October 31, 2019
Executive functioning deficits persist well into adulthood for individuals with ADHD, according to a new study1 in the Journal of Attention Disorders that affirms the clinical theory that executive dysfunction is a core symptom of attention deficit hyperactivity disorder.
The small Norwegian study looked at attentional processing capacities — namely pre-attentive and executive functioning — in a group of people with and without ADHD over a 23- to 25-year period. Pre-attentive processing — the basic, preliminary stage in the brain whereby auditive and visual stimuli is analyzed — is not as well understood in relation to ADHD as is executive functioning — the controlled brain processes (like working memory) that allow us to integrate information and select optimal actions — the researchers said.
These two processes, according to the researchers, exist on “contrasting ends of [the] ‘attentional processing continuum.’” Because pre-attentive processing deficits may be precursors for brain function deficits of a higher order (like executive functioning), the study aimed to “gain insight into the long-term changes in attentional capacity” for “a clearer conception of attention dysfunction in ADHD.”
The participants, 19 male individuals with attention deficit hyperactivity disorder (ADHD or ADD) and 26 individuals without, were assessed in pre-attentive and executive functioning tasks. Researchers measured their responses to varying visual stimuli (backward masking task) and their ability to recall specific digit sequences while ignoring others (digit span distractibility test), respectively. The participants were given these assessments at three distinct points: once at around 14 years of age (study published in 1999)2, 13 years later at the first follow-up (study published in 2010)3, and at another follow up (current study) 23 to 25 years after the initial assessment.
This third stage of the study found that, even two decades after their initial assessment, individuals with ADHD exhibit greater deficits in working memory than do participants without ADHD, “suggesting a continuation of this neuropsychological deficit,” part of the study reads. ADHD participants scored roughly 10 to 15 points lower (out of 100) on executive function measures compared to the non-ADHD participants.
The participants with ADHD did not display any deficits in pre-attentional measures compared to the individuals without ADHD; this was true for all stages of the study. The ADHD group, however, did see a significant drop in performance between the second and third stages of the study. This finding, according to the researchers, suggests that “age exerts an influence on pre-attentional performance, but only for the ADHD individuals.”
No significant association between executive attention and pre-attention measures was found at this stage, contradicting previous studies that suggest an interrelatedness between the two. The researchers say this finding suggests that lower-order brain processes do not necessarily determine executive dysfunctions in ADHD, and “implies that ADHD in adulthood is primarily characterized by an impaired top-down control (in which case working memory deficits are the primary problem).”
While the study’s strengths, according to the researchers, are reflected in its long follow-up time, its high participant retention rate, and its research into pre-attention, the study is limited by its small sample size and the fact that the ADHD group consists of only males, among other factors.
“Young adults with ADHD in their mid-20s continue to be afflicted with working memory/executive attention deficits in their mid-30s,” the researchers concluded, adding, “Overall, the results are in relative consonance with Barkley’s (1997)4 theoretical framework, suggesting executive functions as a core deficit in ADHD.”
Sources
1 Torgalsbøen, B. et. al. (October 2019). Pre-attention and Working Memory in ADHD: A 25-Year Follow-Up Study. Journal of Attention Disorders. doi.org/10.1177/1087054719879491.
2 Øie, M., Rund, B. R. (1999). Neuropsychological deficits in adolescent-onset schizophrenia compared with attention deficit. The American Journal of Psychiatry, 156, 1216-1222. doi:10.1176/ajp.156.8.1216
3 Øie, M., Sundet, K., Rund, B. R. (2010). Neurocognitive decline in early-onset schizophrenia compared with ADHD and normal controls: Evidence from a 13-year follow-up study. Schizophrenia Bulletin, 36, 557-565. doi:10.1093/schbul/sbn127
4 Barkley, R. A. (1997). Behavioral inhibition, sustained attention, and executive functions: Constructing a unifying theory of ADHD. Psychological Bulletin, 121, 65-94.