An association study of sequence variants in the forkhead box P2 (FOXP2) gene and adulthood attention-deficit/hyperactivity disorder in two European samples.

OBJECTIVES: Attention-deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder manifesting as symptoms of inattention, hyperactivity, and/or impulsivity. Learning disabilities co-occur with ADHD in 20-30% of cases and this high co-occurrence raises the possibility of a common etiological background. Forkhead box P2 (FOXP2) encodes a transcription factor involved in speech and language impairment and in the control of the corticobasal ganglia circuits known to be relevant in ADHD, suggesting a possible role of FOXP2 in ADHD. Our aim was to carry out an association study between FOXP2 and adulthood ADHD. METHODS: We carried out a case-control association study in 643 adult ADHD patients and 619 controls from Germany and in 361 adult ADHD patients and 442 controls from Spain with 12 tagging single nucleotide polymorphisms covering the FOXP2 gene. RESULTS: The single-marker and multiple-marker analyses showed an association between FOXP2 and combined ADHD in the German cohort [rs12533005: P=0.0033; odds ratio=1.30 (1.09-1.56); rs12533005/rs1229761: P=4.1e-04; odds ratio=1.38 (1.15-1.66)]. These positive results, however, were not confirmed in the Spanish sample. CONCLUSION: Although these preliminary findings provide a tentative evidence for the contribution of FOXP2 to ADHD and suggest common genetic factors for this psychiatric disorder and learning disabilities, they should be interpreted with caution. Further studies in larger samples are needed to clarify the role of this transcription factor in ADHD.

DIRAS2 is associated with adult ADHD, related traits, and co-morbid disorders.

Several linkage analyses implicated the chromosome 9q22 region in attention deficit/hyperactivity disorder (ADHD), a neurodevelopmental disease with remarkable persistence into adulthood. This locus contains the brain-expressed GTP-binding RAS-like 2 gene (DIRAS2) thought to regulate neurogenesis. As DIRAS2 is a positional and functional ADHD candidate gene, we conducted an association study in 600 patients suffering from adult ADHD (aADHD) and 420 controls. Replication samples consisted of 1035 aADHD patients and 1381 controls, as well as 166 families with a child affected from childhood ADHD. Given the high degree of co-morbidity with ADHD, we also investigated patients suffering from bipolar disorder (BD) (n=336) or personality disorders (PDs) (n=622). Twelve single-nucleotide polymorphisms (SNPs) covering the structural gene and the transcriptional control region of DIRAS2 were analyzed. Four SNPs and two haplotype blocks showed evidence of association with ADHD, with nominal p-values ranging from p=0.006 to p=0.05. In the adult replication samples, we obtained a consistent effect of rs1412005 and of a risk haplotype containing the promoter region (p=0.026). Meta-analysis resulted in a significant common OR of 1.12 (p=0.04) for rs1412005 and confirmed association with the promoter risk haplotype (OR=1.45, p=0.0003). Subsequent analysis in nuclear families with childhood ADHD again showed an association of the promoter haplotype block (p=0.02). rs1412005 also increased risk toward BD (p=0.026) and cluster B PD (p=0.031). Additional SNPs showed association with personality scores (p=0.008-0.048). Converging lines of evidence implicate genetic variance in the promoter region of DIRAS2 in the etiology of ADHD and co-morbid impulsive disorders.

Cross-disorder analysis of bipolar risk genes: further evidence of DGKH as a risk gene for bipolar disorder, but also unipolar depression and adult ADHD.

Recently, several genome-wide association studies (GWAS) on bipolar disorder (BPD) suggested novel risk genes. However, only few of them were followed up and further, the specificity of these genes is even more elusive. To address these issues, we genotyped SNPs in ANK3, CACNA1C, CMTM8, DGKH, EGFR, and NPAS3, which were significantly associated with BPD in previous GWAS, in a sample of 380 BPD patients. Replicated SNPs were then followed up in patients suffering from unipolar depression (UPD; n=387) or adult attention-deficit/hyperactivity disorder (aADHD; n=535). While we could not confirm an association of ANK3, CACNA1C, and EGFR with BPD, 10 SNPs in DGKH, CMTM8, and NPAS3 were nominally associated with disease, with two DGKH markers surviving correction for multiple testing. When these were followed up in UPD and aADHD, seven DGKH SNPs were also associated with UPD, while one SNP each in NPAS3 and CMTM8 and four in DGKH were linked to aADHD. Furthermore, a DGKH haplotype consisting of rs994856/rs9525580/rs9525584 GAT was associated with all disorders tested, while the complementary AGC haplotype was protective. The corresponding haploblock spans a 27-kb region covering exons coding for amino acids 65-243, and thus might include functional variants yet to be identified. We demonstrate an association of DGKH with BPD, UPD, and aADHD by applying a two-stage design. These disorders share the feature of mood instability, so that this phenotype might be associated with genetic variation in DGKH.

Exploring DRD4 and its interaction with SLC6A3 as possible risk factors for adult ADHD: a meta-analysis in four European populations.

Attention-deficit hyperactivity disorder (ADHD) is a common behavioral disorder affecting about 4-8% of children. ADHD persists into adulthood in around 65% of cases, either as the full condition or in partial remission with persistence of symptoms. Pharmacological, animal and molecular genetic studies support a role for genes of the dopaminergic system in ADHD due to its essential role in motor control, cognition, emotion, and reward. Based on these data, we analyzed two functional polymorphisms within the DRD4 gene (120 bp duplication in the promoter and 48 bp VNTR in exon 3) in a clinical sample of 1,608 adult ADHD patients and 2,352 controls of Caucasian origin from four European countries that had been recruited in the context of the International Multicentre persistent ADHD CollaboraTion (IMpACT). Single-marker analysis of the two polymorphisms did not reveal association with ADHD. In contrast, multiple-marker meta-analysis showed a nominal association (P = 0.02) of the L-4R haplotype (dup120bp-48bpVNTR) with adulthood ADHD, especially with the combined clinical subtype. Since we previously described association between adulthood ADHD and the dopamine transporter SLC6A3 9R-6R haplotype (3'UTR VNTR-intron 8 VNTR) in the same dataset, we further tested for gene × gene interaction between DRD4 and SLC6A3. However, we detected no epistatic effects but our results rather suggest additive effects of the DRD4 risk haplotype and the SLC6A3 gene.

Altered frontal and temporal brain function during olfactory stimulation in adult attention-deficit/hyperactivity disorder.

OBJECTIVE: Olfactory processing depends on dopamine metabolism and orbitofrontal cortex functioning, both known to be disturbed in attention-deficit/hyperactivity disorder (ADHD). Some investigations suggested alterations in olfactory processing (identification and sensitivity) in childhood and adult ADHD. METHODS: In the present study we investigated olfactory function (Sniffin' Sticks) of 29 adult patients with ADHD (17 combined, 11 inattentive, and 1 hyperactive/impulsive subtype) and 29 controls matched for sex, handedness, age, intelligence, and education. Additionally, we measured frontal, temporal, and somatosensory cortical activity during olfactory perception. This was performed with functional near-infrared spectroscopy (fNIRS) during presentation of 2-phenylethanol (olfactory stimulant) and linalool (mixed olfactory/trigeminal stimulant) in two concentrations each. RESULTS: Adult patients with ADHD and controls did not differ in sensitivity for and discrimination and identification of olfactory stimuli. Functional brain imaging measures with fNIRS generally revealed diminished activation in olfaction-associated brain regions in patients with ADHD. Only for a high concentration of linalool, oxygenated haemoglobin (O2Hb) concentrations in patients were similar to controls (significant increase in the temporal, somatosensory, and inferior-frontal cortex). O2Hb concentrations in active brain regions positively correlated with ADHD symptoms during childhood and trait impulsivity. These effects were carried for the subgroup with combined subtype. CONCLUSIONS: Although we could not replicate altered clinical performance in ADHD, our fNIRS findings suggest an association of cortical olfactory processing with hyperactivity and impulsivity in adult ADHD.

Common variants in the TPH1 and TPH2 regions are not associated with persistent ADHD in a combined sample of 1,636 adult cases and 1,923 controls from four European populations.

The tryptophan hydroxylase 1 and 2 (TPH1 and TPH2) genes encode the rate-limiting enzymes in the serotonin biosynthesis. Genetic variants in both genes have been implicated in several psychiatric disorders. For attention-deficit/hyperactivity disorder (ADHD) in children, the results are conflicting, and little is known about their role in adult ADHD patients. We therefore first genotype-tagged all common variants within both genes in a Norwegian sample of 451 patients with a diagnosis of adult ADHD and 584 controls. Six of the single nucleotide polymorphisms (SNPs) were subsequently genotyped in three additional independent European Caucasian samples of adult ADHD cases and controls from the International Multicenter persistent ADHD Collaboration (IMpACT). None of the SNPs reached formal study-wide significance in the total meta-analysis sample of 1,636 cases and 1,923 controls, despite having a power of >80% to detect a variant conferring an OR = 1.25 at P = 0.001 level. Only the TPH1 SNP rs17794760 showed nominal significance [OR = 0.84 (0.71-1.00), P = 0.05]. In conclusion, in the single largest ADHD genetic study of TPH1 and TPH2 variants presented to date (n = 3,559 individuals), we did not find consistent evidence for a substantial effect of common genetic variants on persistent ADHD.

Case-control study of six genes asymmetrically expressed in the two cerebral hemispheres: association of BAIAP2 with attention-deficit/hyperactivity disorder.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is a childhood-onset neuropsychiatric disease that persists into adulthood in at least 30% of patients. There is evidence suggesting that abnormal left-right brain asymmetries in ADHD patients may be involved in a variety of ADHD-related cognitive processes, including sustained attention, working memory, response inhibition and planning. Although mechanisms underlying cerebral lateralization are unknown, left-right cortical asymmetry has been associated with transcriptional asymmetry at embryonic stages and several genes differentially expressed between hemispheres have been identified. METHODS: We selected six functional candidate genes showing at least 1.9-fold differential expression between hemispheres (BAIAP2, DAPPER1, LMO4, NEUROD6, ATP2B3, and ID2) and performed a case-control association study in an initial Spanish sample of 587 ADHD patients (270 adults and 317 children) and 587 control subjects. RESULTS: The single- and multiple-marker analysis provided evidence for a contribution of BAIAP2 to adulthood ADHD (p = .0026 and p = .0016, respectively). We thus tested BAIAP2 for replication in two independent adult samples from Germany (639 ADHD patients and 612 control subjects) and Norway (417 ADHD cases and 469 control subjects). While no significant results were observed in the Norwegian sample, we replicated the initial association between BAIAP2 and adulthood ADHD in the German population (p = .0062). CONCLUSIONS: Our results support the participation of BAIAP2 in the continuity of ADHD across life span, at least in some of the populations analyzed, and suggest that genetic factors potentially influencing abnormal cerebral lateralization may be involved in this disorder.

The psychopathological and psychosocial outcome of early-onset schizophrenia: preliminary data of a 13-year follow-up.

BACKGROUND: Relatively little is known about the long-term psychopathological and psychosocial outcome of early-onset schizophrenia. The existing literature describes more severe courses of illness in these patients compared with adult-onset schizophrenia. This article reports preliminary data of a study exploring the outcome of early-onset schizophrenia 13.4 years (mean) after first admission. Predictors for interindividual outcomes were investigated. METHODS: We retrospectively assessed 27 former patients (mean age at first admission 15.5 years, SD = 2.0) that were consecutively admitted to the Department of Child and Adolescent Psychiatry at the University of Wuerzburg between 1990 and 2000. A multidimensional approach was chosen to assess the outcome consisting of a mail survey including different questions about psychopathological symptoms, psychosocial parameters, and standardized self-reports (ESI and ADS). RESULTS: Concerning the psychopathological outcome, 22.2% reported having acute schizophrenic symptoms. Almost one third (30.8%) described symptoms of depression and 37.0% reported having tried to commit suicide or seriously thought about it. 77.8% of the former patients were still in outpatient treatment. Compared to the general population, the number of patients without a school graduation was relatively high (18.5%). Almost half of participants still live with their parents (48.1%) or in assisted or semi-assisted living conditions (33.3%). Only 18.5% were working in the open market. CONCLUSION: Schizophrenia with an early onset has an unfavourable prognosis. Our retrospective study of the psychopathological and psychosocial outcome concludes with a generally poor rating.