well as a reflection of the level of functioning and severity of irritability in this sample.

A randomized controlled trial of levodopa in patients with Angelman syndrome.

Treatment for Angelman syndrome (AS) is currently limited to symptomatic interventions. A mouse model of AS has reduced calcium/calmodulin-dependent kinase II activity due to excessive phosphorylation of specific threonine residues, leading to diminished long-term potentiation. In a rat model of Parkinson disease, levodopa reduced phosphorylation of various proteins, including calcium/calmodulin-dependent kinase II. Further studies demonstrated that AS mice treated with levodopa performed better on rotarod testing than untreated AS mice. We conducted a multi-center double-blind randomized placebo-controlled 1-year trial of levodopa / carbidopa with either 10 or 15 mg/kg/day of levodopa in children with AS. The outcome of this intervention was assessed using either the Bayley Scales of Infant Development or the Mullen Scales of Early Learning, as well as the Vineland Adaptive Behavior Scales, and the Aberrant Behavior Checklist. Of the 78 participants enrolled, 67 participants received study medication (33 on levodopa, 34 on placebo), and 55 participants (29 on levodopa, 26 on placebo) completed the 1-year study. There were no clinically or statistically significant changes in any of the outcome measures over a 1-year period comparing the levodopa and placebo groups. The number of adverse events reported, including the more serious adverse events, was similar in both groups, but none were related to treatment with levodopa. Our data demonstrate that levodopa is well-tolerated by children with AS. However, in the doses used in this study, it failed to improve their neurodevelopment or behavioral outcome.

Characterization of Medication Use in a Multicenter Sample of Pediatric Inpatients with Autism Spectrum Disorder.

Nearly 11% of youth with Autism Spectrum Disorder (ASD) undergo psychiatric hospitalization, and 65% are treated with psychotropic medication. Here we characterize psychotropic medication usage in subjects enrolled in the Autism Inpatient Collection. Participant psychotropic medication usage rates topped 90% at admission and discharge, though there was a decline at 2-month follow-up. Antipsychotics, ADHD medications, and sleep aids were the most commonly reported classes of medications. The impact of age, gender, and non-verbal IQ on medication usage rates was minimal, though age and IQ may play a role in prescribing practices. Future work is indicated to explore medication usage trends, the impact of clinical factors on medication use rates, and the safety of psychotropic medications in youth with ASD.

Lurasidone for the treatment of irritability and anger in autism spectrum disorders.

INTRODUCTION: Autism Spectrum Disorder (ASD) is a heterogeneous neurodevelopmental disorder characterized by deficits in social interaction and communication as well as restricted patterns of behaviors and interests. Irritability marked by tantrums, self-injury and aggression occurs frequently in youth with ASD, causing significant parent and caregiver distress. Atypical antipsychotics have been the most studied drug class targeting irritability in ASD. Risperidone and aripiprazole are Food and Drug Administration (FDA)-approved atypical antipsychotics for treatment of irritability in youth with ASD. However, other atypical antipsychotics, such as lurasidone, are often considered for off-label use in the treatment of irritability, whether because of tolerability issues with risperidone and aripiprazole or because of the drug-refractory nature of this symptom cluster. Areas covered: Following a comprehensive review of the literature this article summarizes information on the efficacy and tolerability of lurasidone as a potential off label treatment of irritability in children and adolescents with ASD. Available data included a 6 week randomized, blind, fixed dose, placebo-controlled study and a case study. Expert opinion: To date the safety and tolerability of lurasidone in treating irritability in youth with ASD has yet to be established with, lurasidone being the only antipsychotic with published negative placebo-controlled results.

Eye gaze and pupillary response in Angelman syndrome.

BACKGROUND: Angelman syndrome (AS) is a rare neurological disorder characterized by severe developmental disability, communication impairment, elevated seizure risk, and motor system abnormalities. AIMS: The aims of this study were to determine the feasibility of social scene eye tracking and pupillometry measures in individuals with AS and to compare the performance of AS participants to individuals with idiopathic Autism Spectrum Disorder (ASD) and typically developing controls (TDC). METHODS AND PROCEDURES: Individuals with AS and age- and gender- matched controls completed a social eye tracking paradigm. Neurobehavioral characterization of AS participants was completed via a battery of psychological testing and caregiver behavioral evaluations. OUTCOMES AND RESULTS: Eight of seventeen recruited AS participants completed the eye tracking paradigm. Compared to TDC, AS subjects demonstrated significantly less preference for social scenes than geometric shapes. Additionally, AS subjects showed less pupil dilation, compared to TDC, when viewing social scenes versus geometric shapes. There was no statistically significant difference found between AS and ASD subjects in either social eye tracking or pupillometry. CONCLUSIONS AND IMPLICATIONS: The use of eye tracking and pupillometry may represent an innovative measure for quantifying AS-associated impairments in social salience.

Fragile X targeted pharmacotherapy: lessons learned and future directions.

Our understanding of fragile X syndrome (FXS) pathophysiology continues to improve and numerous potential drug targets have been identified. Yet, current prescribing practices are only symptom-based in order to manage difficult behaviors, as no drug to date is approved for the treatment of FXS. Drugs impacting a diversity of targets in the brain have been studied in recent FXS-specific clinical trials. While many drugs have focused on regulation of enhanced glutamatergic or deficient GABAergic neurotransmission, compounds studied have not been limited to these mechanisms. As a single-gene disorder, it was thought that FXS would have consistent drug targets that could be modulated with pharmacotherapy and lead to significant improvement. Unfortunately, despite promising results in FXS animal models, translational drug treatment development in FXS has largely failed. Future success in this field will depend on learning from past challenges to improve clinical trial design, choose appropriate outcome measures and age range choices, and find readily modulated drug targets. Even with many negative placebo-controlled study results, the field continues to move forward exploring both the new mechanistic drug approaches combined with ways to improve trial execution. This review summarizes the known phenotype and pathophysiology of FXS and past clinical trial rationale and results, and discusses current challenges facing the field and lessons from which to learn for future treatment development efforts.

Brief Report: Metformin for Antipsychotic-Induced Weight Gain in Youth with Autism Spectrum Disorder.

Antipsychotic treatment in youth with autism spectrum disorder (ASD) is becoming increasingly common, placing individuals at risk for antipsychotic-induced weight gain and associated complications. Metformin hydrochloride, a biguanide medication FDA-approved for treatment of type-2 diabetes in youth, may hold promise for treatment of antipsychotic-induced weight gain in youth with ASD. In this report we assess the long-term impact of metformin on antipsychotic-associated weight gain in a naturalistic sample of 53 youth with ASD. Results indicate that treatment with metformin stabilized BMI z-score over a nearly 2 year mean treatment period. Further work is indicated to determine the safety and efficacy of metformin treatment in youth with ASD, as well as predictors of response as a treatment for antipsychotic-induced weight gain.

d-Cycloserine enhances durability of social skills training in autism spectrum disorder.

BACKGROUND: d-Cycloserine (DCS) enhances extinction learning across species, but it has proven challenging to identify consistent benefit of DCS when added to therapeutic interventions. We conducted a placebo-controlled trial of DCS to potentiate social skills training in autism spectrum disorder (ASD) but found substantial improvement in both the DCS and placebo groups at the conclusion of active treatment. Here, we assess the impact of DCS 11 weeks following active treatment to evaluate the impact of DCS on treatment response durability. METHODS: Study participants included 60 outpatient youth with ASD, ages 5-11 years, all with IQ above 70, and significantly impaired social functioning who completed a 10-week active treatment phase during which they received weekly single doses of 50 mg of DCS or placebo administered 30 min prior to group social skills training. Following the 10-week active treatment phase, blinded follow-up assessments occurred at week 11 and week 22. The primary outcome measure for our durability of treatment evaluation was the parent-rated social responsiveness scale (SRS) total raw score at week 22. RESULTS: Analysis of the SRS total raw score demonstrated significant decrease for the DCS group compared to the placebo group (p = 0.042) indicating greater maintenance of treatment effect in the DCS group. DCS was well tolerated, with irritability being the most frequently reported adverse effect in both groups. CONCLUSIONS: The findings of this study suggest that DCS may help youth with ASD to maintain skills gained during sort-term social skills training. Larger-scale studies with longer follow-up will be necessary to further understand the long-term impact of DCS paired with structured social skills training. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01086475.

Multiple Antipsychotic Medication Use in Autism Spectrum Disorder.

OBJECTIVE: The purpose of this study was to explore the use of multiple antipsychotic medications in patients with autism spectrum disorder (ASD) by reviewing the longitudinal medication management of 1100 patients consecutively treated for behavioral symptoms associated with ASD at a tertiary care specialty clinic. METHODS: We identified all patients with ASD treated with daily doses of two or more antipsychotics for at least two visits at our clinic. For each patient meeting inclusion criteria, diagnostic and demographic data were collected. To evaluate clinical need and effectiveness of antipsychotic medications in this sample, we reviewed symptoms targeted with each antipsychotic medication and concomitant medications prescribed. Clinical Global Impressions-Severity (CGI-S) and Clinical Global Impressions-Improvement (CGI-I) scale ratings had been completed at the time of each visit, and the duration of treatment with antipsychotic medications was determined. To evaluate the safety and tolerability of antipsychotic medication use in ASD, we reviewed reported adverse effects and calculated body mass index (BMI) change with treatment. RESULTS: Seventy patients met the inclusion criteria (6.4% of our sample). The majority of patients were moderately to severely ill Caucasian males, as determined by baseline mean CGI-S of 4.7 (SD = 0.8), and were diagnosed with autistic disorder and comorbid intellectual disability. The mean age was 15.1 years (SD = 10.9), the primary targeted symptoms were agitation/irritability, physical aggression, and self-injury. The majority of patients remained on two or more antipsychotics for >1 year. In this population, patients demonstrated greater symptomatic improvement and generally tolerated treatment without significant adverse effects. CONCLUSIONS: The use of two or more antipsychotic medications may be increasingly common in patients with ASD. This retrospective study demonstrates that this treatment approach may be of some clinical benefit, and is generally well tolerated. Prospective studies focusing on the efficacy and safety of concomitant antipsychotic medication usage in ASD should be considered.

Initial analysis of peripheral lymphocytic extracellular signal related kinase activation in autism.

BACKGROUND: Dysregulation of extracellular signal-related kinase (ERK) activity has been potentially implicated in the pathophysiology of autistic disorder (autism). ERK is part of a central intracellular signaling cascade responsible for a myriad of cellular functions. ERK is expressed in peripheral blood lymphocytes, and measurement of activated (phosphorylated) lymphocytic ERK is commonly executed in many areas of medicine. We sought to conduct the first study of ERK activation in humans with autism by utilizing a lymphocytic ERK activation assay. We hypothesized that ERK activation would be enhanced in peripheral blood lymphocytes from persons with autism compared to those of neurotypical control subjects. METHOD: We conducted an initial study of peripheral lymphocyte ERK activation in 45 subjects with autism and 26 age- and gender-matched control subjects (total n = 71). ERK activation was measured using a lymphocyte counting method (primary outcome expressed as lymphocytes staining positive for cytosolic phosphorylated ERK divided by total cells counted) and additional Western blot analysis of whole cell phosphorylated ERK adjusted for total ERK present in the lymphocyte lysate sample. RESULTS: Cytosolic/nuclear localization of pERK activated cells were increased by almost two-fold in the autism subject group compared to matched neurotypical control subjects (cell count ratio of 0.064 ± 0.044 versus 0.034 ± 0.031; p = 0.002). Elevated phosphorylated ERK levels in whole cell lysates also showed increased activated ERK in the autism group compared to controls (n = 54 total) in Western blot analysis. CONCLUSIONS: The results of this first in human ERK activation study are consistent with enhanced peripheral lymphocytic ERK activation in autism, as well as suggesting that cellular compartmentalization of activated ERK may be altered in this disorder. Future work will be required to explore the impact of concomitant medication use and other subject characteristics such as level of cognitive functioning on ERK activation. TRIAL REGISTRATION: Not applicable.