Biomedical subjects

Susan L Smalley

Publications and source records attributed to Susan L Smalley.

12 recordsLinked to original sources

PubMed2006

Familial association and frequency of learning disabilities in ADHD sibling pair families.

In a sample of 235 families with at least two children with Attention-Deficit/ Hyperactivity Disorder (ADHD), the frequency and familial association of learning disabilities (LD) were assessed. Familiality was examined both between sibling pairs and between parents and their children. Two methods for defining LD, a discrepancy-based and a low-achievement model, were employed to examine the occurrence of LD in this sample. The specific types of LD examined included Reading Disability (RD), Math Disability (MD), and Writing Disability (WD). The prevalence rates were highest for RD, followed by WD then MD. The two definitions of LD yielded similar prevalence rates but identified different groups of children with vastly different IQ scores. Strong familial association was demonstrated for RD both between sibling pairs and between parents and children, with weaker association for WD. There was evidence of nonrandom mating for LD among parents, but not for ADHD or for ADHD + LD. Despite the high comorbidity of ADHD and LD among parents, the presence of ADHD in the parents did not predict child LD supporting independent familial factors underlying ADHD and LD.

Adolescent↗

PubMed2006

Relationship of family environment and parental psychiatric diagnosis to impairment in ADHD.

OBJECTIVE: Family environmental factors as well as parental attention-deficit/hyperactivity disorder (ADHD) status have shown associations with variability in ADHD. The purpose of the present study was to examine the links among family environment, parental psychiatric diagnosis, and child impairment within a sample of ADHD-affected sibling pairs (ASPs) ages 5 to 18 years. METHOD: Parents in 220 ASP families completed a measure of family functioning, the Family Environment Scale. Children's impairment was measured by clinical ratings of global functioning and by maternal ratings of behavior. RESULTS: Parents of children with ADHD rate their families as higher in conflict and lower in achievement and organization than normative samples. High family conflict is significantly associated with impairment in ADHD ASPs accounting for approximately 40% of the sibling similarity in impairment. Parental psychiatric diagnosis revealed no significant direct link to sibling impairment, but rather a significant indirect link to impairment mediated by family conflict. Direct associations with parental diagnosis depend on birth order of the ASP members despite the comparable mean impairment scores for older and younger ADHD siblings. CONCLUSIONS: There are strong links between impairment in children with ADHD and family environment. Different processes and mechanisms may contribute to impairment in different children in the same family.

Adolescent↗

PubMed2005

Toward localizing genes underlying cerebral asymmetry and mental health.

Genome investigations of autism, attention deficit hyperactivity disorder (ADHD), and dyslexia suggest possible genetic overlap. Atypical cerebral asymmetry (ACA), the absence of the left hemisphere dominance for language, may be a shared phenotype due to genes located in regions of overlap. A binomal test is used to evaluate whether linked regions overlap more than expected by chance for 15 genome-wide scans in autism, ADHD, and dyslexia. Significant evidence of linkage overlap (P = 10(-7)) is seen for autism, ADHD, and dyslexia for seven chromosomal regions (2p11-12, 5p13, 7q22-33, 9q33-34, 13q22, 16p13, and 17p11-q11). Linkage analysis of ACA and molecular markers for 270 sibling pairs with ADHD is conducted using the Haseman-Elston statistic. Linkage analysis supports ACA as a shared phenotype with risk genes located on 9q33-34 or 16p13 (P < 0.004). Further support stems from the overlap of these regions in schizophrenia, bipolar illness, specific language impairment (SLI), and handedness, all traits associated with ACA. Autism, ADHD, and dyslexia share regions of linkage overlap and ACA may be a shared phenotype for such genes similar to HLA in autoimmune disease. Because ACA is associated with certain aspects of creativity, such risk genes may also be enhancer genes for creativity.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Collaborative analysis of DRD4 and DAT genotypes in population-defined ADHD subtypes.

BACKGROUND: It has been proposed that some of the variability in reporting of associations between attention deficit hyperactivity disorder (ADHD) and candidate genes may result from mixing of genetically heterogeneous forms of ADHD using DSM-IV criteria. The goal of the current study is to test whether population-based ADHD subtypes defined by latent class analysis help resolve issues of variable findings across individual gene association studies. METHODS: Three studies which had previously reported no associations between polymorphisms of the DRD4 and DAT genes and DSM-IV defined ADHD were reanalyzed using population-based and DSM-IV defined ADHD subtypes. RESULTS: Across studies no significant associations were found for either DRD4 or DAT polymorphisms using DSM-IV ADHD subtypes. In contrast, a significant association was found between the combined data set for the 440 base pair 3' DAT VNTR polymorphism and population-defined severe combined ADHD (OR=1.25, p=.01). A marginally significant association was also found between the 7 repeat DRD4 allele and population-defined severe combined ADHD. CONCLUSION: Use of alternative population-based defined ADHD subtypes may help resolve some of the variable results presented for candidate gene association studies in ADHD.

Adolescent↗

PubMed2005

Temperament and character profiles and the dopamine D4 receptor gene in ADHD.

OBJECTIVE: This study was designed to investigate the link among attention deficit hyperactivity disorder (ADHD) in adults, novelty-seeking temperament, and the 48-base pair (bp) dopamine D4 receptor (DRD4) gene variant. METHOD: This study drew from a larger molecular genetic study of ADHD in which the ascertainment criterion was having an affected sibling pair with ADHD. Parents (N=171) from 96 families provided data. Of the 171 parents, 56 (33%) had a lifetime history of ADHD, with 28 (50%) continuing to meet DSM-IV criteria (i.e., "persistent" ADHD). Latent variable modeling was used to test whether the DRD4 gene variant or Temperament and Character Inventory factors could predict ADHD. RESULTS: Using latent variable modeling, the authors were able to confirm the first-order factor structure of the Temperament and Character Inventory. Furthermore, novelty seeking predicted ADHD lifetime diagnosis (R(2)=26%), while the DRD4 gene variant independently predicted ADHD (R(2)=5%) but not novelty seeking. CONCLUSIONS: In this unique sample of parents from multiply affected ADHD families, novelty seeking and the 48-bp DRD4 variant were associated with a lifetime history of ADHD. However, the association between novelty seeking and ADHD does not appear to be due to variation in the 48-bp DRD4 variant.

Adult↗

PubMed2005

Psychiatric comorbidity in adult attention deficit hyperactivity disorder: findings from multiplex families.

OBJECTIVE: Patterns of psychiatric comorbidity were assessed in adults with and without attention deficit hyperactivity disorder (ADHD) identified through a genetic study of families containing multiple children with ADHD. METHOD: Lifetime ADHD and comorbid psychopathology were assessed in 435 parents of children with ADHD. Rates and mean ages at onset of comorbid psychopathology were compared in parents with lifetime ADHD, parents with persistent ADHD, and those without ADHD. Age-adjusted rates of comorbidity were compared with Kaplan-Meier survival curves. Logistic regression was used to assess additional risk factors for conditions more frequent in ADHD subjects. RESULTS: The parents with ADHD were significantly more likely to be unskilled workers and less likely to have a college degree. ADHD subjects had more lifetime psychopathology; 87% had at least one and 56% had at least two other psychiatric disorders, compared with 64% and 27%, respectively, in non-ADHD subjects. ADHD was associated with greater disruptive behavior, substance use, and mood and anxiety disorders and with earlier onset of major depression, dysthymia, oppositional defiant disorder, and conduct disorder. Group differences based on Kaplan-Meier age-corrected risks were consistent with those for raw frequency distributions. Male sex added risk for disruptive behavior disorders. Female sex and oppositional defiant disorder contributed to risk for depression and anxiety. ADHD was not a significant risk factor for substance use disorders when male sex, disruptive behavior disorders, and socioeconomic status were controlled. CONCLUSIONS: Adult ADHD is associated with significant lifetime psychiatric comorbidity that is not explained by clinical referral bias.

Adolescent↗

PubMed2004

Attention deficit hyperactivity disorder: fine mapping supports linkage to 5p13, 6q12, 16p13, and 17p11.

We completed fine mapping of nine positional candidate regions for attention-deficit/hyperactivity disorder (ADHD) in an extended population sample of 308 affected sibling pairs (ASPs), constituting the largest linkage sample of families with ADHD published to date. The candidate chromosomal regions were selected from all three published genomewide scans for ADHD, and fine mapping was done to comprehensively validate these positional candidate regions in our sample. Multipoint maximum LOD score (MLS) analysis yielded significant evidence of linkage on 6q12 (MLS 3.30; empiric P=.024) and 17p11 (MLS 3.63; empiric P=.015), as well as suggestive evidence on 5p13 (MLS 2.55; empiric P=.091). In conjunction with the previously reported significant linkage on the basis of fine mapping 16p13 in the same sample as this report, the analyses presented here indicate that four chromosomal regions--5p13, 6q12, 16p13, and 17p11--are likely to harbor susceptibility genes for ADHD. The refinement of linkage within each of these regions lays the foundation for subsequent investigations using association methods to detect risk genes of moderate effect size.

Attention Deficit Disorder with Hyperactivity↗

PubMed2004

Joint analysis of the DRD5 marker concludes association with attention-deficit/hyperactivity disorder confined to the predominantly inattentive and combined subtypes.

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable, heterogeneous disorder of early onset, consisting of a triad of symptoms: inattention, hyperactivity, and impulsivity. The disorder has a significant genetic component, and theories of etiology include abnormalities in the dopaminergic system, with DRD4, DAT1, SNAP25, and DRD5 being implicated as major susceptibility genes. An initial report of association between ADHD and the common 148-bp allele of a microsatellite marker located 18.5 kb from the DRD5 gene has been followed by several studies showing nonsignificant trends toward association with the same allele. To establish the postulated association of the (CA)(n) repeat with ADHD, we collected genotypic information from 14 independent samples of probands and their parents, analyzed them individually and, in the absence of heterogeneity, analyzed them as a joint sample. The joint analysis showed association with the DRD5 locus (P=.00005; odds ratio 1.24; 95% confidence interval 1.12-1.38). This association appears to be confined to the predominantly inattentive and combined clinical subtypes.

Attention Deficit Disorder with Hyperactivity↗

PubMed2003

A genomewide scan for attention-deficit/hyperactivity disorder in an extended sample: suggestive linkage on 17p11.

Attention-deficit/hyperactivity disorder (ADHD [MIM 143465]) is a common, highly heritable neurobehavioral disorder of childhood onset, characterized by hyperactivity, impulsivity, and/or inattention. As part of an ongoing study of the genetic etiology of ADHD, we have performed a genomewide linkage scan in 204 nuclear families comprising 853 individuals and 270 affected sibling pairs (ASPs). Previously, we reported genomewide linkage analysis of a "first wave" of these families composed of 126 ASPs. A follow-up investigation of one region on 16p yielded significant linkage in an extended sample. The current study extends the original sample of 126 ASPs to 270 ASPs and provides linkage analyses of the entire sample, using polymorphic microsatellite markers that define an approximately 10-cM map across the genome. Maximum LOD score (MLS) analysis identified suggestive linkage for 17p11 (MLS=2.98) and four nominal regions with MLS values >1.0, including 5p13, 6q14, 11q25, and 20q13. These data, taken together with the fine mapping on 16p13, suggest two regions as highly likely to harbor risk genes for ADHD: 16p13 and 17p11. Interestingly, both regions, as well as 5p13, have been highlighted in genomewide scans for autism.

Adolescent↗

PubMed2003

Maternal smoking and hyperactivity in 8-year-old children.

OBJECTIVE: To investigate the association between maternal smoking during pregnancy and hyperactivity in 8-year-old children. METHOD: The study population consisted of children from the Northern Finland 1985/86 Birth Cohort. At 8-year follow-up 9,357 children were alive. Mothers provided information both during pregnancy and at age 8. Teachers assessed children's behavior by the Children's Behavior Questionnaire (Rutter B2). Unadjusted analyses and stratification were used to study associations and confounding variables. A multivariate logistic regression model was fitted to assess the independent association between smoking and outcome. RESULTS: Maternal smoking was associated with hyperactivity even after adjustment for sex, family structure, socioeconomic status, maternal age, and maternal alcohol use (odds ratio 1.30; 1.08-1.58). The association was particularly notable among children of young mothers with low social standing. A positive dose-response relationship was seen between maternal smoking and hyperactivity. CONCLUSION: This study, the largest population-based prospective follow-up on fetal nicotine exposure and later behavioral disorders, confirms earlier descriptions of the link between maternal smoking during gestation and childhood hyperactivity. Discontinuation or decreased use of cigarettes during pregnancy might improve behavioral outcome of children.

Adult↗

PubMed2002

Genetic linkage of attention-deficit/hyperactivity disorder on chromosome 16p13, in a region implicated in autism.

Attention-deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed behavioral disorder in childhood and likely represents an extreme of normal behavior. ADHD significantly impacts learning in school-age children and leads to impaired functioning throughout the life span. There is strong evidence for a genetic etiology of the disorder, although putative alleles, principally in dopamine-related pathways suggested by candidate-gene studies, have very small effect sizes. We use affected-sib-pair analysis in 203 families to localize the first major susceptibility locus for ADHD to a 12-cM region on chromosome 16p13 (maximum LOD score 4.2; P=.000005), building upon an earlier genomewide scan of this disorder. The region overlaps that highlighted in three genome scans for autism, a disorder in which inattention and hyperactivity are common, and physically maps to a 7-Mb region on 16p13. These findings suggest that variations in a gene on 16p13 may contribute to common deficits found in both ADHD and autism.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

A genomewide scan for loci involved in attention-deficit/hyperactivity disorder.

Attention deficit/hyperactivity disorder (ADHD) is a common heritable disorder with a childhood onset. Molecular genetic studies of ADHD have previously focused on examining the roles of specific candidate genes, primarily those involved in dopaminergic pathways. We have performed the first systematic genomewide linkage scan for loci influencing ADHD in 126 affected sib pairs, using a approximately 10-cM grid of microsatellite markers. Allele-sharing linkage methods enabled us to exclude any loci with a lambda(s) of > or =3 from 96% of the genome and those with a lambda(s) of > or =2.5 from 91%, indicating that there is unlikely to be a major gene involved in ADHD susceptibility in our sample. Under a strict diagnostic scheme we could exclude all screened regions of the X chromosome for a locus-specific lambda(s) of >/=2 in brother-brother pairs, demonstrating that the excess of affected males with ADHD is probably not attributable to a major X-linked effect. Qualitative trait maximum LOD score analyses pointed to a number of chromosomal sites that may contain genetic risk factors of moderate effect. None exceeded genomewide significance thresholds, but LOD scores were >1.5 for regions on 5p12, 10q26, 12q23, and 16p13. Quantitative-trait analysis of ADHD symptom counts implicated a region on 12p13 (maximum LOD 2.6) that also yielded a LOD >1 when qualitative methods were used. A survey of regions containing 36 genes that have been proposed as candidates for ADHD indicated that 29 of these genes, including DRD4 and DAT1, could be excluded for a lambda(s) of 2. Only three of the candidates-DRD5, 5HTT, and CALCYON-coincided with sites of positive linkage identified by our screen. Two of the regions highlighted in the present study, 2q24 and 16p13, coincided with the top linkage peaks reported by a recent genome-scan study of autistic sib pairs.

Alleles↗