Symptom epidemiology, demographic correlates, and differentiation between cognitive disengagement syndrome symptoms and ADHD symptoms in a large nonprobability sample of Iranian adolescents and adults

BACKGROUND: Cognitive disengagement syndrome (CDS) is an emerging cognitive-attentional construct characterized by excessive daydreaming, mental slowness, drowsiness, and reduced engagement with external demands. Although CDS symptoms are substantially associated with attention-deficit/hyperactivity disorder (ADHD) symptoms, accumulating psychometric and external-validity evidence supports their conceptualization as related yet distinguishable symptom dimensions. However, large-scale evidence regarding the distribution and demographic correlates of elevated CDS symptoms, as well as their differentiation from ADHD symptoms, remains limited, particularly in non-Western contexts. METHODS: In this large-scale cross-sectional study, 8,075 Iranian participants aged 15-55 years, recruited through convenience and snowball sampling, completed the Persian Adult Concentration Inventory as a self-report measure of CDS symptoms. A subsample of 2,012 participants also completed the Adult ADHD Self-Report Scale. The study examined the distribution and demographic correlates of elevated CDS symptoms and the extent to which CDS and ADHD symptom dimensions showed overlap and differentiation. Sample-based percentile thresholds were used to identify elevated symptom levels. Analyses included descriptive statistics, logistic regression, correlation and overlap analyses, discriminant function analysis, and leave-one-out cross-validation. RESULTS: Using the sample-based 95th-percentile threshold, 5.8% of participants exceeded the threshold for elevated CDS symptoms, while 11.3% exceeded the 90th-percentile threshold. Females and younger participants were more likely to exceed the elevated-symptom threshold. CDS and ADHD symptom scores were strongly correlated (r = .69), indicating substantial overlap, although differences were observed across their symptom dimensions. An exploratory discriminant function analysis yielded an original classification accuracy of 95.3% and a leave-one-out cross-validated accuracy of 93.9%; however, these findings reflect within-sample differentiation based on the current self-report measurement framework rather than diagnostic separation. CONCLUSION: In this large nonprobability Iranian sample, elevated CDS symptoms showed age- and sex-related differences. CDS and ADHD symptom dimensions demonstrated substantial overlap while also showing meaningful differences in their symptom profiles within the present self-report measurement framework. Because the thresholds were sample-based and no clinical diagnostic interviews or assessments of functional impairment were conducted, the reported percentages should not be interpreted as estimates of clinical or population prevalence, and the classification findings should not be considered evidence of diagnostic separation. These findings extend cross-cultural knowledge of CDS symptomatology and highlight the need for future representative, longitudinal, and multimethod research.