Cerebellar development and clinical outcome in attention deficit hyperactivity disorder.

OBJECTIVE: Anatomic magnetic resonance imaging (MRI) studies have detected smaller cerebellar volumes in children with attention deficit hyperactivity disorder (ADHD) than in comparison subjects. However, the regional specificity and longitudinal progression of these differences remain to be determined. The authors compared the volumes of each lobe of the cerebellar hemispheres and vermis in children with ADHD and comparison subjects and used a new regional cerebellar volume measurement to characterize the developmental trajectory of these differences. METHOD: In a longitudinal case-control study, 36 children with ADHD were divided into a group of 18 with better outcomes and a group of 18 with worse outcomes and were compared with 36 matched healthy comparison subjects. The volumes of six cerebellar hemispheric lobes, the central white matter, and three vermal subdivisions were determined from MR images acquired at baseline and two or more follow-up scans conducted at 2-year intervals. A measure of global clinical outcome and DSM-IV criteria were used to define clinical outcome. RESULTS: In the ADHD groups, a nonprogressive loss of volume was observed in the superior cerebellar vermis; the volume loss persisted regardless of clinical outcome. ADHD subjects with a worse clinical outcome exhibited a downward trajectory in volumes of the right and left inferior-posterior cerebellar lobes, which became progressively smaller during adolescence relative to both comparison subjects and ADHD subjects with a better outcome. CONCLUSIONS: Decreased volume of the superior cerebellar vermis appears to represent an important substrate of the fixed, nonprogressive anatomical changes that underlie ADHD. The cerebellar hemispheres constitute a more plastic, state-specific marker that may prove to be a target for clinical intervention.

Neurologic examination abnormalities in children with bipolar disorder or attention-deficit/hyperactivity disorder.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BPD) are frequently comorbid and overlapping diagnoses. To move beyond diagnosis toward unique pathophysiology, we evaluated both ADHD and BPD children for neurologic examination abnormalities (NEAs) in comparison with normal control (NC) children. METHODS: We performed the Revised Physical and Neurological Examination for Soft Signs in three groups (ADHD, BPD, NC). Then, a rater blind to diagnosis evaluated their motor performance. Results were analyzed with a multiple analysis of covariance. RESULTS: Subjects with ADHD were impaired on repetitive task reaction time. In contrast, pediatric BPD subjects, both with and without comorbid ADHD, were impaired on sequential task reaction time. CONCLUSIONS: This differential pattern of NEAs by diagnosis suggests pathophysiologic differences between ADHD and BPD in children. Repetitive motor performance requires inhibition of nonrelevant movements; ADHD subjects' impairment in this domain supports the hypothesis that ADHD involves a core deficit of fronto-striato-basal ganglia neurocircuitry. In contrast, BPD subjects' impaired sequential motor performance is consistent with behavioral data showing impaired attentional set-shifting and reversal learning in BPD subjects. Further study, going beyond symptom description to determine pathophysiologic differences, is required to refine neuronal models of these often comorbid diagnoses.

Hormonal correlates of clozapine-induced weight gain in psychotic children: an exploratory study.

OBJECTIVE: Weight gain is a serious side effect of atypical antipsychotics, especially in childhood. In this study, the authors examined six weight gain-related hormones in patients with childhood-onset schizophrenia (COS) after 6 weeks of clozapine treatment. METHOD: Fasting serum samples for 24 patients with COS and 21 matched healthy controls (HC) were obtained. Levels of leptin, insulin, adiponectin, amylin, ghrelin, and tumor necrosis factor alpha were measured and compared between the groups. For 23 patients with COS, hormonal levels were measured at background and week 6 of clozapine treatment. Change in body mass index was correlated with levels of clozapine and changes in hormonal levels and clinical ratings. RESULTS: At baseline, COS did not differ significantly from HC on any hormonal measure. Clozapine treatment was associated with significant (7.9% +/- 8.5%) increase in mean body mass index. Only leptin levels increased significantly from baseline to week 6 on clozapine (p = .003). Body mass index increase was significantly correlated with decrease in ghrelin and adiponectin and was positively correlated with clinical improvement. CONCLUSIONS: This is the first study of weight gain-related hormones in children on clozapine. Hormonal changes are correlated with weight gain. How effectiveness of clozapine is linked to weight gain remains uncertain.

Pervasive developmental disorder and childhood-onset schizophrenia: comorbid disorder or a phenotypic variant of a very early onset illness?

BACKGROUND: Childhood-onset schizophrenia (COS) is a severe form of the adult-onset disorder with a high rate of premorbid developmental abnormalities. Early symptoms of pervasive developmental disorder (PDD) have been reported in five independent studies of COS. In this study, we compared evidence for premorbid PDD as a nonspecific manifestation of impaired neurodevelopment seen in schizophrenia, or as an independent risk factor for COS. METHODS: Diagnosis of past or current autism or PDD was made according to the DSM-IV criteria. COS patients with and without PDD were compared with respect to neuropsychological, clinical, and neurobiological measures. Several candidate genes for autism were examined in the entire COS sample and the subgroup with PDD using the Transmission Disequilibrium Test (TDT) and Quantitative TDT (QTDT). RESULTS: Nineteen (25%) of COS probands had a lifetime diagnosis of PDD: one met criteria for autism, two for Asperger's disorder, and 16 for PDD not otherwise specified. Premorbid social impairment was most common feature for COS-PDD subjects. The PDD group did not differ from the rest of the COS sample with respect to age of onset, IQ, response to medications, and rate of familial schizotypy. Unexpectedly, two siblings of COS-PDD probands met criteria for nuclear autism. There was no difference between PDD and non-PDD groups with respect to initial brain magnetic resonance imaging (MRI) measures. However, rate of gray matter loss was greater for PDD (n = 12) than for the non-PDD (n = 27) subgroup (-19.5 +/- 11.3 mL/year vs. -9.6 +/- 15.3 mL/year; p =.05). None of eight candidate genes for autism were associated with COS or COS-PDD. CONCLUSIONS: Premorbid PDD in COS is more likely to be a nonspecific marker of severe early abnormal neurodevelopment. However, the occurrence of two siblings of COS-PDD probands (17%) with nuclear autism remains to be understood.

Anatomic brain abnormalities in monozygotic twins discordant for attention deficit hyperactivity disorder.

OBJECTIVE: To examine brain-behavior relationships in attention deficit hyperactivity disorder (ADHD), the authors obtained magnetic resonance imaging (MRI) scans of monozygotic twins discordant for ADHD. METHOD: National recruitment was followed by in-person assessment. MRI scans were measured algorithmically for nine pairs of monozygotic twins discordant for ADHD. RESULTS: The affected twins had significantly smaller caudate volumes (mean difference=-0.56 ml, CI=-0.92 to -0.21) than their unaffected co-twins. CONCLUSIONS: These results provide further support for striatal models of ADHD pathophysiology.

Monozygotic twins discordant for attention-deficit/hyperactivity disorder: ascertainment and clinical characteristics.

OBJECTIVE: Nongenetic factors and phenomenology of attention-deficit/hyperactivity disorder (ADHD) were examined in monozygotic (MZ) twin pairs discordant for ADHD. METHOD: Recruitment included telephone screening (n = 297 pairs), behavioral ratings obtained from parents and teachers (n = 59 pairs), and, finally, in-person assessment (n = 25 pairs; structured classroom observation, diagnostic interview, psychoeducational evaluation, birth record review, establishment of monozygosity, and anatomic brain imaging). Affected twins were further contrasted with previously studied affected singletons. RESULTS: Of the 25 MZ twin pairs qualifying for in-person evaluation, only 10 proved discordant for ADHD. Affected twins were mostly comparable with affected singletons on clinical measures, although fathers' self-ratings of childhood ADHD status were significantly lower in twins than in singletons. CONCLUSIONS: Discordance for ADHD in MZ twins appears to be ascribable to greater environmental discordance and decreased familiality. Despite these differences, affected twins were phenotypically comparable with affected singletons. Thus MZ twins discordant for ADHD, while rare, can inform research on the etiology and pathophysiology of this disorder.

Cytogenetic abnormalities in attention-deficit/hyperactivity disorder.

OBJECTIVE: To systematically assess the prevalence of fragile X syndrome, velocardiofacial syndrome, and other cytogenetic abnormalities in a group of children with attention-defict/hyperactivity disorder (ADHD). METHOD: Blood samples were obtained from 100 children (64 boys) with combined type ADHD and normal intelligence and analyzed for the presence of fragile X mutation expansions, the 22q11.2 microdeletion associated with velocardiofacial syndrome, and cytogenetic abnormalities that would be detected with high resolution chromosomal banding. RESULTS: One girl with ADHD had a sex chromosome aneuploidy (47,XXX). One boy had a premutation-sized allele for fragile X; no subjects showed the full mutation. Testing for 22q11.2 microdeletion was negative for all subjects with ADHD screened. None of these differences exceeded those expected by chance. CONCLUSIONS: In the absence of clinical signs or positive family history, these relatively expensive laboratory assessments are not clinically indicated for children with ADHD and normal intelligence, and are not recommended as a component of other genetic investigations of this disorder.

Psychostimulant treatment and the developing cortex in attention deficit hyperactivity disorder.

OBJECTIVE: While there has been considerable concern over possible adverse effects of psychostimulants on brain development, this issue has not been examined in a prospective study. The authors sought to determine prospectively whether psychostimulant treatment for attention deficit hyperactivity disorder (ADHD) was associated with differences in the development of the cerebral cortex during adolescence. METHOD: Change in cortical thickness was estimated from two neuroanatomic MRI scans in 43 youths with ADHD. The mean age at the first scan was 12.5 years, and at the second scan, 16.4 years. Nineteen patients not treated with psychostimulants between the scans were compared with an age-matched group of 24 patients who were treated with psychostimulants. Further comparison was made against a template derived from 620 scans of 294 typically developing youths without ADHD. RESULTS: Adolescents taking psychostimulants differed from those not taking psychostimulants in the rate of change of the cortical thickness in the right motor strip, the left middle/inferior frontal gyrus, and the right parieto-occipital region. The group difference was due to more rapid cortical thinning in the group not taking psychostimulants (mean cortical thinning of 0.16 mm/year [SD=0.17], compared with 0.03 mm/year [SD=0.11] in the group taking psychostimulants). Comparison against the typically developing cohort without ADHD showed that cortical thinning in the group not taking psychostimulants was in excess of age-appropriate rates. The treatment groups did not differ in clinical outcome, however. CONCLUSIONS: These findings show no evidence that psychostimulants were associated with slowing of overall growth of the cortical mantle.

Support for association between ADHD and two candidate genes: NET1 and DRD1.

Attention deficit hyperactivity disorder (ADHD) is a common, multifactorial disorder with significant genetic contribution. Multiple candidate genes have been studied in ADHD, including the norepinephrine transporter (NET1) and dopamine D1 receptor (DRD1). NET1 is implicated in ADHD because of the efficacy of atomoxetine, a selective noradrenergic reuptake inhibitor, in the treatment of ADHD. DRD1 is primarily implicated through mouse models of ADHD. DNA from 163 ADHD probands, 192 parents, and 129 healthy controls was used to investigate possible associations between ADHD and polymorphisms in 12 previously studied candidate genes (5-HT1B, 5-HT2A, 5-HT2C, ADRA2A, CHRNA4, COMT, DAT1, DRD1, DRD4, DRD5, NET1, and SNAP-25). Analyses included case-control and family-based methods, and dimensional measures of behavior, cognition, and anatomic brain magnetic resonance imaging (MRI). Of the 12 genes examined, two showed a significant association with ADHD. Transmission disequilibrium test (TDT) analysis revealed significant association of two NET1 single nucleotide polymorphisms (SNPs) with ADHD (P < or = 0.009); case-control analysis revealed significant association of two DRD1 SNPs with ADHD (P < or = 0.008). No behavioral, cognitive, or brain MRI volume measurement significantly differed across NET1 or DRD1 genotypes at an alpha of 0.01. This study provides support for an association between ADHD and polymorphisms in both NET1 and DRD1; polymorphisms in ten other candidate genes were not associated with ADHD. Because family-based and case-control methods gave divergent results, both should be used in genetic studies of ADHD.