Common cause versus dynamic mutualism: Insights into ADHD's common comorbidities
Zheyue Peng, Ashley L. Watts · 2026 · 2 citationsRead the paper
Abstract Background Contemporary classification systems differ in their conceptualization of ADHD as either an externalizing or neurodevelopmental condition, with both perspectives promoting the common cause model as an explanation of ADHD's comorbidity. An alternative theory, dynamic mutualism, proposes that ADHD's comorbidity emerges through reciprocal interactions among symptoms over time, as opposed to a common cause. Methods We tested the common cause and the dynamic mutualism theories in explaining the associations between aspects of ADHD (i.e., ADHD, inattention, hyperactivity/impulsivity, cognitive disengagement) and the neurodevelopmental and externalizing spectra across four waves of the Adolescent Brain Cognitive Development (ABCD) Study data ( n = 11,878 youths aged 9–10 at baseline; 48% female). Results Results largely supported the common cause theory in explaining the developmental links between ADHD and both the externalizing and neurodevelopmental spectra. Findings varied across ADHD subdimensions, although not substantially, with hyperactivity/impulsivity more closely linked to the externalizing spectrum and cognitive disengagement more closely linked to the neurodevelopmental spectrum. Conclusion ADHD is best conceptualized as a disorder that bridges both the externalizing and neurodevelopmental domains, rather than fitting exclusively within either category. Given the assessment structure of the ABCD Study, there was more support for the common cause model compared with dynamic mutualism.
What the full text shows
Tested in real conditions- The common cause model was favored over dynamic mutualism in explaining the developmental links between ADHD and both externalizing and neurodevelopmental spectra. (Youth aged 9–10 at baseline across four waves of ABCD Study data)
- Hyperactivity/impulsivity showed the strongest association with the externalizing spectrum. (Between-person level analysis)
- Cognitive disengagement showed the strongest between-person ties to the neurodevelopmental spectrum. (Between-person level analysis)
- Within-person cross-sectional associations between ADHD and the externalizing spectrum were moderate to strong and stable over time. (Within-person level analysis)
- Within-person cross-sectional associations between ADHD and the neurodevelopmental spectrum decreased steadily over time. (Within-person level analysis)
- Setup
- 11,878 youths (48% female) aged 9–10 at baseline from the Adolescent Brain Cognitive Development (ABCD) Study, tracked over four assessment waves.
- How
- The researchers used a latent curve model with structured residuals (LCM-SR) to partition between- and within-person variance and model developmental trajectories. They analyzed four waves of longitudinal data using the Child Behavioral Checklist (CBCL) to measure ADHD subdimensions and psychopathology spectra.
- Limitations
- Common method variance and evaluative consistency bias may have inflated correlations, exaggerating support for the common cause model. · The absence of cross-lagged associations may be due to a mismatch between the 1-year assessment interval and the actual causal process. · The neurodevelopmental spectrum assessment relied solely on CBCL symptoms, excluding specific measures for Tourette's or motor disorders.
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it