Analysis of structural brain asymmetries in attention-deficit/hyperactivity disorder in 39 datasets

OBJECTIVE

Some studies have suggested alterations of structural brain asymmetry in attention-deficit/hyperactivity disorder (ADHD), but findings have been contradictory and based on small samples. Here, we performed the largest ever analysis of brain left-right asymmetry in ADHD, using 39 datasets of the ENIGMA consortium.

METHODS

We analyzed asymmetry of subcortical and cerebral cortical structures in up to 1,933 people with ADHD and 1,829 unaffected controls. Asymmetry Indexes (AIs) were calculated per participant for each bilaterally paired measure, and linear mixed effects modeling was applied separately in children, adolescents, adults, and the total sample, to test exhaustively for potential associations of ADHD with structural brain asymmetries.

RESULTS

There was no evidence for altered caudate nucleus asymmetry in ADHD, in contrast to prior literature. In children, there was less rightward asymmetry of the total hemispheric surface area compared to controls (t = 2.1, p = .04). Lower rightward asymmetry of medial orbitofrontal cortex surface area in ADHD (t = 2.7, p = .01) was similar to a recent finding for autism spectrum disorder. There were also some differences in cortical thickness asymmetry across age groups. In adults with ADHD, globus pallidus asymmetry was altered compared to those without ADHD. However, all effects were small (Cohen's d from -0.18 to 0.18) and would not survive study-wide correction for multiple testing.

CONCLUSION

Prior studies of altered structural brain asymmetry in ADHD were likely underpowered to detect the small effects reported here. Altered structural asymmetry is unlikely to provide a useful biomarker for ADHD, but may provide neurobiological insights into the trait.

Acute ingestion of alcohol and cardiac autonomic modulation in healthy volunteers

Arrhythmogenic effects of alcohol may be intermediated by its effects over heart rate variability (HRV). Most studies about the effects of alcohol over HRV were observational and did not explore the temporal influence of alcohol ingestion over autonomic modulation. The aim of this study was to verify if an acute ingestion of alcohol has a time-dependent influence over time-domain indices of HRV. The effect of the ingestion of 60 g of ethanol or placebo over autonomic modulation was compared in healthy men (35 per group), with 18-25 years of age, before and during 17 h after ingestion. Alcohol promoted a fall in the standard deviation of all normal R-R intervals, root mean square of successive differences, and percentage of pairs of adjacent R-R intervals differing by more than 50 ms and in two indices of the three-dimensional return map, by a period up to 10 h after the ingestion of alcohol, accompanied by an increase in heart rate. The indices returned to values similar of the control group 10 h after ingestion. The effects over HRV indices were attenuated by adjustment for heart rate. The ingestion of alcohol induces a broad cardiovascular adaptation secondary to vagal withdrawal and sympathetic activation that may be responsible for arrhythmogenic effects of alcohol ingestion.

Heterogeneity in early onset alcoholism suggests a third group of alcoholics

Data from 141 Brazilian male alcoholics were investigated with the objective of further exploring the heterogeneity of alcoholism and to replicate previous studies. A set of seven variables was studied by different cluster analyses to test hypotheses with two, three, and four groups. The results suggested that the best solution showed three groups of alcoholics, two of them similar to those previously described and a third relatively similar to type 2, but with lower scores in harm avoidance, more positive impact of life events, higher proportion of alcoholic relatives, less frequent use of antianxiety drugs, and less delirium tremens. These results reinforced the model with three groups and may be useful in the delineation of new etiology and treatment studies.

The TaqI A1 allele of the dopamine D2 receptor gene and alcoholism in Brazil: association and interaction with stress and harm avoidance on severity prediction

Allele and genotype frequencies of the TaqI A polymorphism of dopamine D2 receptor (DRD2) gene were compared in 115 alcohol-dependent Brazilian males and 114 ethnically matched controls. Regression analyses were performed to test for an interactive effect between the DRD2 TaqI A1 allele and measures of stress and harm avoidance on severity of alcoholism and number of antisocial personality symptoms. A slightly positive association of DRD2 TaqI A1 genotypes with alcoholism was observed, by standard and molecular heterosis approaches. The DRD2 TaqI A1 allele showed significant interaction with stress and harm avoidance in predicting the severity of physiologic dependence, and with harm avoidance for the number of antisocial personality symptoms. Separate partial correlation analyses showed that stress-related variables were significantly correlated with severity scores in alcoholics with the allele, but not in those without it. This is the first demonstration of an interaction between a genetic polymorphism and stress-related measures on the severity of psychiatric disorders.

Dopamine D4 receptor gene and personality dimensions in Brazilian male alcoholics

The presence of the seven-repeat allele of the VNTR in the exon 3 of the dopamine D4 receptor gene (DRD4) has been associated in healthy subjects to the personality trait of novelty seeking. The present study focuses these observations on a sample of Brazilian male alcoholics, evaluated on the temperament dimensions originally described by Cloninger. The genotypes observed are in agreement with those expected under Hardy-Weinberg equilibrium. Subjects with the seven-repeat allele manifest lower harm avoidance scores. No significant differences between subjects with or without the seven-repeat allele in the scores of novelty seeking or reward dependence were observed. The lack of association between novelty seeking and the DRD4 exon 3 polymorphism is further corroborated by the fact that the comorbid antisocial personality disorder is not associated to the presence of the seven-repeat allele. These results could be explained by a biological connection between the personality dimensions of novelty seeking and harm avoidance.

Alcoholism in Brazil--the role of personality and susceptibility to stress

One hundred alcohol-dependent Brazilian males were investigated in relation to variables dealing with the course of alcoholism, family history and behaviour. Seven of the most representative were standardized and then subjected to a factor analysis. The factors thus obtained were afterwards included in a cluster analysis, which identified three groups of alcoholics. Two of these groups agree with those established on recent previous classifications, while the third revealed a characteristic not identified in these typologies: lower levels of stress. Other distinctive features were lower scores of harm avoidance and higher proportion of alcoholic relatives. In relation to other conditions these subjects presented intermediary values, suggesting that they may constitute an intermediate between the two other, polar types. It will be important to verify if these results are confirmed in populations with biological and cultural characteristics different from the Brazilian one.

Bilateral femoral hypoplasia associated with Rokitansky sequence: another example of a mesodermal malformation spectrum?

We report on a woman with bilateral femoral hypoplasia and Rokitansky sequence, malformations that up to now had not been described together. There are no other cases in the family, and no history of prenatal teratogen exposure. This case may be part of a mesodermal malformation spectrum.