<p>Earlier research showed that a cognitive disengagement syndrome (CDS)-only group was higher on anxiety, depression, somatization, sleep difficulties, and social impairment than ADHD-inattention presentation (INP), ADHD-hyperactive/impulsive presentation (HIP), and ADHD-combined presentation (CP) groups <i>within childhood</i>, whereas the four groups were more similar on these measures <i>within adolescence</i>. Our expectation was thus that CDS-only, ADHD-INP-only, ADHD-HIP-only, and ADHD-CP-only groups would show similar levels of anxiety, depression, somatization, sleep difficulties, and impairment <i>within adulthood</i>. A nationally representative sample of Spanish adults (<i>N</i> = 4,003; ages 18 to 59; 51.1% female) was used to create: (1) control (<i>n</i> = 3,662, 91.48%); (2) CDS-only (<i>n</i> = 70, 1.75%) ; (3) ADHD-INP-only (<i>n</i> = 44, 1.10%); (4) ADHD-HIP-only (<i>n</i> = 82, 2.05%); (5) ADHD-CP-only (<i>n</i> = 42, 1.05%); (6) CDS+ADHD-INP (<i>n</i> = 37, 0.92%); (7) CDS+ADHD-HIP (<i>n</i> = 15, 0.37%); and (8) CDS+ADHD-CP (<i>n</i> = 51, 1.27%) groups. 40% of the CDS group did not qualify for the ADHD group, whereas 62% of the ADHD group did not qualify for the CDS group. Although the CDS-only, ADHD-INP-only, ADHD-HIP-only, and ADHD-CP-only groups were higher than the control group on anxiety, depression, somatization, daytime sleep-related impairment, nighttime sleep disturbance, and functional impairment, the four clinical groups were similar on the six measures. In the largest study examining CDS in adults, CDS and ADHD showed similar levels of independence for adults as found for youth. And, more importantly, CDS was as impairing as ADHD for adults within the context of the measures examined in this study.</p>