The authors of a study in the Journal of Abnormal Child Psychology found an association between early childhood stress, attention-deficit/hyperactivity disorder symptoms, and volume of certain areas of the brain.
Previous research has suggested that the etiology of attention-deficit/hyperactivity disorder is neither purely genetic nor environmental. Heritability of the disorder has been estimated at 75%; however, examination of environmental factors is ongoing.
The authors identified 214 children aged 9.11 to 13.98 years, with boys and girls matched for pubertal stage; thus, girls were, on average, older. Those with a history of a major neurologic or medical illness or who could not receive a magnetic resonance imaging scan were excluded.
Parents completed the Child Behavior Checklist. According to the checklist’s Attention Problems subscale, 15% of participants met the threshold for clinical concern, although the authors pointed out that the subscale does not map exactly to the Diagnostic and Statistical Manual of Mental Disorders definition of attention-deficit/hyperactivity disorder.
The self-reported Traumatic Events Screening Inventory for Children was used to determine the number of stressors participants experienced at <6 years and ≥6 years, with the authors interested in whether the timing of such events had any particular effect. Although the authors discovered no “sensitive period,” the number of events was moderately associated with the severity of attention-deficit/hyperactivity disorder symptoms.
The authors also used tensor-based morphometry to examine variation in brain structure, a technique that has been applied previously to populations with dementia, autism spectrum disorders, and human immunodeficiency virus. They were able to identify a few areas of interest in the brain — the posterior internal capsule, inferior temporal gyrus, and transverse temporal gyrus — where volume was associated with both the number of stressors and symptom severity.
In interpreting their findings, the authors stated that, “it may be worthwhile to consider whether reactions to trauma are responsible for elevated symptoms of [attention-deficit/hyperactivity disorder] or if [attention-deficit/hyperactivity disorder] is elevated even after accounting for [posttraumatic stress disorder].” They also pointed out their use of quantitative, not qualitative, measures of early childhood stressors as a potential limitation, as well as the possibility of omission in self-reported events by children.
Humphreys KL, Watts EL, Dennis EL, King LS, Thompson PM, Gotlib IH. Stressful life events, ADHD symptoms, and brain structure in early adolescence [published online May 21, 2018]. J Abnorm Child Psychol. doi:10.1007/s10802-018-0443-5