Neuropsychological performance of youth with secondary attention-deficit/hyperactivity disorder 6- and 12-months after traumatic brain injury

The Neurobiological Links between Stress and Traumatic Brain Injury: A Review of Research to Date

Neurological dysfunctions commonly occur after mild or moderate traumatic brain injury (TBI). Although most TBI patients recover from such a dysfunction in a short period of time, some present with persistent neurological deficits. Stress is a potential factor that is involved in recovery from neurological dysfunction after TBI. However, there has been limited research on the effects and mechanisms of stress on neurological dysfunctions due to TBI. In this review, we first investigate the effects of TBI and stress on neurological dysfunctions and different brain regions, such as the prefrontal cortex, hippocampus, amygdala, and hypothalamus. We then explore the neurobiological links and mechanisms between stress and TBI. Finally, we summarize the findings related to stress biomarkers and probe the possible diagnostic and therapeutic significance of stress combined with mild or moderate TBI.

The Impact of Preinjury and Secondary Attention-Deficit/Hyperactivity Disorder on Outcomes After Pediatric Traumatic Brain Injury

OBJECTIVE

The objective of this study was to examine the impact of preinjury attention-deficit/hyperactivity disorder (PADHD) and secondary ADHD (SADHD) on outcomes after pediatric traumatic brain injury (TBI).

METHODS

Two hundred eighty-four individuals aged 11 to 18 years hospitalized overnight for a moderate-to-severe TBI were included in this study. Parents completed measures of child behavior and functioning and their own functioning. Linear models examined the effect of ADHD status (PADHD vs SADHD vs no ADHD) on the child's executive functioning (EF), social competence, and functional impairment, and parental depression and distress.

RESULTS

ADHD status had a significant effect on EF [F(2,269] = 9.19, p = 0.0001), social competence (F[2,263] = 32.28, p < 0.0001), functional impairment (F[2,269] = 16.82, p < 0.0001), parental depression (F[2,263] = 5.53, p = 0.005), and parental distress (F[2,259] = 3.57, p = 0.03). PADHD and SADHD groups had greater EF deficits, poorer social competence, and greater functional impairment than the no ADHD group. The SADHD group had greater levels of parental depression than the no ADHD and PADHD groups, and the SADHD group had higher parental distress than the no ADHD group.

CONCLUSION

The results highlight the importance of early identification and management of ADHD symptoms after injury to mitigate downstream functional problems. Supporting parents managing new-onset ADHD symptoms may also be important.

A Systematic Scoping Review of New Attention Problems Following Traumatic Brain Injury in Children

Objective: To summarize existing knowledge about the characteristics of attention problems secondary to traumatic brain injuries (TBI) of all severities in children.

Methods: Computerized databases PubMed and PsychINFO and gray literature sources were used to identify relevant studies. Search terms were selected to identify original research examining new ADHD diagnosis or attention problems after TBI in children. Studies were included if they investigated any severity of TBI, assessed attention or ADHD after brain injury, investigated children as a primary or sub-analysis, and controlled for or excluded participants with preinjury ADHD or attention problems.

Results: Thirty-nine studies were included in the review. Studies examined the prevalence of and risk factors for new attention problems and ADHD following TBI in children as well as behavioral and neuropsychological factors associated with these attention problems. Studies report a wide range of prevalence rates of new ADHD diagnosis or attention problems after TBI. Evidence indicates that more severe injury, injury in early childhood, or preinjury adaptive functioning problems, increases the risk for new ADHD and attention problems after TBI and both sexes appear to be equally vulnerable. Further, literature suggests that cases of new ADHD often co-occurs with neuropsychiatric impairment in other domains. Identified gaps in our understanding of new attention problems and ADHD include if mild TBI, the most common type of injury, increases risk and what brain abnormalities are associated with the emergence of these problems.

Conclusion: This scoping review describes existing studies of new attention problems and ADHD following TBI in children and highlights important risk factors and comorbidities. Important future research directions are identified that will inform the extent of this outcome across TBI severities, its neural basis and points of intervention to minimize its impact.

Three-Month Psychiatric Outcome of Pediatric Mild Traumatic Brain Injury: A Controlled Study

The objective was to clarify occurrence, phenomenology, and risk factors for novel psychiatric disorder (NPD) in the first 3 months after mild traumatic brain injury (mTBI) and orthopedic injury (OI). Children aged 8-15 years with mTBI (n = 220) and with OI but no TBI (n = 110) from consecutive admissions to an emergency department were followed prospectively at baseline and 3 months post-injury with semi-structured psychiatric interviews to document the number of NPDs that developed in each participant. Pre-injury child variables (adaptive, cognitive, and academic function, and psychiatric disorder), pre-injury family variables (socioeconomic status, family psychiatric history, and family function), and injury severity were assessed and analyzed as potential confounders and predictors of NPD. NPD occurred at a significantly higher frequency in children with mTBI versus OI in analyses unadjusted (mean ratio [MR] 3.647, 95% confidence interval [CI₉₅] (1.264, 15.405), p = 0.014) and adjusted (MR = 3.724, CI₉₅ (1.264, 15.945), p = 0.015) for potential confounders. In multi-predictor analyses, the factors besides mTBI that were significantly associated with higher NPD frequency after adjustment for each other were pre-injury lifetime psychiatric disorder [MR = 2.284, CI₉₅ (1.026, 5.305), p = 0.043]; high versus low family psychiatric history [MR = 2.748, CI₉₅ (1.201, 6.839), p = 0.016], and worse socio-economic status [MR = 0.618 per additional unit, CI₉₅ (0.383, 0.973), p = 0.037]. These findings demonstrate that mild injury to the brain compared with an OI had a significantly greater deleterious effect on psychiatric outcome in the first 3 months post-injury. This effect was present even after accounting for specific child and family variables, which were themselves independently related to the adverse psychiatric outcome.

Abnormal Functional Network Topology and Its Dynamics during Sustained Attention Processing Significantly Implicate Post-TBI Attention Deficits in Children

Traumatic brain injury (TBI) is highly prevalent in children. Attention deficits are among the most common and persistent post-TBI cognitive and behavioral sequalae that can contribute to adverse outcomes. This study investigated the topological properties of the functional brain network for sustained attention processing and their dynamics in 42 children with severe post-TBI attention deficits (TBI-A) and 47 matched healthy controls. Functional MRI data during a block-designed sustained attention task was collected for each subject, with each full task block further divided into the pre-, early, late-, and post-stimulation stages. The task-related functional brain network was constructed using the graph theoretic technique. Then, the sliding-window-based method was utilized to assess the dynamics of the topological properties in each stimulation stage. Relative to the controls, the TBI-A group had significantly reduced nodal efficiency and/or degree of left postcentral, inferior parietal, inferior temporal, and fusiform gyri and their decreased stability during the early and late-stimulation stages. The left postcentral inferior parietal network anomalies were found to be significantly associated with elevated inattentive symptoms in children with TBI-A. These results suggest that abnormal functional network characteristics and their dynamics associated with the left parietal lobe may significantly link to the onset of the severe post-TBI attention deficits in children.

Association of Attention-Deficit/Hyperactivity Disorder Diagnoses With Pediatric Traumatic Brain Injury: A Meta-analysis

IMPORTANCE

There are conflicting accounts about the risk for attention-deficit/hyperactivity disorder (ADHD) following traumatic brain injury (TBI), possibly owing to variations between studies in acute TBI severity or when ADHD was assessed postinjury. Analysis of these variations may aid in identifying the risk.

OBJECTIVE

To conduct a meta-analysis of studies assessing ADHD diagnoses in children between ages 4 and 18 years following concussions and mild, moderate, or severe TBI.

DATA SOURCES

PubMed, PsycInfo, and Cochrane Central Register of Controlled Trials (1981-December 19, 2019) were searched including the terms traumatic brain injury, brain injuries, closed head injury, blunt head trauma, concussion, attention deficit disorders, ADHD, and ADD in combination with childhood, adolescence, pediatric, infant, child, young adult, or teen.

STUDY SELECTION

Limited to English-language publications in peer-reviewed journals and patient age (4-18 years). Differences about inclusion were resolved through consensus of 3 authors.

DATA EXTRACTION AND SYNTHESIS

MOOSE guidelines for abstracting and assessing data quality and validity were used. Odds ratios with 95% credible intervals (CrIs) are reported.

MAIN OUTCOMES AND MEASURES

The planned study outcome was rate of ADHD diagnoses.

RESULTS

A total of 12 374 unique patients with TBI of all severity levels and 43 491 unique controls were included in the 24 studies in this review (predominantly male: TBI, 61.8%; noninjury control, 60.9%; other injury control, 66.1%). The rate of pre-TBI ADHD diagnoses was 16.0% (95% CrI, 11.3%-21.7%), which was significantly greater than the 10.8% (95% CrI, 10.2%-11.4%) incidence of ADHD in the general pediatric population. Compared with children without injuries, the odds for ADHD were not significantly increased following concussion (≤1 year: OR, 0.32; 95% CrI, 0.05-1.13), mild TBI (≤1 year: OR, 0.56; 0.16-1.43; >1 year: OR, 1.07; 95% CrI, 0.35-2.48), and moderate TBI (≤1 year: OR, 1.28; 95% CrI, 0.35-3.34; >1 year: OR, 3.67; 95% CrI, 0.83-10.56). The odds for ADHD also were not significantly increased compared with children with other injuries following mild TBI (≤1 year: OR, 1.07; 95% CrI, 0.33-2.47; >1 year: OR, 1.18; 95% CrI, 0.32-3.12) and moderate TBI (≤1 year: OR, 2.34; 95% CrI, 0.78-5.47; >1 year: OR, 3.78; 95% CrI, 0.93-10.33). In contrast, the odds for ADHD following severe TBI were increased at both time points following TBI compared with children with other injuries (≤1 year: OR, 4.81; 95% CrI, 1.66-11.03; >1 year: OR, 6.70; 95% CrI, 2.02-16.82) and noninjured controls (≤1 year: OR, 2.62; 95% CrI, 0.76-6.64; >1 year: OR, 6.25; 95% CrI, 2.06-15.06), as well as those with mild TBI (≤1 year OR, 5.69; 1.46-15.67: >1 year OR, 6.65; 2.14-16.44). Of 5920 children with severe TBI, 35.5% (95% CrI, 20.6%-53.2%) had ADHD more than 1 year postinjury.

CONCLUSIONS AND RELEVANCE

This study noted a significant association between TBI severity and ADHD diagnosis. In children with severe but not mild and moderate TBI, there was an association with an increase in risk for ADHD. The high rate of preinjury ADHD in children with TBI suggests that clinicians should carefully review functioning before a TBI before initiating treatment.

Impact of Secondary ADHD on Long-Term Outcomes After Early Childhood Traumatic Brain Injury

OBJECTIVE

To examine the impact of secondary attention-deficit/hyperactivity disorder (SADHD) on long-term global and executive functioning in adolescents after traumatic brain injury (TBI).

SETTING

Three tertiary cared children's hospitals and 1 general hospital.

PARTICIPANTS

One hundred twenty children (TBI: n = 54; orthopedic injury: n = 66) without preinjury ADHD evaluated approximately 6.8 years postinjury.

DESIGN

Cross-sectional data analysis from a prospective, longitudinal study.

MAIN MEASURES

Outcomes included functional impairment (Child and Adolescent Functional Assessment Scale) and executive functioning (Behavior Rating Inventory of Executive Function [BRIEF]).

RESULTS

SADHD moderated the association of injury type with the BRIEF-Behavioral Regulation Index (F1,113 = 4.42, P = .04) and the Child and Adolescent Functional Assessment Scale (F1,112 = 8.95, P = .003). TBI was only associated with poorer outcomes in the context of SADHD. SADHD was also associated with poorer outcomes on the BRIEF-Global Executive Composite (F1,113 = 52.92, P < .0001) and BRIEF-Metacognitive Index scores (F1,113 = 48.64, P < .0001) across groups. Adolescents with TBI had greater BRIEF-Global Executive Composite scores than those with orthopedic injury (F1,113 = 5.00, P = .03).

CONCLUSIONS

Although SADHD was associated with poorer functioning across groups, its adverse effects on behavioral regulation and overall functioning were amplified following TBI. TBI + SADHD may confer an elevated risk for significant impairments in early adolescence.

Challenges and opportunities for neuroimaging in young patients with traumatic brain injury: a coordinated effort towards advancing discovery from the ENIGMA pediatric moderate/severe TBI group

Traumatic brain injury (TBI) is a major cause of death and disability in children in both developed and developing nations. Children and adolescents suffer from TBI at a higher rate than the general population, and specific developmental issues require a unique context since findings from adult research do not necessarily directly translate to children. Findings in pediatric cohorts tend to lag behind those in adult samples. This may be due, in part, both to the smaller number of investigators engaged in research with this population and may also be related to changes in safety laws and clinical practice that have altered length of hospital stays, treatment, and access to this population. The ENIGMA (Enhancing NeuroImaging Genetics through Meta-Analysis) Pediatric Moderate/Severe TBI (msTBI) group aims to advance research in this area through global collaborative meta-analysis of neuroimaging data. In this paper, we discuss important challenges in pediatric TBI research and opportunities that we believe the ENIGMA Pediatric msTBI group can provide to address them. With the paucity of research studies examining neuroimaging biomarkers in pediatric patients with TBI and the challenges of recruiting large numbers of participants, collaborating to improve statistical power and to address technical challenges like lesions will significantly advance the field. We conclude with recommendations for future research in this field of study.

Frontostriatal White Matter Integrity Relations with "Cool" and "Hot" Self-Regulation after Pediatric Traumatic Brain Injury

Traumatic brain injury (TBI) produces microstructural damage to white matter pathways connecting neural structures in pre-frontal and striatal regions involved in self-regulation (SR). Dorsal and ventral frontostriatal pathways have been linked to cognitive ("cool") and emotional ("hot") SR, respectively. We evaluated the relation of frontostriatal pathway fractional anisotropy (FA) 2 months post-TBI on cool and hot SR assessed 7 months post-TBI. Participants were 8-15 years of age, including children with uncomplicated mild TBI (mTBI; n = 24), more severe TBI (complicated-mild, moderate, severe [cms]TBI; n = 60), and typically developing (TD) children (n = 55). Diffusion tensor tractography was used to map frontostriatal pathways. Cool SR included focused and sustained attention performance, and parent-reported attention, whereas hot SR included risk-taking performance and parent-reported emotional control. Multivariate general linear models showed that children with cmsTBI had greater parent-reported cool and hot SR difficulties and lower dorsal and ventral FA than TD children. Focused attention, risk taking, and emotional control correlated with FA of specific dorsal and ventral pathways; however, only the effect of TBI on focused attention was mediated by integrity of dorsal pathways. Results suggest that frontostriatal FA may serve as a biomarker of risk for SR difficulties or to assess response to interventions targeting SR in pediatric TBI and in broader neurodevelopmental populations.

ADHD: Current Concepts and Treatments in Children and Adolescents

Attention deficit hyperactivity disorder (ADHD) is among the most frequent disorders within child and adolescent psychiatry, with a prevalence of over 5%. Nosological systems, such as the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) and the International Classification of Diseases, editions 10 and 11 (ICD-10/11) continue to define ADHD according to behavioral criteria, based on observation and on informant reports. Despite an overwhelming body of research on ADHD over the last 10 to 20 years, valid neurobiological markers or other objective criteria that may lead to unequivocal diagnostic classification are still lacking. On the contrary, the concept of ADHD seems to have become broader and more heterogeneous. Thus, the diagnosis and treatment of ADHD are still challenging for clinicians, necessitating increased reliance on their expertise and experience. The first part of this review presents an overview of the current definitions of the disorder (DSM-5, ICD-10/11). Furthermore, it discusses more controversial aspects of the construct of ADHD, including the dimensional versus categorical approach, alternative ADHD constructs, and aspects pertaining to epidemiology and prevalence. The second part focuses on comorbidities, on the difficulty of distinguishing between "primary" and "secondary" ADHD for purposes of differential diagnosis, and on clinical diagnostic procedures. In the third and most prominent part, an overview of current neurobiological concepts of ADHD is given, including neuropsychological and neurophysiological researches and summaries of current neuroimaging and genetic studies. Finally, treatment options are reviewed, including a discussion of multimodal, pharmacological, and nonpharmacological interventions and their evidence base.

Influence of Methylphenidate on Long-Term Neuropsychological and Everyday Executive Functioning After Traumatic Brain Injury in Children with Secondary Attention Problems

OBJECTIVE

To investigate the effects of methylphenidate on long-term executive and neuropsychological functioning in children with attention problems following TBI, as well as the relationship between methylphenidate associated changes in lab-based neuropsychological measures of attentional control, processing speed, and executive functioning and parent- or self-report measures of everyday executive functioning.

METHOD

26 children aged 6-17 years, who were hospitalized for moderate-to-severe blunt head trauma 6 or more months previously, were recruited from a large children's hospital medical center. Participants were randomized into a double-masked, placebo-controlled cross-over clinical trial. Participants completed a comprehensive neuropsychological battery and parent- and self-report ratings of everyday executive functioning at baseline, and at 4 weeks and 8 weeks following upward titration of medication to an optimal dose or while administered a placebo.

RESULTS

Methylphenidate was associated with significant improvements in processing speed, sustained attention, and both lab-based and everyday executive functioning. Significant treatment-by-period interactions were found on a task of sustained attention. Participants who were randomized to the methylphenidate condition for the first treatment period demonstrated random or erratic responding, with slower and more variable response times when given placebo during the second period.

CONCLUSION

Results indicate that methylphenidate treatment is associated with positive outcomes in processing speed, sustained attention, and both lab-based and everyday measures of executive functioning compared to placebo group. Additionally, results suggest sustained attention worsens when discontinuing medication. (JINS, 2019, 25, 740-749).

Traumatic brain injury: a potential cause of violent crime?

Traumatic brain injury (TBI) is the biggest cause of death and disability in children and young people. TBI compromises important neurological functions for self-regulation and social behaviour and increases risk of behavioural disorder and psychiatric morbidity. Crime in young people is a major social issue. So-called early starters often continue for a lifetime. A substantial majority of young offenders are reconvicted soon after release. Multiple factors play a role in crime. We show how TBI is a risk factor for earlier, more violent, offending. TBI is linked to poor engagement in treatment, in-custody infractions, and reconviction. Schemes to assess and manage TBI are under development. These might improve engagement of offenders in forensic psychotherapeutic rehabilitation and reduce crime.

Traumatic Brain Injury, Sleep Disorders, and Psychiatric Disorders: An Underrecognized Relationship

Traumatic brain injury (TBI) is commonplace among pediatric patients and has a complex, but intimate relationship with psychiatric disease and disordered sleep. Understanding the factors that influence the risk for the development of TBI in pediatrics is a critical component of beginning to address the consequences of TBI. Features that may increase risk for experiencing TBI sometimes overlap with factors that influence the development of post-concussive syndrome (PCS) and recovery course. Post-concussive syndrome includes physical, psychological, cognitive and sleep-wake dysfunction. The comorbid presence of sleep-wake dysfunction and psychiatric symptoms can lead to a more protracted recovery and deleterious outcomes. Therefore, a multidisciplinary evaluation following TBI is necessary. Treatment is generally symptom specific and mainly based on adult studies. Further research is necessary to enhance diagnostic and therapeutic approaches, as well as improve the understanding of contributing pathophysiology for the shared development of psychiatric disease and sleep-wake dysfunction following TBI.

Psychiatric Sequelae of Concussions

PURPOSE OF REVIEW

The purpose of this study was to review the frequency, risk factors, phenomenology, and course of prolonged recovery from concussion and of psychiatric sequelae in pediatric populations.

RECENT FINDINGS

Youth with prolonged recovery from concussions have higher initial symptoms, a history of multiple and/or recent concussions, and a tendency to somatization. Depression, post-traumatic stress disorder, behavioral disorders, and perhaps, suicidal behavior disorder are more common as both short- and longer-term sequelae of concussions. The weight of evidence supports a graduated return to function as compared to prolonged rest, which may actually impede recovery. For those with prolonged recovery, cognitive behavior therapy aimed at education about concussions, improving coping, problem-solving, sleep hygiene, and dealing with anxiety and depression provided in a collaborative care model is superior to usual care. Concussed youth have an increased risk of psychiatric symptoms and sleep disturbance that can be prevented or treated with proper management.

Pediatric Traumatic Brain Injury and Autism: Elucidating Shared Mechanisms

Pediatric traumatic brain injury (TBI) and autism spectrum disorder (ASD) are two serious conditions that affect youth. Recent data, both preclinical and clinical, show that pediatric TBI and ASD share not only similar symptoms but also some of the same biologic mechanisms that cause these symptoms. Prominent symptoms for both disorders include gastrointestinal problems, learning difficulties, seizures, and sensory processing disruption. In this review, we highlight some of these shared mechanisms in order to discuss potential treatment options that might be applied for each condition. We discuss potential therapeutic and pharmacologic options as well as potential novel drug targets. Furthermore, we highlight advances in understanding of brain circuitry that is being propelled by improved imaging modalities. Going forward, advanced imaging will help in diagnosis and treatment planning strategies for pediatric patients. Lessons from each field can be applied to design better and more rigorous trials that can be used to improve guidelines for pediatric patients suffering from TBI or ASD.

The effect of premorbid attention-deficit/hyperactivity disorder on neuropsychological functioning in individuals with acute mild traumatic brain injuries

INTRODUCTION

Mild traumatic brain injury (mTBI) is a frequent, yet undertreated condition that typically manifests with transient neurological and cognitive symptoms that resolve over the course of several weeks. In contrast, attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that presents initially in childhood but often persists into adulthood. mTBI and ADHD include overlapping symptomatology, making it difficult for clinicians to disentangle the sequelae of each condition when they co-occur in the same individual. We hypothesized that neuropsychological tests would be sensitive to preexisting ADHD in inpatients with acute mTBIs.

METHOD

We retrospectively examined the medical charts of 100 inpatients, aged 18-40 years (96% Caucasian; 77% male) with mTBIs in an acute care setting, half of whom had self-reported the presence of premorbid ADHD, and half of whom were matched controls. We analyzed group differences across neuropsychological tests of attention, processing speed, and executive functions, examined the profile ratings of independent, blinded, board-certified neuropsychologists, and correlated cognitive performance with time from traumatic injury to testing.

RESULTS

Individuals with premorbid ADHD (a) performed significantly worse than their matched counterparts on several tests of attention, processing speed, and working memory, and (b) were significantly more likely to produce profiles later rated as impaired by independent, board-certified clinical neuropsychologists. In addition, time from traumatic injury to testing was found to be negatively correlated with neurocognitive performance.

CONCLUSIONS

These findings (a) argue for the utility of a brief assessment of premorbid ADHD in the acute care of individuals with mTBIs and (b) provide clinicians with a barometer for gauging the relative contributions of premorbid ADHD to neuropsychological impairments in the neurocognitive profiles of individuals with mTBIs. Reported effect sizes will assist clinicians in accurately weighing the impact of premorbid ADHD when interpreting such profiles.

Successful treatment of an adult with symptomatic attention deficit, hyperactivity, and impulsivity after temporal lobe resection: case report

Attention deficit hyperactivity disorder (ADHD) is defined by inattentiveness, impulsivity, and/or hyperactivity and mandatorily requires an onset in childhood. Structural or functional anatomical abnormalities have mostly been found in the prefrontal cortex, the corpus callosum, the striatum, and the cerebellum. We here present the case of an adult woman who developed severe symptoms analogous to ADHD after right temporal lobectomy. Surgery had been necessary because of a large temporobasal arterio-venous malformation (AVM). The patient's childhood and personal history before surgery had been without any indication of ADHD or any other mental disorder. Because of her distinct and impairing symptoms of ADHD, we initiated off-label methylphenidate treatment, achieving strong reduction in the symptoms. This proves further similarity of her symptomatic disorder to ADHD and supports a role of the right temporal lobe in ADHD.

Personality Change Due to Traumatic Brain Injury in Children and Adolescents: Neurocognitive Correlates

Personality change due to traumatic brain injury (PC) in children is an important psychiatric complication of injury and is a form of severe affective dysregulation. This study aimed to examine neurocognitive correlates of PC. The sample included 177 children 5-14 years old with traumatic brain injury who were enrolled from consecutive admissions to five trauma centers. Patients were followed up prospectively at baseline and at 6 months, and they were assessed with semistructured psychiatric interviews. Injury severity, socioeconomic status, and neurocognitive function (measures of attention, processing speed, verbal memory, IQ, verbal working memory, executive function, naming/reading, expressive language, motor speed, and motor inhibition) were assessed with standardized instruments. Unremitted PC was present in 26 (18%) of 141 participants assessed at 6 months postinjury. Attention, processing speed, verbal memory, IQ, and executive function were significantly associated with PC even after socioeconomic status, injury severity, and preinjury attention deficit hyperactivity disorder were controlled. These findings are a first step in characterizing concomitant cognitive impairments associated with PC. The results have implications beyond brain injury to potentially elucidate the neurocognitive symptom complex associated with mood instability regardless of etiology.