Debjani Das

A Population-Based Study of Attention Deficit/Hyperactivity Disorder Symptoms and Associated Impairment in Middle-Aged Adults

Attention deficit/hyperactivity disorder (ADHD) is the most prevalent childhood psychiatric condition. It frequently persists into adulthood and can have serious health and other adverse consequences. The majority of previous adult ADHD studies have focused on young adults so that relatively little is known about ADHD symptoms and their effects in mid and late life. In addition, effects of subclinical levels of attention deficit and hyperactivity have not been studied in detail. In this study we investigated ADHD symptoms and related impairment in a large population-based sample of middle-aged Australian adults (n = 2091; 47% male). Applying the WHO adult ADHD Self Report Screener (ASRS) we observed that 6.2% of participants had scores that were previously associated with ADHD diagnosis. No significant gender difference in the distribution of ASRS scores was observed. Multiple regression analyses indicated strong positive correlations between symptoms of ADHD and depression/anxiety and significant negative associations (p<0.01) with employment, financial stress, relationship quality, health and well-being measures in this age group. Importantly, associations were highly significant even when few ADHD symptoms were reported. Compared to the hyperactivity component, the inattention trait was particularly strongly associated and remained significant after controlling for depression/anxiety symptoms. Our study confirms previous findings and significantly adds to existing literature especially for an age-group that has not been well-studied. Our results suggest that ADHD symptoms continue to be associated with ill-health and functional impairment in mid-life and are, therefore, likely to be a major, previously unrecognized source of late-life morbidity with associated social and economic costs. Thus, there is a compelling need for better understanding and development of age-appropriate approaches to the diagnosis and treatment of ADHD in mid- to late-life.

Post-embryonic pericardial cells of Drosophila are required for overcoming toxic stress but not for cardiac function or adult development

The Drosophila heart is composed of two cell types: cardioblasts (CB) and pericardial cells (PC). Whereas CBs act to maintain rhythmic contractions, the functions of accessory PCs are not clear. The close association between these two cell types has led to speculation of a cardio-regulatory role for PCs. However, we find that viability and cardiac function are normal in larvae following post-embryonic ablation of PCs by induced cell death. Removal of PCs during the larval instars or before metamorphosis results in viable and fertile adults. Interestingly, such animals have a reduced lifespan and increased sensitivity to toxic chemicals. Thus, although PCs may have an embryonic role in cardiogenesis, they do not appear to play a part later in cardiac function as suggested. However, the role of PCs in the uptake and sequestering of toxins, their sensitivity to toxic stress and the decreased lifespan of animals without PCs indicate the importance of PCs in organismal homeostasis.

Attention deficit/hyperactivity disorder symptoms and cognitive abilities in the late-life cohort of the PATH through life study

Attention Deficit/Hyperactivity Disorder (ADHD) is a common neuropsychiatric disorder that has not been well studied in older adults. In this study we examined relationships between ADHD symptoms and cognitive ability and compared them between middle-age (MA; 48–52 years) and older-age (OA; 68–74 years) adults sampled from the same population. ADHD, mood disorder symptoms and cognitive abilities were assessed in a large population-based sample (n = 3443; 50% male). We measured current ADHD symptoms using the adult ADHD Self-Report Scale (ASRS), which we found to have the same underlying structure in both cohorts. Older adults reported significantly lower levels of ADHD symptoms and 2.2% of the OA cohort scored equal or above the ASRS cut-off score of 14 (which has been previously associated with ADHD diagnosis) compared with 6.2% of MA adults. Symptom levels were not significantly different between males and females. Using multi-group structural equation modelling we compared ADHD symptom–cognitive performance relationships between the two age groups. Generally higher ADHD symptoms were associated with poorer cognitive performance in the MA cohort. However, higher levels of inattention symptoms were associated with better verbal ability in both cohorts. Surprisingly, greater hyperactivity was associated with better task-switching abilities in older adults. In the OA cohort ADHD symptom–cognition relationships are indirect, mediated largely through the strong association between depression symptoms and cognition. Our results suggest that ADHD symptoms decrease with age and that their relationships with co-occurring mood disorders and cognitive performance also change. Although symptoms of depression are lower in older adults, they are much stronger predictors of cognitive performance and likely mediate the effect of ADHD symptoms on cognition in this age group. These results highlight the need for age-appropriate diagnosis and treatment of comorbid ADHD and mood disorders.

DRD4-exonIII-VNTR moderates the effect of childhood adversities on emotional resilience in young-adults

Most individuals successfully maintain psychological well-being even when exposed to trauma or adversity. Emotional resilience or the ability to thrive in the face of adversity is determined by complex interactions between genetic makeup, previous exposure to stress, personality, coping style, availability of social support, etc. Recent studies have demonstrated that childhood trauma diminishes resilience in adults and affects mental health. The Dopamine receptor D4 (DRD4) exon III variable number tandem repeat (VNTR) polymorphism was reported to moderate the impact of adverse childhood environment on behaviour, mood and other health-related outcomes. In this study we investigated whether DRD4-exIII-VNTR genotype moderates the effect of childhood adversities (CA) on resilience. In a representative population sample (n = 1148) aged 30–34 years, we observed an interactive effect of DRD4 genotype and CA (β = 0.132; p = 0.003) on resilience despite no main effect of the genotype when effects of age, gender and education were controlled for. The 7-repeat allele appears to protect against the adverse effect of CA since the decline in resilience associated with increased adversity was evident only in individuals without the 7-repeat allele. Resilience was also significantly associated with approach-/avoidance-related personality measures (behavioural inhibition/activation system; BIS/BAS) measures and an interactive effect of DRD4-exIII-VNTR genotype and CA on BAS was observed. Hence it is possible that approach-related personality traits could be mediating the effect of the DRD4 gene and childhood environment interaction on resilience such that when stressors are present, the 7-repeat allele influences the development of personality in a way that provides protection against adverse outcomes.

Macromolecular uptake in Drosophila pericardial cells requires rudhira function

The vertebrate reticuloendothelial system (RES) functions to remove potentially damaging macromolecules, such as excess hormones, immune-peptides and -complexes, bacterial-endotoxins, microorganisms and tumor cells. Insect hemocytes and nephrocytes - which include pericardial cells (PCs) and garland cells - are thought to be functionally equivalent to the RES. Although the ability of both vertebrate scavenger endothelial cells (SECs) and PCs to sequester colloidal and soluble macromolecules has been demonstrated the molecular mechanism of this function remains to be investigated. We report here the functional characterization of Drosophila larval PCs with important insights into their cellular uptake pathways. We demonstrate the nephrocyte function of PCs in live animals. We also develop and use live-cell assays to show that PCs take up soluble macromolecules in a Dynamin-dependent manner and colloids by a Dynamin-independent pathway. We had earlier identified Drosophila rudhira (Drudh) as a specific marker for PCs. Using RNAi mediated knock-down we show that Drudh regulates macropinocytic uptake in PCs. Our study establishes important functions for Drosophila PCs, describes methods to identify and study them, provides a genetic handle for further investigation of their role in maintaining homeostasis and demonstrates that they perform key subsets of the roles played by the vertebrate RES.

Effect of Model Choice in Genetic Association Studies: DRD4 Exon III VNTR and Cigarette Use in Young Adults

A major concern with the vast literature associating the highly polymorphic 48 bp VNTR in exon III of the human dopamine receptor D4 gene (DRD4) with various behavioral phenotypes is the lack of concordance between studies. Part of the problem arises from the absence of a universally accepted scheme for pooling the large number of low frequency genotypes into appropriate categories. Here, we investigated the effect of different pooling strategies and genetic models on the reported association between DRD4‐exIII‐VNTR polymorphism and cigarette smoking. Genotyping was performed on a large randomly selected community‐based sample of 2,274 individuals aged 20–24 years. Participants were grouped into sub‐samples based on their genotypes to test specific genetic models. Multiple regression analyses were used to assess the relationship between DRD4‐exIII‐VNTR genotype and cigarette smoking measures while controlling for confounders. While smoking status and age at start of smoking were not associated with the genotype, a significantly (P = 0.006) higher rate of cigarette consumption was observed among carriers of the 7‐repeat (7r) allele. Thus, 7r carriers were not more likely to be smokers but if they did smoke they consumed significantly more cigarettes per day than 4r carriers. Unlike previous studies this association was observed only when comparing carriers of the 7r with the 4r but not the other repeat alleles. Our study demonstrates the need for caution when grouping functionally different DRD4‐exIII‐VNTR alleles in association studies. It particularly highlights the requirement for better functional characterization of the DRD4‐exIII‐VNTR alleles for interpreting results from association studies.

Cognitive ability, intraindividual variability, and common genetic variants of catechol-O-methyltransferase and brain-derived neurotrophic factor: a longitudinal study in a population-based sample of older adults.

Genetic differences play a significant role in generating individual differences in cognitive abilities. Studies have linked common polymorphisms (valine to methionine substitution; VAL/MET) in the catechol-O-methyltransferase (COMT) and brain-derived neurotrophic factor (BDNF) to cognitive differences between individuals. However, not all studies support these associations and hence, the impact of these polymorphisms on cognition is unclear. Here, we investigated the effect of COMT VAL158MET and BDNF VAL66MET polymorphisms and their interaction on cognitive performance measured longitudinally over 8 years in a population-based sample of older adults (60-64 years at baseline; n = 400). We used multilevel models to examine differences between individuals with different genotypes in performance on psychometric tests while controlling for age, sex, and education. We observed significant main and interaction effects of COMT and BDNF genotypes on reaction time (RT) and intraindividual variability in RT (IIV-RT). Subjects with at least one copy of the COMT*MET allele (which is associated with higher prefrontal dopamine) had significantly faster RT (both simple and choice RT) and less IIV-RT in both tasks than those without the COMT*MET allele when they also carried one or more BDNF*MET alleles (which is associated with lower activity-dependent BDNF secretion). However, RT and IIV-RT did not differ significantly between the COMT genotypes in the absence of the BDNF*MET allele. These polymorphisms had no significant effect on within person change in RT or IIV-RT. Our findings indicate that the interaction between common variants of COMT and BDNF explain individual differences in RT and IIV-RT but do not explain age-related decline in these abilities.

Association of genetic risk factors with cognitive decline: the PATH through life project

We examined the association of 28 single nucleotide polymorphisms (SNPs), previously associated with dementia or cognitive performance, with tests assessing episodic memory, working memory, vocabulary, and perceptual speed in 1689 nondemented older Australians of European ancestry. In addition to testing each variant individually, we assessed the collective association of the 12-risk SNPs for late-onset Alzheimers disease using weighted and unweighted genetic risk scores. Significant associations with cognitive performance were observed for APOE ε4 allele, ABCA7-rs3764650, CR1-rs3818361, MS4A4E-rs6109332, BDNF-rs6265, COMT-rs4680, CTNNBL-rs6125962, FRMD4A-rs17314229, FRMD4A-rs17314229, intergenic SNP chrX-rs12007229, PDE7A-rs10808746, SORL1-rs668387, and ZNF224-rs3746319. In addition, the weighted genetic risk score was associated with worse performance on episodic memory. The identification of genetic risk factors, that act individually or collectively, may help in screening for people with elevated risk of cognitive decline and for understanding the biological pathways that underlie cognitive decline.

Embryonic stem cell and tissue-specific expression of a novel conserved gene, asrij.

We have identified a novel gene expressed in murine embryonic stem (ES) cells and in a restricted, tissue‐specific pattern during mouse development. The gene is also expressed in blood vessels; hence, we have named it asrij (Sanskrit; asRˆij = blood). The gene encodes a novel conserved, predicted transmembrane protein of 247 amino acids, which is localized to lysosomes and endosomes. During ES cell‐derived blood vessel formation in vitro, Asrij expression precedes and partially overlaps with the vascular markers Flk‐1 and PECAM. During development, Asrij is expressed predominantly in mouse embryonic blood vessels. The asrij transcript is alternatively spliced, and its expression is regulated in a tissue‐specific manner. An asrij splice variant that is enriched in the adult mouse brain encodes a protein of 196 amino acids. Asrij can serve as an early stem cell marker that is down‐regulated in nonvascular tissues. Our data indicate that Asrij belongs to a novel class of conserved proteins with a complex developmental profile and suggests multiple functions for the gene. Development Dynamics 227:578–586, 2003.

Regional Brain Volumes and ADHD Symptoms in Middle-Aged Adults: The PATH Through Life Study

Objective: We investigated whether volumetric differences in ADHD-associated brain regions are related to current symptoms of inattention and hyperactivity in healthy middle-aged adults and whether co-occurring anxiety/depression symptoms moderate these relationships. Method: ADHD Self-Report Scale and Brief Patient Health Questionnaire were used to assess current symptoms of inattention, hyperactivity, anxiety, and depression in a population-based sample (n = 269). Brain volumes, measured using a semi-automated method, were analyzed using multiple regression and structural equation modeling to evaluate brain volume–inattention/hyperactivity symptom relationships for selected regions. Results: Volumes of the left nucleus accumbens and a region overlapping the dorsolateral prefrontal cortex were positively associated with inattention symptoms. Left hippocampal volume was negatively associated with hyperactivity symptoms. The brain volume–inattention/hyperactivity symptom associations were stronger when anxiety/depression symptoms were controlled for. Conclusion: Inattention and hyperactivity symptoms in middle-aged adults are associated with different brain regions and co-occurring anxiety/depression symptoms moderate these brain–behavior relationships.