Aaron J Bobb

National Institute of Mental Health (NIMH), Bethesda, MD, United States

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Publications (7)48.03 Total impact

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    ABSTRACT: Clozapine is a unique atypical antipsychotic with superior efficacy in treatment-resistant schizophrenia. Plasma concentration of clozapine and its major metabolite N-desmethylclozapine (NDMC) as well as the ratio of NDMC to clozapine have been reported to be predictors of clozapine response. Here we evaluate these as well as other measures in an effort to find predictors of response to clozapine in our early-onset treatment-refractory population. Fifty-four children and adolescents participated in double-blind (n = 22) or open-label (n = 32) clozapine trials. Clinical evaluations took place at baseline, week 6 on clozapine, and at 2- to 6-year follow-up. The data were analyzed in relation to demographics, age at onset, IQ, clozapine dose, and plasma concentrations of prolactin, clozapine, NDMC, and NDMC/clozapine ratio. Stepwise regression and correlation analyses were performed to find predictors of treatment response. Clinical improvement after 6 weeks of clozapine treatment, as measured by the percentage of improvement on the Brief Psychiatric Rating Scale and the Scale for the Assessment of Positive Symptoms, was strongly associated with the NDMC/clozapine ratio at the 6-week time point (Pearson correlation coefficient: r = 0.41; p < .01 for Brief Psychiatric Rating Scale and r = 0.43; p < .01 for Scale for the Assessment of Positive Symptoms). Although the rate of side effects was higher than that typically found in the adult population, it did not appear to be related to clozapine dose, clozapine or NDMC plasma concentrations, or NDMC/clozapine ratio. Outcome at long-term follow-up, as measured by Children's Global Assessment Scale, was associated with lesser illness severity at baseline and with greater improvement during the initial 6 weeks of clozapine treatment. The NDMC/clozapine ratio may be a valuable predictor of response to clozapine and may suggest new approaches to clozapine treatment.
    Journal of the American Academy of Child & Adolescent Psychiatry 10/2007; 46(10):1349-56. · 6.97 Impact Factor
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    ABSTRACT: Polymorphisms of the dopamine receptor D4 gene DRD4, 11p15.5, have previously been associated with attention-deficit/hyperactivity disorder (ADHD) [Bobb et al., 2005; Am J Med Genet B Neuropsychiatr Genet 132:109-125; Faraone et al., 2005; Biol Psychiatry 57:1313-1323; Thapar et al., 2005; Hum Mol Genet 14 Spec No. 2:R275-R282]. As a follow up to a pilot study [see Castellanos et al., 1998; Mol Psychiatry 3:431-434] consisting of 41 probands and 56 controls which found no significant association between the DRD4 7-repeat allele in exon 3 and ADHD, a greatly expanded study sample (cases n = 166 and controls n = 282) and long term follow-up (n = 107, baseline mean age n = 9, follow-up mean age of n = 15) prompted reexamination of this gene. The DRD4 7-repeat allele was significantly more frequent in ADHD cases than controls (OR = 1.2; P = 0.028). Further, within the ADHD group, the 7-repeat allele was associated with better cognitive performance (measured by the WISC-III) (P = 0.013-0.07) as well as a trend for association with better long-term outcome. This provides further evidence of the role of the DRD4 7-repeat allele in the etiology of ADHD and suggests that this allele may be associated with a more benign form of the disorder.
    American Journal of Medical Genetics Part B Neuropsychiatric Genetics 05/2007; 144B(3):379-82. · 3.23 Impact Factor
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    ABSTRACT: 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. 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. 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. 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.
    Journal of the American Academy of Child & Adolescent Psychiatry 10/2005; 44(9):925-33. · 6.97 Impact Factor
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    ABSTRACT: Pre-, peri-, and postnatal obstetric complications (OC) are reported to be more frequent in adult patients with schizophrenia and have been linked to both greater severity and to "earlier" age of onset (before either age 18 or 22) in studies of adult patients. We hypothesized that by extrapolation, patients with childhood-onset schizophrenia (COS), with very early onset and very severe illness, would have had more numerous or more salient OC compared with their healthy siblings. We compared the obstetric records of 60 COS children and 48 healthy siblings using the Columbia Obstetrics Complication Scale, a comprehensive measurement scale consisting of 37 variables having included a separate scale for fetal hypoxia. Patients with COS did not have a higher incidence of OC than the healthy sibling control group with the exception of increased incidence of maternal vomiting. Obstetric complications, with the possible exception of maternal vomiting, are unlikely to play a major role in the etiopathogenesis of childhood-onset schizophrenia.
    Biological Psychiatry 08/2005; 58(1):10-5. · 9.25 Impact Factor
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    ABSTRACT: Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia.
    Molecular Psychiatry 07/2005; 10(6):581-8. · 15.15 Impact Factor
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    ABSTRACT: 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.
    American Journal of Medical Genetics Part B Neuropsychiatric Genetics 04/2005; 134B(1):67-72. · 3.23 Impact Factor
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    ABSTRACT: Attention deficit hyperactivity disorder (ADHD)is highly heritable but is likely a complex disorder involving multiple genes of moderate effect (Smalley [1997: Am J Hum Genet 60:1276-12821]). Over 100 studies have examined the genetics of ADHD by linkage or association, though no article has presented a comprehensive overview of all published reports. We reviewed all ADHD studies, including 3 genome-wide linkage studies, and association studies of 94 polymorphisms in 33 candidate genes. To simplify comparisons across heterogeneous articles, demographics and comorbidity were ignored; analyses of subtype and haplotypes were excluded; and only the most positive finding for each polymorphism in a study was reported. Thirty-six percent of all findings were positive (P< 0.05), 17% were trends (0.05 <P < 0.15), and 47% were negative (P > 0.15). Studies utilizing dimensional measures of ADHD tended to result in higher rates of positive findings than those using categorical diagnoses (X(2) = 5.6, P = 0.018), and case-control studies tended to result in higher rates of positive findings than family-based studies (X(2) = 18.8, P < 0.001). However, for either dichotomy, no significant difference remained when analyzing only studies using both methods within the same population and polymorphism. Evidence for association exists for four genes in ADHD: the dopamine D4 and D5 receptors, and the dopamine and serotonin transporters; others are promising but need further replication, including the dopamine D2 and serotonin 2A receptors. All candidate gene approaches continue to face the problem of relatively low power, given modest odds ratios for even the best replicated genes.
    American Journal of Medical Genetics Part B Neuropsychiatric Genetics 01/2005; 132B(1):109-25. · 3.23 Impact Factor