Parental age and developmental milestones: pilot study indicated a role in understanding ADHD severity in Indian probands

Specific dopaminergic genetic variants influence impulsivity, cognitive deficit, and disease severity of Indian ADHD probands

BACKGROUND

Impulsivity (Imp), being one of the cardinal symptoms of Attention Deficit Hyperactivity Disorder (ADHD), often leads to inappropriate responses to stimuli. Since the dopaminergic system is the primary target for pharmaceutical intervention in ADHD, we investigated the association between ADHD-related Imp and functional gene variants of the dopamine transporter (SLC6A3) and catechol-O-methyltransferase involved in dopamine clearance.

METHODS AND RESULTS

Indo-Caucasoid families with ADHD probands (N = 217) were recruited based on the Diagnostic and Statistical Manual of Mental Disorders (DSM). Imp of the probands was assessed using the Domain Specific Imp Scale for Children and DSM. Peripheral blood was collected after obtaining informed written consent for participation, genomic DNA was isolated, and target sites were genotyped by DNA sequencing. The association of genetic variants with Imp was examined by the Quantitative trait analysis (QTA) and Analysis of variance (ANOVA). Post-Hoc analysis following QTA and ANOVA showed significant associations of rs2254408, rs2981359, and rs2239393 with different domains of Imp (P < 0.05). Various haplotypic combinations also showed statistically significant associations with Imp (P < 0.05). Multifactor dimensionality reduction models revealed strong effects of the variants on Imp. ADHD probands harboring the risk alleles exhibited a deficit in performance during cognitive assessment. Longitudinal follow-up revealed a significant association of rs2254408 with trait persistence.

CONCLUSION

The present study indicates the influence of the studied genetic variants on ADHD-associated imp, executive deficit, and disease persistence. Thus, these variants may be helpful as predictors for the success of individual therapeutic sessions during cognitive training.

Parental Age and the Risk of ADHD in Offspring: A Systematic Review and Meta-Analysis

Evidence has suggested that parental age at birth is a risk factor of offspring attention deficit/hyperactivity disorder (ADHD). We conducted a meta-analysis of observational studies investigating the association between parental age and offspring ADHD. We conducted a systematic search that followed the recommended guidelines for performing meta-analyses on PUBMED, EMBASE, and Web of Science up to 8 April 2021. We calculated pooled risk estimates from individual age with and without adjusting for possible confounding factors. Dose–response analysis for parental age and ADHD risk was performed. Eleven studies were selected in this meta-analysis, which included 111,101 cases and 4,417,148 participants. Compared with the reference points, the lowest parental age category was associated with an increased risk of ADHD in the offspring, with adjusted odds ratios (ORs) of 1.49 (95% confidence intervals (95%CI) 1.19–1.87) and 1.75 (95%CI 1.31–2.36) for the mother and father, respectively. The highest parental age was statistically insignificant, with adjusted ORs of 1.11 (95%CI 0.79–1.55) and 0.93 (95%CI 0.70–1.23) for mother and father separately. Dose–response analysis indicated a non-linear relationship of parental age with offspring ADHD, with the lowest ADHD risk at 31–35 years old. The results of this meta-analysis support an association between young parental age and the risk of ADHD. More high-quality studies are needed to establish whether the association with parental age is causal.