Comorbid externalising behaviour in AD/HD: evidence for a distinct pathological entity in adolescence

Comparison of Brain Function Between Medication-Naïve ADHD with and without Comorbidity in Chinese Children Using Resting-State fNIRS

Background

This study used functional near-infrared spectroscopy (fNIRS) to investigate brain activation patterns in children with attention deficit hyperactivity disorder (ADHD) with and without additional comorbidities to identify disease-related biomarkers by the neuroimaging that will facilitate to make a diagnosis decision.

Methods

In this study, 165 medication-naive children aged 7 to 15 years were recruited and categorized into four groups: ADHD, ADHD with learning disabilities (ADHD&LD), ADHD with oppositional defiant disorder (ADHD&ODD), and healthy controls. A multichannel fNIRS system was used to monitor hemodynamic changes at rest state in the prefrontal and temporal lobes of the brain. The amplitude of a low-frequency fluctuation (ALFF) matrix was calculated by summation and averaging of the square root of the signal power spectrum. One-way analysis of variance was used to identify statistical differences between channels.

Results

All ADHD children presented significantly higher ALFF values in different brain regions when compared with the healthy controls. Patients with ADHD&LD exhibited higher ALFF values in the medial prefrontal cortex (P Ch38 = .01, P Ch48 = .01), temporal cortex (P Ch22 = .04, P Ch41 = .002, P Ch51 = .001), and the left ventrolateral prefrontal cortex (P Ch39 = .0009, P Ch50 = .001), whereas ADHD&ODD children were not significantly different to those diagnosed with ADHD.

Conclusions

ADHD with learning disabilities (LD) possessed a different pathogenesis from ADHD, manifested as lower functional brain activity in the medial prefrontal cortex, temporal cortex, and the left ventrolateral prefrontal cortex, while ADHD&ODD did not present significant changes compared with ADHD. ODD-related symptoms may be part of ADHD symptoms rather than being an independent disorder.

Relationship between intraindividual auditory and visual attention in children with ADHD

BACKGROUND AND AIM

Most previous attention-deficit/hyperactivity disorder (ADHD) studies have used only a single sensory modality (usually vision) to investigate attentional problems, although patients with ADHD might display deficits of auditory attention similar to their visual attention. This study explored intraindividual auditory and visual attention in children with and without ADHD to examine the relationship between these two dimensions of attention.

METHODS

Attentional performances of 140 children (70 children with ADHD and 70 typically developing peers) were measured through the Test of Variables of Attention (TOVA) in the present study.

RESULTS

For both groups, most attentional indices showed significant differences between the two modalities (d ranging from 0.32 to 0.72). The correlation coefficients of most of the attentional variables in children with ADHD were lower than their typically developing peers. All attentional indices of children with ADHD (ranging from 12.8%-55.7%) were much higher than those of their typically developing peers (ranging from 1.4%-8.6%).

CONCLUSION

These results not only indicate that typically developing children display more consistent attentional performance, but also support the view that children with ADHD may show attention deficiency in one modality but not necessarily in the other.

Massive withdrawal symptoms and affective vulnerability are associated with variants of the CHRNA4 gene in a subgroup of smokers

Heterogeneous phenotypes of complex disorders pose a great challenge for genetic association studies and for the development of personalized treatment strategies. Cluster analysis of phenotypic data has been recently proposed as a reliable auxiliary method for such studies. A cohort of 236 treatment-seeking smokers was investigated after overnight nicotine abstinence. Alpha4 nicotinic acetylcholine receptor (nAChR) subunit-related phenotypes were assessed by the Fagerström Test for Nicotine Dependence (FTND), exhaled carbon monoxide (CO) measurements, the Minnesota Nicotine Withdrawal Scale (MNWS) and the Zung Self-Rating Depression Scale (ZSDS). Seven tag SNPs (single-nucleotide polymorphisms) across CHRNA4 (the gene encoding alpha4 subunit of the nicotinic acetylcholine receptor) were genotyped and two-step cluster analysis was used for phenotypic cluster characterization. Haplotype estimation was determined by HapStat module of R 2.0 software. Three different phenotypic clusters were identified and the C3 cluster was characterized by the highest ZSDS and MNWS scores compared to others. Furthermore, lifetime prevalence of major depression was significantly higher in the C3 cluster (p = 0.019). In genetic association tests, this cluster was also significantly associated with rs3787138 genotypes (p = 0.004) while haplotype analyses of three SNPs (rs3787138, rs1044396, rs3787140) revealed that the risk for C3 phenotype was almost three times higher in GCC haplotype carriers compared to others (pperm = 0.013). This is the first report on a significant association between CHRNA4 variants and a subgroup of smokers characterized by massive withdrawal symptoms and affective vulnerability. Identification of such a phenotypic cluster can be a pivotal step for further pharmacogenetic studies on ligands of the alpha4 nAChR subunit. Our results suggest that performing cluster analysis in genetic association studies can be proposed for complex disorders.