STRUCTURE AND VALIDITY OF ADHD IN ADOLESCENCE 3

Supplemental Table 1. Items/Symptoms from the SNAP-IV rating scale, self-report form

ADHD-IA
Item 1 / Failed to give close attention to details or made careless mistakes in schoolwork, work, or other activities
Item 2 / Had difficulty sustaining attention in tasks or play activities
Item 3 / Did not seem to listen to what was being said to you
Item 4 / Did not follow through on instructions and failed to finish schoolwork, chores, or duties in the workplace
Item 5 / Had difficulty organizing tasks and activities
Item 6 / Avoided, expressed reluctance about, or had difficulties engaging in tasks that required sustained mental effort
Item 7 / Lost things necessary for tasks or activities (e.g., school assignments, pencils, books, tools or toys)
Item 8 / Were easily distracted by extraneous stimuli
Item 9 / Were forgetful in daily activities
ADHD-HY
Item 10 / Fidgeted with your hands or feet or squirmed in your seat
Item 11 / Left seat in classroom or in other situations in which remaining seated was expected
Item 12 / Ran about or climbed excessively in situations where it was inappropriate
Item 13 / Had difficulty playing or engaging in leisure activities quietly
Item 14 / Were always "on the go" or acted as if "driven by a motor"
Item 15 / Talked excessively
ADHD-IM
Item 16 / Blurted out answers to questions before the questions had been completed
Item 17 / Had difficulty waiting in lines or awaiting turn in games or group situations
Item 18 / Interrupted or intruded on others (e.g., butted into other's conversations or games)

Note: Item content remains consistent across parent and teacher version, though the wording changes to account for rater’s relationship to adolescent.

Supplemental Table 2. Means and standard deviations for adolescent, parent, and teacher reports of the 18 ADHD symptoms from the SNAP-IV rating scale

Adolescent
M (SD) / Parent
M (SD) / Teacher
M (SD)
ADHD-IA Symptoms
Item 1 / 0.87 (0.74) / 1.23 (0.91) / 1.24 (0.84)
Item 2 / 0.62 (0.74) / 0.92 (0.92) / 1.22 (1.00)
Item 3 / 0.72 (0.76) / 1.08 (0.88) / 0.94 (0.92)
Item 4 / 0.74 (0.75) / 1.21 (1.00) / 1.15 (1.01)
Item 5 / 0.63 (0.78) / 1.22 (1.03) / 1.08 (0.96)
Item 6 / 0.65 (0.80) / 1.14 (1.04) / 1.15 (1.07)
Item 7 / 0.64 (0.82) / 0.98 (0.94) / 0.72 (0.92)
Item 8 / 0.70 (0.83) / 1.21 (0.99) / 1.34 (1.03)
Item 9 / 0.65 (0.77) / 0.96 (0.93) / 0.84 (0.88)
ADHD-HY Symptoms
Item 10 / 0.82 (0.95) / 0.67 (0.87) / 0.56 (0.86)
Item 11 / 0.38 (0.73) / 0.48 (0.78) / 0.41 (0.79)
Item 12 / 0.22 (0.56) / 0.31 (0.64) / 0.24 (0.60)
Item 13 / 0.31 (0.62) / 0.35 (0.62) / 0.44 (0.76)
Item 14 / 0.59 (0.87) / 0.50 (0.78) / 0.48 (0.82)
Item 15 / 0.84 (0.94) / 0.67 (0.95) / 0.73 (0.99)
ADHD-IM Symptoms
Item 16 / 0.57 (0.81) / 0.61 (0.88) / 0.47 (0.83)
Item 17 / 0.48 (0.78) / 0.48 (0.76) / 0.36 (0.73)
Item 18 / 0.52 (0.66) / 0.77 (0.91) / 0.57 (0.86)

Note: M = mean; SD = standard deviation.

Supplemental Table 3. Standardized symptom-factor loadings (standard errors) from the one-factor model of ADHD

Adolescent-Informant / Parent-Informant / Teacher-Informant
General ADHD / Standardized Loading (SE) / Standardized Loading (SE) / Standardized Loading (SE)
Item 1 / .60 (.05) / .76 (.03) / .70 (.05)
Item 2 / .72 (.03) / .79 (.03) / .84 (.03)
Item 3 / .69 (.04) / .77 (.03) / .75 (.04)
Item 4 / .68 (.04) / .82 (.03) / .77 (.05)
Item 5 / .69 (.04) / .76 (.03) / .79 (.04)
Item 6 / .66 (.04) / .78 (.03) / .78 (.04)
Item 7 / .56 (.05) / .80 (.03) / .73 (.04)
Item 8 / .67 (.05) / .84 (.02) / .83 (.02)
Item 9 / .63 (.05) / .82 (.02) / .76 (.05)
Item 10 / .63 (.04) / .65 (.04) / .71 (.04)
Item 11 / .61 (.06) / .73 (.03) / .72 (.05)
Item 12 / .61 (.06) / .67 (.04) / .62 (.07)
Item 13 / .64 (.05) / .60 (.05) / .72 (.05)
Item 14 / .52 (.06) / .58 (.05) / .65 (.07)
Item 15 / .50 (.06) / .58 (.05) / .75 (.06)
Item 16 / .57 (.06) / .71 (.04) / .65 (.07)
Item 17 / .62 (.05) / .67 (.04) / .71 (.07)
Item 18 / .41 (.06) / .67 (.04) / .77 (.06)

Note: All loading are significant at p < .05 unless otherwise demarcated by ns

Supplemental Table 4. Standardized symptom-factor loadings (standard errors) from the nonhierarchical two-factor model of ADHD

Adolescent-Informant / Parent-Informant / Teacher-Informant
ADHD-Inattention (ADHD-IA) / Standardized Loading (SE) / Standardized Loading (SE) / Standardized Loading (SE)
Item 1 / .62 (.05) / .81 (.03) / .80 (.03)
Item 2 / .74 (.03) / .80 (.03) / .88 (.02)
Item 3 / .73 (.03) / .76 (.03) / .82 (.03)
Item 4 / .73 (.03) / .86 (.02) / .86 (.02)
Item 5 / .74 (.03) / .83 (.02) / .88 (.02)
Item 6 / .69 (.04) / .81 (.03) / .83 (.02)
Item 7 / .56 (.05) / .82 (.02) / .73 (.04)
Item 8 / .69 (.05) / .83 (.02) / .81 (.03)
Item 9 / .65 (.05) / .85 (.02) / .82 (.03)
ADHD-Hyperactivity/Impulsivity
(ADHD-HY/IM)
Item 10 / .63 (.04) / .63 (.05) / .69 (.05)
Item 11 / .68 (.06) / .77 (.04) / .80 (.04)
Item 12 / .70 (.06) / .76 (.04) / .76 (.04)
Item 13 / .75 (.05) / .73 (.04) / .81 (.04)
Item 14 / .60 (.05) / .70 (.04) / .79 (.04)
Item 15 / .53 (.06) / .74 (.04) / .87 (.02)
Item 16 / .66 (.06) / .84 (.02) / .80 (.04)
Item 17 / .69 (.04) / .78 (.03) / .85 (.03)
Item 18 / .44 (.07) / .80 (.03) / .88 (.03)
Correlations
ADHD-IA with
ADHD-HY/IM / .73 (.05) / .72 (.03) / .65 (.04)

Note: All loading are significant at p < .05 unless otherwise demarcated by ns