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The adult form of attention-deficit/hyperactivity disorder has a prevalence of up to 5% and is the most severe long-term outcome of this common disorder. Family studies in clinical samples as well as twin studies suggest a familial liability and consequently different genes were investigated in association studies. Pharmacotherapy with methylphenidate (MPH) seems to be the first-line treatment of choice in adults with attention-deficit hyperactive disorder (ADHD) and some studies were conducted on the genes influencing the response to this drug. Finally some peripheral biomarkers were identified in ADHD adult patients. We believe this work is the first systematic review and meta-analysis of candidate gene association studies, pharmacogenetic and biochemical (metabolomics) studies performed in adults with ADHD to identify potential genetic, predictive and peripheral markers linked specifically to ADHD in adults. After screening 5129 records, we selected 87 studies of which 61 were available for candidate gene association studies, 5 for pharmacogenetics and 21 for biochemical studies. Of these, 15 genetic, 2 pharmacogenetic and 6 biochemical studies were included in the meta-analyses. We obtained an association between adult ADHD and the gene BAIAP2 (brain-specific angiogenesis inhibitor 1-associated protein 2), even after Bonferroni correction, with any heterogeneity in effect size and no publication bias. If we did not apply the Bonferroni correction, a trend was found for the carriers allele 9R of dopamine transporter SLC6A3 40 bp variable tandem repeat polymorphism (VNTR) and for 6/6 homozygotes of SLC6A3 30 bp VNTR. Negative results were obtained for the 9-6 haplotype, the dopamine receptor DRD4 48 bp VNTR, and the enzyme COMT SNP rs4680. Concerning pharmacogenetic studies, no association was found for the SLC6A3 40 bp and response to MPH with only two studies selected. For the metabolomics studies, no differences between ADHD adults and controls were found for salivary cortisol, whereas lower serum docosahexaenoic acid (DHA) levels were found in ADHD adults. This last association was significant even after Bonferroni correction and in absence of heterogeneity. Other polyunsaturated fatty acids (PUFAs) such as AA (arachidonic acid), EPA (eicosapentaenoic acid) and DyLA (dihomogammalinolenic acid) levels were not different between patients and controls. No publication biases were observed for these markers. Genes linked to dopaminergic, serotoninergic and noradrenergic signaling, metabolism ( DBH, TPH1, TPH2, DDC, MAOA, MAOB, BCHE and TH ), neurodevelopment ( BDNF and others), the SNARE system and other forty genes/proteins related to different pathways were not meta-analyzed due to insufficient data. In conclusion, we found that there were not enough genetic, pharmacogenetic and biochemical studies of ADHD in adults and that more investigations are needed. Moreover we confirmed a significant role of BAIAP2 and DHA in the etiology of ADHD exclusively in adults. Future research should be focused on the replication of these findings and to assess their specificity for ADHD.

The adult form of attention deficit/hyperactivity disorder (aADHD) has a prevalence of up to 5% and is the most severe long-term outcome of this common neurodevelopmental disorder. Family studies in clinical samples suggest an increased familial liability for aADHD compared with childhood ADHD (cADHD), whereas twin studies based on self-rated symptoms in adult population samples show moderate heritability estimates of 30–40%. However, using multiple sources of information, the heritability of clinically diagnosed aADHD and cADHD is very similar. Results of candidate gene as well as genome-wide molecular genetic studies in aADHD samples implicate some of the same genes involved in ADHD in children, although in some cases different alleles and different genes may be responsible for adult versus childhood ADHD. Linkage studies have been successful in identifying loci for aADHD and led to the identification of LPHN3 and CDH13 as novel genes associated with ADHD across the lifespan. In addition, studies of rare genetic variants have identified probable causative mutations for aADHD. Use of endophenotypes based on neuropsychology and neuroimaging, as well as next-generation genome analysis and improved statistical and bioinformatic analysis methods hold the promise of identifying additional genetic variants involved in disease etiology. Large, international collaborations have paved the way for well-powered studies. Progress in identifying aADHD risk genes may provide us with tools for the prediction of disease progression in the clinic and better treatment, and ultimately may help to prevent persistence of ADHD into adulthood.

Much psychiatric genetic research has focused on a 40-base pair variable number of tandem repeats (VNTR) polymorphism located in the 3′-untranslated region (3′UTR) of the dopamine active transporter (DAT) gene ( SLC6A3 ). This variant produces two common alleles with 9- and 10-repeats (9R and 10R). Studies associating this variant with in vivo DAT activity in humans have had mixed results. We searched for studies using positron emission tomography (PET) or single-photon emission computed tomography (SPECT) to evaluate this association. Random effects meta-analyses assessed the association of the 3′UTR variant with DAT activity. We also evaluated heterogeneity among studies and evidence for publication bias. We found twelve studies comprising 511 subjects, 125 from PET studies and 386 from SPECT studies. The PET studies provided highly significant evidence that the 9R allele was associated with increased DAT activity in human adults. The SPECT studies were highly heterogeneous. As a group, they suggested no association between the 3′UTR polymorphism and DAT activity. When the analysis was limited to the most commonly used ligand, [123I]β-CIT, stratification by affection status dramatically reduced heterogeneity and revealed a significant association of the 9R allele with increased DAT activity for healthy subjects. In humans, the 9R allele of the 3′UTR polymorphism of SLC6A3 regulates dopamine activity in the striatal brain regions independent of the presence of neuropsychiatric illness. Differences in study methodology account for the heterogeneous results across individual studies.

The aim of the study was to present nationally representative data on the lifetime independent association between attention deficit hyperactivity disorder (ADHD) and psychiatric co-morbidity, correlates, quality of life and treatment seeking in the USA. Data were derived from a large national sample of the US population. Face-to-face surveys of more than 34 000 adults aged 18 years and older residing in households were conducted during the 2004-2005 period. Diagnoses of ADHD, Axis I and II disorders were based on the Alcohol Use Disorder and Associated Disabilities Interview Schedule-DSM-IV version. ADHD was associated independently of the effects of other psychiatric co-morbidity with increased risk of bipolar disorder, generalized anxiety disorder, post-traumatic stress disorder, specific phobia, and narcissistic, histrionic, borderline, antisocial and schizotypal personality disorders. A lifetime history of ADHD was also associated with increased risk of engaging in behaviors reflecting lack of planning and deficient inhibitory control, with high rates of adverse events, lower perceived health, social support and higher perceived stress. Fewer than half of individuals with ADHD had ever sought treatment, and about one-quarter had ever received medication. The average age of first treatment contact was 18.40 years. ADHD is common and associated with a broad range of psychiatric disorders, impulsive behaviors, greater number of traumas, lower quality of life, perceived social support and social functioning, even after adjusting for additional co-morbidity. When treatment is sought, it is often in late adolescence or early adulthood, suggesting the need to improve diagnosis and treatment of ADHD.

A better understanding of the long-term scope and impact of the co-morbidity with oppositional defiant disorder (ODD) and conduct disorder (CD) in attention deficit hyperactivity disorder (ADHD) youth has important clinical and public health implications. Subjects were assessed blindly at baseline (mean age=10.7 years), 1-year (mean age=11.9 years), 4-year (mean age=14.7 years) and 10-year follow-up (mean age=21.7 years). The subjects' lifetime diagnostic status of ADHD, ODD and CD by the 4-year follow-up were used to define four groups (Controls, ADHD, ADHD plus ODD, and ADHD plus ODD and CD). Diagnostic outcomes at the 10-year follow-up were considered positive if full criteria were met any time after the 4-year assessment (interval diagnosis). Outcomes were examined using a Kaplan-Meier survival function (persistence of ODD), logistic regression (for binary outcomes) and negative binomial regression (for count outcomes) controlling for age. ODD persisted in a substantial minority of subjects at the 10-year follow-up. Independent of co-morbid CD, ODD was associated with major depression in the interval between the 4-year and the 10-year follow-up. Although ODD significantly increased the risk for CD and antisocial personality disorder, CD conferred a much larger risk for these outcomes. Furthermore, only CD was associated with significantly increased risk for psychoactive substance use disorders, smoking, and bipolar disorder. These longitudinal findings support and extend previously reported findings from this sample at the 4-year follow-up indicating that ODD and CD follow a divergent course. They also support previous findings that ODD heralds a compromised outcome for ADHD youth grown up independently of the co-morbidity with CD.

Stimulant medication has long been effective in treating attention-deficit/hyperactivity disorder (ADHD) and is currently the first-line pharmacological treatment for children. Both methylphenidate and amphetamine modulate extracellular catecholamine levels through interaction with dopaminergic, adrenergic and serotonergic system components; it is therefore likely that catecholaminergic molecular components influence the effects of ADHD treatment. Using meta-analysis, we sought to identify predictors of pharmacotherapy to further the clinical implementation of personalized medicine. We identified 36 studies (3647 children) linking the effectiveness of methylphenidate treatment with DNA variants. Pooled-data revealed a statistically significant association between single nucleotide polymorphisms (SNPs) rs1800544 ADRA2A (odds ratio: 1.69; confidence interval: 1.12–2.55), rs4680 COMT (odds ratio (OR): 1.40; confidence interval: 1.04–1.87), rs5569 SLC6A2 (odds ratio: 1.73; confidence interval: 1.26–2.37) and rs28386840 SLC6A2 (odds ratio: 2.93; confidence interval: 1.76–4.90), and, repeat variants variable number tandem repeat (VNTR) 4 DRD4 (odds ratio: 1.66; confidence interval: 1.16–2.37) and VNTR 10 SLC6A3 (odds ratio: 0.74; confidence interval: 0.60–0.90), whereas the following variants were not statistically significant: rs1947274 LPHN3 (odds ratio: 0.95; confidence interval: 0.71–1.26), rs5661665 LPHN3 (odds ratio: 1.07; confidence interval: 0.84–1.37) and VNTR 7 DRD4 (odds ratio: 0.68; confidence interval: 0.47–1.00). Funnel plot asymmetry among SLC6A3 studies was identified and attributed largely to small study effects. Egger’s regression test and Duval and Tweedie’s ‘trim and fill’ were used to examine and correct for publication bias. These findings have major implications for advancing our therapeutic approach to childhood ADHD treatment.

There are to date no objective clinical laboratory blood tests for psychotic disease states. We provide proof of principle for a convergent functional genomics (CFG) approach to help identify and prioritize blood biomarkers for two key psychotic symptoms, one sensory (hallucinations) and one cognitive (delusions). We used gene expression profiling in whole blood samples from patients with schizophrenia and related disorders, with phenotypic information collected at the time of blood draw, then cross-matched the data with other human and animal model lines of evidence. Topping our list of candidate blood biomarkers for hallucinations, we have four genes decreased in expression in high hallucinations states ( Fn1 , Rhobtb3 , Aldh1l1 , Mpp3 ), and three genes increased in high hallucinations states ( Arhgef9 , Phlda1 , S100a6 ). All of these genes have prior evidence of differential expression in schizophrenia patients. At the top of our list of candidate blood biomarkers for delusions, we have 15 genes decreased in expression in high delusions states (such as Drd2 , Apoe , Scamp1 , Fn1 , Idh1 , Aldh1l1 ), and 16 genes increased in high delusions states (such as Nrg1 , Egr1 , Pvalb , Dctn1 , Nmt1 , Tob2 ). Twenty-five of these genes have prior evidence of differential expression in schizophrenia patients. Predictive scores, based on panels of top candidate biomarkers, show good sensitivity and negative predictive value for detecting high psychosis states in the original cohort as well as in three additional cohorts. These results have implications for the development of objective laboratory tests to measure illness severity and response to treatment in devastating disorders such as schizophrenia.

Diagnosing attention deficit hyperactivity disorder (ADHD) in adults is difficult when diagnosticians cannot establish onset prior to the DSM-IV criterion of age 7 or if the number of symptoms does not achieve the DSM threshold for diagnosis. Previous work has assessed the validity of such diagnoses based on psychiatric co-morbidity, family history and neuropsychological functions but none of these studies have used personality as a validation criterion. We compared four groups of adults: (1) full ADHD subjects who met all DSM-IV criteria for childhood-onset ADHD; (2) late-onset subjects who met all criteria except the age at onset criterion, (3) subthreshold subjects who did not meet full symptom criteria and (4) non-ADHD subjects who did not meet any of the above criteria. Diagnoses were made by using the Structured Clinical Interview for DSM-IV (SCID) and the Temperament and Character Inventory (TCI) was used to assess personality traits. We found that full ADHD and late-onset ADHD showed similar personality profiles with significant deviations on all TCI scales except reward dependence and self-transcendence. By contrast, subthreshold cases only showed deviations on novelty seeking and self-directiveness. These data call into question the stringent age of onset of ADHD symptom criteria for adults when making retrospective diagnoses of ADHD. Subthreshold ADHD seems to be a milder form of the disorder that is consistent with dimensional views of the disorder.

Although deficient emotional self-regulation (DESR) is associated with attention deficit hyperactivity disorder (ADHD), little research investigates this association and little is known about its etiology. Family studies provide a method of clarifying the co-occurrence of clinical features, but no family studies have yet addressed ADHD and DESR in children. Subjects were 242 children with ADHD and 224 children without ADHD. DESR was operationalized using an aggregate score ≥180 and <210 in the anxious/depressed, attention and aggression scales (AAA profile) of the Child Behavior Checklist (CBCL), termed the CBCL-DESR profile. The CBCL-bipolar (CBCL-BP) profile was defined as ≥210 on the CBCL-AAA scale. We examined the familial transmission of ADHD and the CBCL-AAA scale in families selected through probands with and without these conditions. We found a linear increase in the prevalence of CBCL-DESR in siblings as indexed by the Control, ADHD, ADHD+CBCL-DESR and ADHD+CBCL-BP proband groups. While the ADHD siblings were at elevated risk for both the CBCL-DESR and CBCL-BP compared with non-ADHD siblings, a significantly higher rate of CBCL-BP in the siblings of ADHD+CBCL-BP probands was found compared with siblings of the Control probands. ADHD shows the same degree of familial transmission in the presence or absence of DESR. CBCL-DESR and CBCL-BP are familial, but further work is needed to determine if these definitions are distinctly familial or represent a continuum of the same psychopathology.