The study, led by Karim Abdolmohamadi of Azarbaijan Shahid Madani University with colleagues including Serge Brand, Asgar Alimohamadi, and Dena Sadeghi-Bahmani, recruited 8,075 valid participants aged 15 to 55 through convenience and snowball sampling in Tehran, Tabriz, Mashhad, and Isfahan between 2021 and 2024. Roughly 30 percent of questionnaires were collected in person in schools, universities, workplaces, and public centers, while 70 percent arrived through a secure online survey platform. The sample skewed heavily female, at 70.8 percent, and young, with a mean age of 24.8 years. Participants with self-reported histories of major psychiatric disorder were excluded, and incomplete, careless, or inconsistent responses were removed during screening. Crucially, the authors stress that this was a large nonprobability sample, not a nationally representative one.

Symptoms were measured with the Persian version of the Adult Concentration Inventory, a 16-item self-report scale developed by Stephen Becker and colleagues that probes three dimensions: attention problems, sluggishness, and imagination or mind-wandering. Each item is rated from zero, not at all true, to three, very true, yielding total scores from 0 to 48. The Persian version previously showed solid psychometric credentials, with a confirmed three-factor structure, fit indices such as RMSEA of 0.050 and CFI of 0.95, and a total-score Cronbach’s alpha of 0.864. In the new sample the instrument performed even better, with an alpha of 0.91 and subscale reliabilities between 0.74 and 0.86, and the score distributions were approximately normal. The mean total CDS score was 17.10 with a standard deviation of 9.45.

Because no clinically validated diagnostic cutoffs exist for the Persian inventory, the researchers used sample-based percentile thresholds. Under the conservative 95th-percentile criterion, 5.8 percent of participants, roughly one in seventeen, exceeded the threshold for elevated CDS symptoms. A slightly looser threshold of the mean plus 1.5 standard deviations flagged 8.3 percent, while the 90th-percentile cutoff captured 11.3 percent. The authors are careful to frame these figures as descriptive indicators of elevated self-reported symptoms within this particular sample, not as estimates of clinical or population prevalence. Even so, the numbers fall comfortably within the roughly 2 to 10 percent range reported in community-based studies from the United States and Europe, suggesting meaningful cross-cultural similarity in how often these symptoms appear at high levels.

The demographic patterns were striking. Females exceeded the 95th-percentile threshold more often than males, at 6.4 percent versus 4.3 percent, and the odds of elevated symptoms fell sharply with age. Adolescents aged 15 to 17 showed the highest rate at 9.1 percent, while adults aged 35 to 55 hovered near 1 to 2 percent. In a binary logistic regression, female sex carried an odds ratio of 1.46, meaning 46 percent higher odds of crossing the threshold, and each additional year of age reduced the odds by about 6 percent. The model was statistically significant but explained a modest 9.2 percent of the variance, a reminder that age and sex are correlates rather than causes. The female predominance echoes earlier findings from Turkey and South Korea, and the age gradient fits developmental perspectives suggesting that attentional control and self-regulation are still maturing through adolescence, although the cross-sectional design cannot show whether symptoms decline within individuals over time.

The second phase of the study tackled the central scientific question: is CDS merely ADHD in disguise? A subsample of 2,012 participants also completed the Adult ADHD Self-Report Scale, an 18-item World Health Organization screening instrument covering inattention and hyperactivity/impulsivity. Comparisons showed the subsample was essentially interchangeable with the rest of the cohort on CDS scores and sex distribution, with only a negligible age difference. The correlation between total CDS and total ADHD scores was strong, r = .69, indicating that the two constructs share substantial variance at the level of self-reported symptoms. The association was tightest between CDS attention problems and ADHD inattention, at r = .67, but considerably weaker between CDS dimensions and ADHD hyperactivity/impulsivity, at r = .46. Strong, in other words, but nowhere near redundant.

Overlap analysis made the partial separation concrete. Using 90th-percentile cutoffs for both scales, the researchers classified participants into four groups. A majority, 84.5 percent, exceeded neither threshold. But 5.2 percent showed elevated CDS symptoms only, 5.3 percent showed elevated ADHD symptoms only, and 4.9 percent exceeded both. Elevated symptoms in each domain therefore occurred separately almost as often as they co-occurred, mirroring earlier United States findings in which roughly 2.6 percent of children displayed elevated CDS without ADHD, 4.5 percent the reverse, and 2.4 percent both. Separation at the symptom level is not proof of diagnostic independence, the authors caution, but it consistently challenges the idea that CDS is simply a subtype of ADHD.

To probe the structure of that separation, the team ran an exploratory discriminant function analysis on participants who exceeded one threshold but not the other, using CDS subscale scores, age, and sex as predictors. The function was highly significant, Wilks’ Lambda = 0.374, and the profile differences were theoretically coherent: the CDS-only group scored relatively higher on slowness and imagination or mind-wandering, while the ADHD-only group was distinguished mainly by attention-related difficulties, with age and sex contributing little. Classification accuracy reached 95.3 percent in the original analysis and held at 93.9 percent under leave-one-out cross-validation, a technique in which each case is classified using functions built from all remaining cases to reduce optimistic bias. The authors are emphatic, however, that because the groups and predictors came from the same self-report measures, these figures reflect within-sample symptom-profile differentiation, not diagnostic accuracy or evidence of diagnostic separation.

The broader context gives these findings weight. Prior research links persistent CDS symptoms to depression, anxiety, social withdrawal, sleep problems, and academic underachievement across settings as varied as Iran, Turkey, South Korea, and the United States, while ADHD symptoms align more with executive-function deficits, impulsivity, and externalizing behavior. Preliminary neuroscientific work, including resting-state functional connectivity and magnetoencephalography studies, hints at altered vigilance-related brain systems, but no specific cognitive or neural mechanism has been established, and the present study, being purely questionnaire-based, tested none. The authors also acknowledge the limits of their design: a cross-sectional snapshot, nonprobability sampling dominated by young women, self-reported psychiatric history without clinical interviews, percentile cutoffs rather than validated diagnostic criteria, and shared-method variance across all measures. No behavioral tasks, physiological indices, or neuroimaging were included.

What the study delivers, nonetheless, is the kind of evidence the field has lacked. A systematic review found that fewer than ten of more than seventy published CDS studies used epidemiological designs, and most came from the United States or Europe. Demonstrating that elevated CDS symptoms show similar frequency ranges, the same female and adolescent skew, and the same pattern of partial overlap with ADHD in a large Middle Eastern sample extends the construct’s cross-cultural footprint. The researchers call for representative, longitudinal, and multimethod studies that combine clinical interviews, impairment measures, cognitive testing, and neurobiological tools. Until then, cognitive disengagement syndrome remains best understood not as a formal diagnosis, nor as a mere shadow of ADHD, but as a closely related yet partially distinguishable cognitive-attentional profile, one that appears to follow young women into daydreams at measurably higher rates and that psychiatry is only beginning to map.

Subject of Research: Epidemiology of cognitive disengagement syndrome symptoms and their differentiation from ADHD symptoms in Iranian adolescents and adults

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

Article References: Abdolmohamadi, K., Brand, S., Alimohamadi, A., & Sadeghi-Bahmani, D. (2026). Symptom epidemiology, demographic correlates, and differentiation between cognitive disengagement syndrome symptoms and ADHD symptoms in a large nonprobability sample of Iranian adolescents and adults. BMC Psychiatry, 26(1), Article 705. https://doi.org/10.1186/s12888-026-08346-w

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08346-w

Keywords: cognitive disengagement syndrome, ADHD, sluggish cognitive tempo, daydreaming, Iran, mental slowness, attention, symptom epidemiology, self-report, adolescents, adults, BMC Psychiatry