Age and DRD4 Genotype Moderate Associations Between Stimulant Treatment History and Cortex Structure in Attention-Deficit/Hyperactivity Disorder.
Attention-deficit/hyperactivity disorder (ADHD) has been associated with dopaminergic imbalance and subtle volume decreases in the brain. Stimulants acutely enhance dopaminergic neurotransmission. Long-term effects of prolonged manipulation of the dopaminergic system on brain structure remain poorly understood; they could be beneficial or unfavorable and could be moderated by common genetic variants and/or age.



In a large observational ADHD cohort study (N = 316), the effects of cumulative stimulant treatment, genotype (for DAT1 haplotype and DRD4 variants), and treatment-by-genotype interactions on striatal, frontal, and hippocampal volumes and their interactions with age were evaluated.



No main effects of treatment were found. Associations between treatment and bilateral frontal and left hippocampal volume depended on DRD4 genotype and age. At a younger age and lower treatment levels, but not at a younger age and higher treatment levels, carriers of the DRD4 7R allele showed decreased frontal cortex volumes. At an older age, carriers and non-carriers showed smaller frontal volumes irrespective of treatment history. Left hippocampal volume was similar to that in controls at average treatment levels and increased with treatment only in carriers of the DRD4 risk allele and at a younger age. No interaction effects were found in the striatum.



Carriers of the DRD4 risk allele at a younger age might be sensitive to cortical remodeling after stimulant treatment. The cross-sectional nature of this study warrants cautious interpretation of age effects. The present findings, although of small effect size, might ultimately contribute to optimal care for individuals with ADHD.
University of Groningen and University Medical Center Groningen, Groningen, the Netherlands. Electronic address: ljs82@medschl.cam.ac.uk.
Lizanne J S
LJ
Schweren
University of Groningen and University Medical Center Groningen, Groningen, the Netherlands.
Catharina A
CA
Hartman
VU University Amsterdam, the Netherlands.
Dirk J
DJ
Heslenfeld
VU University Amsterdam, the Netherlands.
Annabeth P
AP
Groenman
Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands.
Barbara
B
Franke
VU University Amsterdam, the Netherlands.
Jaap
J
Oosterlaan
Radboud University Medical Center, Donders Institute for Brain, Cognition and Behavior, Nijmegen, the Netherlands; Karakter Child and Adolescent Psychiatry University Center.
Jan K
JK
Buitelaar
University of Groningen and University Medical Center Groningen, Groningen, the Netherlands.
Pieter J
PJ
Hoekstra
D000293:Adolescent; D000367:Age Factors; D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology* / Q000523:psychology; D054316:Biomarkers, Pharmacological; D002540:Cerebral Cortex / Q000187:drug effects* / Q000473:pathology*; D002648:Child; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D050638:Receptors, Dopamine D4 / Q000097:blood / Q000235:genetics*; D055815:Young Adult
D054316:Biomarkers, Pharmacological; C493599:DRD4 protein, human; D050638:Receptors, Dopamine D4
DRD4; attention-deficit/hyperactivity disorder; gene–environment interaction; magnetic resonance imaging; stimulant treatment