• CAG-Repeat length in exon 1 of KCNN3 does not influence risk for schizophrenia or bipolar disorder: A meta-analysis of association studies

      Glatt, Stephen J.; Faraone, Stephen V.; Tsuang, Ming T. (Wiley, 2003-07-30)
      Schizophrenia and bipolar disorder both showsomeevidence for genetic anticipation. In addition, significant expansion of anonymous CAG repeats throughout the genome has been detected in both of these disorders. The gene KCNN3, which codes for a small/ intermediate conductance, calcium-regulated potassium channel, contains a highly polymorphic CAG-repeat array in exon 1. Initial evidence for association of both schizophrenia and bipolar disorder with increased CAG-repeat length of KCNN3 has not been consistently replicated. In the present study, we performed several metaanalyses to evaluate the pooled evidence for association with CAG-repeat length of KCNN3 derived from case-control and family-based studies of both disorders. Each group of studies was analyzed under two models, including a test for direct association with repeat length, and a test for association with dichotomized repeat-length groups. No evidence for a linear relationship between disease risk and repeat length was observed, as all pooled odds ratios approximated 1.0. Results of dichotomized allelegroup analyses were more variable, especially for schizophrenia, where case-control studies found a significant association with longer repeats but family-based studies implicated shorter alleles. The results of these meta-analyses demonstrate that the risks for both schizophrenia and bipolar disorder are largely, if not entirely, independent of CAG-repeat length in exon 1 of KCNN3. This study cannot exclude the possibility that some aspect of this polymorphism, such as repeat-length disparity in heterozygotes, influences risk for these disorders. Further, it remains unknown if this polymorphism, or one in linkage disequilibrium with it, contributes to some distinct feature of the disorder, such as symptom severity or anticipation.
    • Can sodium/hydrogen exchange inhibitors be repositioned for treating attention deficit hyperactivity disorder? An in silico approach

      Faraone, Stephen V.; Zhang-James, Yanli (Wiley, 2013-10-17)
      Medications for attention deficit hyperactivity disorder (ADHD) are only partially effective. Ideally, new treatment targets would derive from a known pathophysiology. Such data are not available for ADHD. We combine evidence for new etiologic pathways with bioinformatics data to assess the possibility that existing drugs might be repositioning for treating ADHD. We use this approach to determine if prior data implicating the sodium/hydrogen exchanger 9 gene (SLC9A9) in ADHD implicate sodium/hydrogen exchange (NHE) inhibitors as potential treatments. We assessed the potential for repositioning by assessing the similarity of drug–protein binding profiles between NHE inhibitors and drugs known to treat ADHD using the Drug Repositioning and Adverse Reaction via Chemical–Protein Interactome server. NHE9 shows a high degree of amino acid similarity between NHE inhibitor sensitive NHEs in the region of the NHE inhibitor recognition site defined for NHE1. We found high correlations in drug–protein binding profiles among most ADHD drugs. The drug–protein binding profiles of some NHE inhibitors were highly correlated with ADHD drugs whereas the profiles for a control set of nonsteroidal anti-inflammatory drugs (NSAIDs) were not. Further experimental work should evaluate if NHE inhibitors are suitable for treating ADHD. © 2013 Wiley Periodicals, Inc.
    • Characteristics of Adults with Attention Deficit Hyperactivity Disorder Plus Substance Use Disorder: The Role of Psychiatric Comorbidity

      Wilens, Timothy E.; Kwon, Anne; Tanguay, Sarah; Chase, Rhea; Moore, Hadley; Faraone, Stephen V.; Biederman, Joseph (Wiley, 2005-01)
      The objective of the study was to investigate the characteristics of adults with Attention Deficit Hyperactivity Disorder (ADHD) or substance use disorder (SUD), especially in the context of comorbid psychiatric disorders. Subjects were adults (n ¼ 78) participating in a controlled family study of ADHD and SUD. Four groups were identified based on a diagnosis of ADHD or SUD: ADHD, SUD, ADHDþSUD, and neither ADHD nor SUD. All diagnoses were determined by structured clinical interview for DSM IV. Rates of psychiatric comorbidity were lowest in the controls, intermediate in the ADHD and SUD groups, and highest in the ADHDþSUD group. Relative to controls, the ADHD, SUD, and ADHDþSUD groups had higher rates of major depression (z ¼ 1.98, p ¼ 0.05), conduct disorder (z ¼ 2.0, p ¼ 0.04), antisocial personality disorder (z ¼ 2.6, p ¼ 0.009), agoraphobia (z ¼ 2.5, p ¼ 0.01) and social phobia (z ¼ 2.7, p ¼ 0.007). Higher rates of psychiatric comorbidity, especially mood and anxiety disorders, exist in subjects with SUDþADHD relative to subjects with SUD, ADHD, or controls. Clinicians need to be attentive to other psychiatric disorders that may occur in the large group of adults with ADHDþSUD.
    • Comorbidity of ADHD and adult bipolar disorder: A systematic review and meta-analysis

      Schiweck, Carmen; Arteaga-Henriquez, Gara; Aichholzer, Mareike; Edwin Thanarajah, Sharmili; Vargas-Cáceres, Sebastian; Matura, Silke; Grimm, Oliver; Haavik, Jan; Kittel-Schneider, Sarah; Ramos-Quiroga, Josep Antoni; et al. (Elsevier BV, 2021-05)
      Attention-deficit / hyperactivity disorder (ADHD) and Bipolar Disorder (BD) are common mental disorders with a high degree of comorbidity. However, no systematic review with meta-analysis has aimed to quantify the degree of comorbidity between both disorders. To this end we performed a systematic search of the literature in October 2020. In a meta-analysis of 71 studies with 646,766 participants from 18 countries, it was found that about one in thirteen adults with ADHD was also diagnosed with BD (7.95 %; 95 % CI: 5.31-11.06), and nearly one in six adults with BD had ADHD (17.11 %; 95 % CI: 13.05-21.59 %). Substantial heterogeneity of comorbidity rates was present, highlighting the importance of contextual factors: Heterogeneity could partially be explained by diagnostic system, sample size and geographical location. Age of BD onset occurred earlier in patients with comorbid ADHD (3.96 years; 95 % CI: 2.65-5.26, p < 0.001). Cultural and methodological differences deserve attention for evaluating diagnostic criteria and clinicians should be aware of the high comorbidity rates to prevent misdiagnosis and provide optimal care for both disorders.
    • The concept of target features in schizophrenia research

      Tsuang, M. T.; Faraone, S. V. (Wiley, 1999-05)
      Target features are clinical or neurobiological characteristics that arc expressions of the underlying predisposition to an illness. They comprise a wide range of phenomena, from thc classic signs and symptoms of psychopathology to sophisticated measures of brain structure and function. For schizophrenia, many target features have been identified. These include eye tracking dysfunction, attentional impairment, allusive thinking, neurological signs, thought disorder, characteristic auditory evoked potentials, neuropsychological impairment, structural brain abnormalities and functional brain abnormalities. In their most pathological forms, thcse features are present among many schizophrenic patients, yet it is their presence among their non-psychotic relatives that shows them to be target features. We discuss the theoretical background for target features, present examples and describe how the discovery of target features has implications I for schizophrenia research.
    • Consortium neuroscience of attention deficit/hyperactivity disorder and autism spectrum disorder: The ENIGMA adventure

      Hoogman, Martine; Rooij, Daan; Klein, Marieke; Boedhoe, Premika; Ilioska, Iva; Li, Ting; Patel, Yash; Postema, Merel C.; Zhang‐James, Yanli; Anagnostou, Evdokia; et al. (Wiley, 2020-05-18)
      Neuroimaging has been extensively used to study brain structure and function in individuals with attention deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) over the past decades. Two of the main shortcomings of the neuroimaging literature of these disorders are the small sample sizes employed and the heterogeneity of methods used. In 2013 and 2014, the ENIGMA-ADHD and ENIGMA-ASD working groups were respectively, founded with a common goal to address these limitations. Here, we provide a narrative review of the thus far completed and still ongoing projects of these working groups. Due to an implicitly hierarchical psychiatric diagnostic classification system, the fields of ADHD and ASD have developed largely in isolation, despite the considerable overlap in the occurrence of the disorders. The collaboration between the ENIGMA-ADHD and -ASD working groups seeks to bring the neuroimaging efforts of the two disorders closer together. The outcomes of case–control studies of subcortical and cortical structures showed that subcortical volumes are similarly affected in ASD and ADHD, albeit with small effect sizes. Cortical analyses identified unique differences in each disorder, but also considerable overlap between the two, specifically in cortical thickness. Ongoing work is examining alternative research questions, such as brain laterality, prediction of case–control status, and anatomical heterogeneity. In brief, great strides have been made toward fulfilling the aims of the ENIGMA collaborations, while new ideas and follow-up analyses continue that include more imaging modalities (diffusion MRI and resting-state functional MRI), collaborations with other large databases, and samples with dual diagnoses.
    • A Controlled Study of Behavioral Inhibition in Children of Parents With Panic Disorder and Depression

      Rosenbaum, Jerrold F.; Biederman, Joseph; Hirshfeld-Becker, Dina R.; Kagan, Jerome; Snidman, Nancy; Friedman, Deborah; Nineberg, Allan; Gallery, Daniel J.; Faraone, Stephen V. (American Psychiatric Association Publishing, 2000-12)
      Objective: “Behavioral inhibition to the unfamiliar” has been proposed as a precursor to anxiety disorders. Children with behavioral inhibition are cautious, quiet, introverted, and shy in unfamiliar situations. Several lines of evidence suggest that behavioral inhibition is an index of anxiety proneness. The authors sought to replicate prior findings and examine the specificity of the association between behavioral inhibition and anxiety. Method: Laboratory-based behavioral observations were used to assess behavioral inhibition in 129 young children of parents with panic disorder and major depression, 22 children of parents with panic disorder without major depression, 49 children of parents with major depression without panic disorder, and 84 children of parents without anxiety disorders or major depression (comparison group). A standard definition of behavioral inhibition based on previous research (“dichotomous behavioral inhibition”) was compared with two other definitions. Results: Dichotomous behavioral inhibition was most frequent among the children of parents with panic disorder plus major depression (29% versus 12% in comparison subjects). For all definitions, the univariate effects of parental major depression were significant (conferring a twofold risk for behavioral inhibition), and for most definitions the effects of parental panic disorder conferred a twofold risk as well. Conclusions: These results suggest that the comorbidity of panic disorder and major depression accounts for much of the observed familial link between parental panic disorder and childhood behavioral inhibition. Further work is needed to elucidate the role of parental major depression in conferring risk for behavioral inhibition in children.
    • Deficient Emotional Self-Regulation and Adult Attention Deficit Hyperactivity Disorder: A Family Risk Analysis

      Surman, Craig B.H.; Biederman, Joseph; Spencer, Thomas; Yorks, Dayna; Miller, Carolyn A.; Petty, Carter R.; Faraone, Stephen V. (American Psychiatric Association Publishing, 2011-06)
      Objective: A growing body of research suggests that deficient emotional self-regulation (DESR) is prevalent and morbid among patients with attention deficit hyperactivity disorder (ADHD). Family studies provide a method of clarifying the co-occurrence of clinical features, but no family studies have yet addressed ADHD and DESR. Method: Participants were 83 probands with and without ADHD and 128 siblings. All were assessed for axis I DSM-IV conditions with structured diagnostic interviews. The authors defined DESR in adult probands and siblings using items from the Barkley Current Behavior Scale. Analyses tested hypotheses about the familial relationship between ADHD and DESR. Results: Siblings of ADHD probands were at elevated risk of having ADHD, irrespective of the presence or absence of DESR in the proband. The risk for DESR was elevated in siblings of ADHD plus DESR probands but not in siblings of ADHD probands. ADHD and DESR cosegregated in siblings. The risk for other psychiatric disorders was similar in siblings of the ADHD proband groups. Conclusions: The pattern of inheritance of ADHD with DESR preliminarily suggests that DESR may be a familial subtype of ADHD. Our data suggest that DESR is not an expression of other axis I DSM-IV disorders or of nonfamilial environmental factors. The authors cannot exclude contribution of non-axis-I DSM-IV disorders to risk for DESR and cannot determine whether the cosegregation of ADHD in DESR within families is a result of genes or familial environmental risk factors. Further investigation of DESR and its correlates and treatment both in and outside the context of ADHD is warranted.
    • Deletion at the SLC1A1 glutamate transporter gene co-segregates with schizophrenia and bipolar schizoaffective disorder in a 5-generation family

      Myles-Worsley, Marina; Tiobech, Josepha; Browning, Sharon R.; Korn, Jeremy; Goodman, Sarah; Gentile, Karen; Melhem, Nadine; Byerley, William; Faraone, Stephen V.; Middleton, Frank A. (Wiley, 2013-01-22)
      Growing evidence for genetic overlap between schizophrenia (SCZ) and bipolar disorder (BPD) suggests that causal variants of large effect on disease risk may cross traditional diagnostic boundaries. Extended multigenerational families with both SCZ and BPD cases can be a valuable resource for discovery of shared biological pathways because they can reveal the natural evolution of the underlying genetic disruptions and their phenotypic expression. We investigated a deletion at the SLC1A1 glutamate transporter gene originally identified as a copy number variant exclusively carried by members of a 5-generation Palauan family. Using an expanded sample of 21 family members, quantitative PCR confirmed the deletion in all seven individuals with psychosis, three “obligate-carrier” parents and one unaffected sibling, while four marry-in parents were non-carriers. Linkage analysis under an autosomal dominant model generated a LOD-score of 3.64, confirming co-segregation of the deletion with psychosis. For more precise localization, we determined the approximate deletion end points using alignment of next-generation sequencing data for one affected deletion-carrier and then designed PCR amplicons to span the entire deletion locus. These probes established that the deletion spans 84,298 bp, thus eliminating the entire promoter, the transcription start site, and the first 59 amino acids of the protein, including the first transmembrane Na2+/dicarboxylate symporter domain, one of the domains that perform the glutamate transport action. Discovery of this functionally relevant SLC1A1 mutation and its co-segregation with psychosis in an extended multigenerational pedigree provides further support for the important role played by glutamatergic transmission in the pathophysiology of psychotic disorders. © 2013 Wiley Periodicals, Inc.
    • Differential Effect of Environmental Adversity by Gender: Rutter’s Index of Adversity in a Group of Boys and Girls With and Without ADHD

      Biederman, Joseph; Faraone, Stephen V.; Monuteaux, Michael C. (American Psychiatric Association Publishing, 2002-09)
      Objective: This study examined the effect of gender in mediating the association between environmental adversity and the risk of attention deficit hyperactivity disorder (ADHD) and associated impairments. Method: The authors studied 280 ADHD and 242 healthy comparison probands of both genders who were between the ages of 6 and 17 years. They tested the association between Rutter’s indicators of adversity (including family conflict, social class, family size, maternal psychopathology, and paternal criminality) and ADHD, comorbidity, and functioning. Results: Greater levels of environmental adversity were associated with a greater risk for ADHD and other comorbidity in both genders in a dose-dependent fashion. However, learning disability and global functioning were modified by gender, with more detrimental effects observed in boys than in girls. Low social class, maternal psychopathology, and family conflict were significantly associated with psychopathology and functional impairment in the probands, with control for gender, parental ADHD, proband ADHD status, and maternal smoking during pregnancy. Conclusions: Psychosocial adversity in general and low social class, maternal psychopathology, and family conflict in particular increased the risk for ADHD and associated morbidity independently of gender and other risk factors, but gender modified the risk for adverse cognitive and interpersonal outcomes; boys were more vulnerable to the disorder than girls. Because of the difficulties in separating the effects of genetics from environment, these results must be interpreted as provisional until confirmation from twin and adoption studies.
    • Disorder Versus Disability: The Challenge of ADHD in the Context of a High IQ

      Antshel, Kevin M.; Hendricks, Kaitlin; Faraone, Stephen V.; Gordon, Michael (Guilford Publications, 2011-04)
    • Dopamine D4 Gene 7-Repeat Allele and Attention Deficit Hyperactivity Disorder

      Faraone, Stephen V.; Biederman, Joseph; Weiffenbach, Barbara; Keith, Tim; Chu, Monica P.; Weaver, Alix; Spencer, Thomas J.; Wilens, Timothy E.; Frazier, Jean; Cleves, Mario; et al. (American Journal of Psychiatry, 1999-05)
      Objective: Family, twin, and adoption studies show attention deficit hyperactivity disorder (ADHD) to have a substantial genetic component, and some studies have reported an association between ADHD and the dopamine D4 (DRD4) gene. Method: The authors recruited 27 triads that comprised an ADHD adult, his or her spouse, and their ADHD child. These triads were assessed for ADHD, and their DNA was genotyped for DRD4 alleles. Results: A multiallelic transmission disequilibrium test suggested an association between ADHD and the DRD4 7-repeat allele. Among family members, the number of 7-repeat alleles predicted the diagnosis of ADHD. Conclusions: Prior reports of an association between ADHD and DRD4 generalize to families recruited through clinically referred ADHD adults. However, because there are some conflicting studies, further work is needed to clarify the role of DRD4 in the etiology of the disorder.
    • The dopamine receptor D4 7-repeat allele influences neurocognitive functioning, but this effect is moderated by age and ADHD status: An exploratory study

      Altink, Marieke E.; Rommelse, Nanda N.J.; Slaats-Willemse, Dorine I.E.; Väsquez, Alejandro Arias; Franke, Barbara; Buschgens, Cathelijne J.M.; Fliers, Ellen A.; Faraone, Stephen V.; Sergeant, Joseph A.; Oosterlaan, Jaap; et al. (Informa UK Limited, 2011-11-23)
      Objectives. Evidence suggests the involvement of the dopamine D4 receptor gene ( DRD4 ) in the pathogenesis of ADHD, but the exact mechanism is not well understood. Earlier reports on the effects of DRD4 polymorphisms on neurocognitive and neuroimaging measures are inconsistent. This study investigated the functional consequences of the 7-repeat allele of DRD4 on neurocognitive endophenotypes of ADHD in the Dutch subsample of the International Multicenter ADHD Genetics study. Methods. Participants were 350 children (5 – 11.5 years) and adolescents (11.6 – 19 years) with ADHD and their 195 non-affected siblings. An overall measure of neuropsychological functioning was derived by principal component analysis from five neurocognitive and five motor tasks. The effects of DRD4 and age were examined using Linear Mixed Model analyses. Results. The analyses were stratified for affected and non-affected participants after finding a significant three-way interaction between ADHD status, age and the 7-repeat allele. Apart from a main effect of age, a significant interaction effect of age and DRD4 was found in non-affected but not in affected participants, with non-affected adolescent carriers of the 7-repeat allele showing worse neuropsychological performance. In addition, carrying the 7-repeat allele of DRD4 was related to a significantly worse performance on verbal working memory in non-affected siblings, independent of age. Conclusions. These results might indicate that the effect of the DRD4 7-repeat allele on neuropsychological functioning is dependent on age and ADHD status.
    • Dr. Glatt and Colleagues Reply

      Glatt, Stephen J.; FARAONE, STEPHEN V.; Tsuang, Ming T. (American Psychiatric Association Publishing, 2004-06)
    • DRAMS: A tool to detect and re-align mixed-up samples for integrative studies of multi-omics data

      Jiang, Yi; Giase, Gina; Grennan, Kay; Shieh, Annie W.; Xia, Yan; Han, Lide; Wang, Quan; Wei, Qiang; Chen, Rui; Liu, Sihan; et al. (Public Library of Science (PLoS), 2020-04-13)
    • Effectiveness and Tolerability of Tomoxetine in Adults With Attention Deficit Hyperactivity Disorder

      Spencer, Thomas; Biederman, Joseph; Wilens, Timothy; Prince, Jeffry; Hatch, Mary; Jones, Janice; Harding, Margaret; Faraone, Stephen V.; Seidman, Larry (American Psychiatric Association Publishing, 1998-05)
      Objective: The authors assessed the experimental noradrenergic compound tomoxetine as an alternative treatment for adult attention deficit hyperactivity disorder (ADHD). Method: They conducted a double-blind, placebo-controlled, crossover study of tomoxetine in 22 adults with well-characterized ADHD. Results: Treatment with tomoxetine at an average oral dose of 76 mg/day was well tolerated. Drug-specific improvement in ADHD symptoms was highly significant overall and sufficiently robust to be detectable in a parallel-groups comparison restricted to the first 3 weeks of the protocol. Eleven of 21 patients showed improvement after receiving tomoxetine, compared with only two of 21 patients who improved after receiving placebo. Significant tomoxetine-associated improvement was noted on neuropsychological measures of inhibitory capacity from Stroop tests. Conclusions: This preliminary study showed that tomoxetine was effective in treating adult ADHD and was well tolerated. These promising results provide support for further studies of tomoxetine over an extended period of treatment.
    • Environmental risk factors for attention‐deficit hyperactivity disorder

      Banerjee, Tania Das; Middleton, Frank; Faraone, Stephen V. (Wiley, 2007-06-15)
      Attention-deficit hyperactivity disorder (ADHD) is the most common cognitive and behavioural disorder diagnosed among school children. It is characterized by deficient attention and problem solving, along with hyperactivity and difficulty withholding incorrect responses. This highly prevalent disorder is estimated to affect 5–10% of children and in many cases, persists into adulthood, leading to 4% prevalence among adults. Converging evidence from epidemiologic, neuropsychology, neuroimaging, genetic and treatment studies shows that ADHD is a valid medical disorder. The majority of studies performed to assess genetic risk factors in ADHD have supported a strong familial nature of this disorder. Family studies have identified a 2- to 8-fold increase in the risk for ADHD in parents and siblings of children with ADHD. Various twin and adoption studies have also highlighted the highly genetic nature of ADHD. In fact the mean heritability of ADHD was shown to be 0.77, which is comparable to other neuropsychiatric disorders such as schizophrenia or bipolar disorder. However, several biological and environmental factors have also been proposed as risk factors for ADHD, including food additives/diet, lead contamination, cigarette and alcohol exposure, maternal smoking during pregnancy, and low birth weight. Many recent studies have specifically examined the relationships between ADHD and these extraneous factors. This review describes some of these possible risk factors.
    • Evidence for Similar Structural Brain Anomalies in Youth and Adult Attention-Deficit/Hyperactivity Disorder: A Machine Learning Analysis

      Zhang-James, Yanli; Helminen, Emily C; Liu, Jinru; Franke, Barbara; Hoogman, Martine; Faraone, Stephen V (Cold Spring Harbor Laboratory, 2019-02-11)
      Attention-deficit/hyperactivity disorder (ADHD) affects 5% of children world-wide. Of these, two-thirds continue to have impairing symptoms of ADHD into adulthood. Although a large literature implicates structural brain differences of the disorder, it is not clear if adults with ADHD have similar neuroanatomical differences as those seen in children with recent reports from the large ENIGMA-ADHD consortium finding structural differences for children but not for adults. This paper uses deep learning neural network classification models to determine if there are neuroanatomical changes in the brains of children with ADHD that are also observed for adult ADHD, and vice versa. We found that structural MRI data can significantly separate ADHD from control participants for both children and adults. Consistent with the prior reports from ENIGMA-ADHD, prediction performance and effect sizes were better for the child than the adult samples. The model trained on adult samples significantly predicted ADHD in the child sample, suggesting that our model learned anatomical features that are common to ADHD in childhood and adulthood. These results support the continuity of ADHD’s brain differences from childhood to adulthood. In addition, our work demonstrates a novel use of neural network classification models to test hypotheses about developmental continuity.
    • Evidence for the multigenic inheritance of schizophrenia

      Freedman, Robert; Leonard, Sherry; Olincy, Ann; Kaufmann, Charles A.; Malaspina, Dolores; Cloninger, C. Robert; Svrakic, Dragan; Faraone, Stephen V.; Tsuang, Ming T. (Wiley, 2002-08-21)
      Schizophrenia is assumed to have complex inheritance because of its high prevalence and sporadic familial transmission. Findings of linkage on different chromosomes in various studies corroborate this assumption. It is not known whether these ®endings represent heterogeneous inheritance, in which various ethnic groups inherit illness through different major gene effects, or multigenic inheritance, in which affected individuals inherit several common genetic abnormalities. This study therefore examined inheritance of schizophrenia at different genetic loci in a nationally collected European American and African American sample. Seventy-seven families were previously genotyped at 458 markers for the NIMH Schizophrenia Genetics Initiative. Initial genetic analysis tested a dominant model, with schizophrenia and schizoaffective disorder, depressed type, as the affected phenotype. The families showed one genome-wide significant linkage (Z ¼ 3.97) at chromosome 15q14, which maps within 1 cM of a previous linkage at the a7-nicotinic receptor gene. Chromosome 10p13 showed suggestive linkage (Z ¼ 2.40). Six others (6q21, 9q32, 13q32, 15q24, 17p12, 20q13) were positive, with few differences between the two ethnic groups. The probability of each family transmitting schizophrenia through two genes is greater than expected from the combination of the independent segregation of each gene. Two trait-locus linkage analysis supports a model in which genetic alleles associated with schizophrenia are relatively common in the general population and affected individuals inherit risk for illness through at least two different loci.
    • Examining the Comorbidity Between Attention Deficit Hyperactivity Disorder and Bipolar I Disorder: A Meta-Analysis of Family Genetic Studies

      Faraone, Stephen V.; Biederman, Joseph; Wozniak, Janet (American Psychiatric Association Publishing, 2012-12)
      Objective: The existence of comorbidity between attention deficit hyperactivity disorder (ADHD) and bipolar I disorder has been documented in clinical and epidemiological studies, in studies of children and adults, and in diagnosed ADHD and bipolar I patient samples. Yet questions remain about the validity of diagnosing bipolar I disorder in ADHD youth. The authors aim to clarify these issues by reviewing family genetic studies of ADHD and bipolar I disorder. Method: The authors applied randomeffects meta-analysis to family genetic studies of ADHD and bipolar I disorder. Twenty bipolar proband studies provided 37 estimates of the prevalence of ADHD in 4,301 relatives of bipolar probands and 1,937 relatives of comparison probands. Seven ADHD proband studies provided 12 estimates of the prevalence of bipolar I disorder in 1,877 relatives of ADHD probands and 1,601 relatives of comparison probands. Results: These studies found a significantly higher prevalence of ADHD among relatives of bipolar probands and a significantly higher prevalence of bipolar I disorder among relatives of ADHD probands. These results could not be accounted for by publication biases, unusual results from any one observation, sample characteristics, or study design features. The authors found no evidence of heterogeneity in the ADHD or bipolar family studies. Conclusions: The results suggest that ADHD plus bipolar comorbidity cannot be accounted for by misdiagnoses, but additional research is needed to rule out artifactual sources of comorbidity. More research is also needed to determine whether comorbidity of ADHD and bipolar I disorder constitutes a familial subtype distinct from its constituent disorders, which if confirmed would have implications for diagnostic nosology and genetic studies.