A – 29 The Effect of Age on Symptom Severity in Individuals with Attention Deficit Hyperactivity Disorder

Objective To explore whether a relationship exists between age and self-reported symptom severity in individuals with ADHD. Method The data for this study was derived from a large de-identified single-photon emission computed tomography (SPECT) database. Of these scans, the sample consisted of medication-free individuals diagnosed with ADHD (noverall=152). Participants with select comorbid diagnoses were excluded from the final sample. The ADHD child group (< 18 years) had an average age of 10.84 (SD=3.96) years (73.7% males, 25% females, and 1.3% unspecified), and the ADHD adult group had an average age of 36.79 (SD=12.61) years (52.6% males and 47.4% females). Linear regression analysis was conducted. The predictor variable was age, and the dependent variable was symptom severity (summed hyperactivity/inattention scores on a self-report questionnaire). Alpha level for the analysis was 0.05. Results Age was found to significantly predict symptom severity and predicted 38.6% of the variance in hyperactivity/impulsivity symptom severity [R2=0.386, F (1,140) =86.864, p< 0.001]; subsequently, with each one-year increase in age, rCBF levels were found to increase by 0.719 mL/100g/min. Conclusion The results demonstrated as age increased, individuals reported lower symptom severity, suggesting a potential age-related decline in overt ADHD symptoms, particularly in hyperactivity and impulsivity. These findings align with developmental trajectories observed in ADHD and underscore the importance of age as a factor in symptom presentation and assessment. Future research should further explore how symptom manifestation evolves across the lifespan and how it may impact diagnosis, treatment planning, and functional outcomes.