Internal Structure. Results from confirmatory factor analyses (CFA) provided evidence to support the structure of the Conners 4 scales.

• Content Scales. For Parent, Teacher, and Self-Report, after testing various models, a 6-factor model performed best (1. Inattention/Executive Dysfunction, 2. Hyperactivity, 3. Impulsivity, 4. Emotional Dysregulation, 5. Depressed Mood, 6. Anxious Thoughts). This 6-factor model had strong fit statistics (across all raters, CFI and TLI ≥ .940; SRMR ≤ .050; RMSEA ≤ .051), and had factor loadings that were all positive, statistically significant, and exceeded a minimum threshold of .32.

• Impairment & Functional Outcome Scales. For Parent and Self-Report, after testing various models, a 3-factor model performed best (1. Schoolwork, 2. Peer Interactions, 3. Family Life), while a 2-factor model performed best for Teacher (1. Schoolwork, 2. Peer Interactions). These models had adequate to strong fit statistics (across all raters, CFI and TLI ≥ .935; SRMR ≤ .061; RMSEA ≤ .094), and had factor loadings that were all positive, statistically significant, and exceeded a minimum threshold of .32.

Relation to Conceptually Related Constructs. Evidence to support the convergent validity of the Conners 4 was found, given the moderate to strong correlations between the Conners 4 and established assessments measuring related constructs.

• Conners 4 and Conners 3 (median r): Parent = .71, Teacher = .83, Self-Report = .82

• Conners 4 and BASC 3 (median |r|): Parent = .77, Teacher r = .69, Self-Report r = .76

• Conners 4 and CEFI (median |r|): Parent = .62, Teacher =.76, Self-Report = .65

• Conners 4 and WFIRS (median r): Parent = .85, Self-Report = .59

Relation to Criterion Variables. The Conners 4 demonstrated a high degree of criterion-related validity as various clinical groups had distinctly different profiles of scores.

• Meaningful differences were found between clinical groups, such that ratings of youth with ADHD yielded higher scores than ratings of both youth from the General Population (median Cohen’s d for significant differences: Parent = 1.51, Teacher = 0.87, Self-Report = 0.77) and youth with Depression or Anxiety (median Cohen’s d for significant differences: Parent = 0.88, Teacher = 0.49, Self-Report = 0.57).

• Scores on the Conners 4 were able to discern the unique symptom profiles of ADHD Inattentive, ADHD Hyperactive/Impulsive, and ADHD Combined presentations (e.g., scores on scales related to hyperactivity and impulsivity tended to be higher in the ADHD Hyperactive/Impulsive and ADHD Combined groups than the ADHD Inattentive group; median Cohen’s d for significant differences: Parent = 0.68, Teacher = 0.52, Self-Report = 0.74).

• Scores on the Conners 4 distinguished symptom profiles of groups with Depression, Generalized Anxiety Disorder, and Disruptive Disorders from the General Population. The Depressed Mood scale best distinguished youth with depression (median Cohen’s d: Parent = 1.37, Teacher = 1.62, Self-Report = 2.09), the Anxious Thoughts scale best distinguished youth with Generalized Anxiety Disorder (median Cohen’s d: Parent = 1.42, Teacher = 1.59, Self-Report = 1.05), and the DSM Oppositional Defiant Disorder Symptoms scale distinguished individuals with Disruptive Disorders (median Cohen’s d: Parent = 1.94, Teacher = 1.42, Self-Report = 1.20).

Classification Accuracy. Scores from the Conners 4 were able to correctly classify youth from the General Population and those from clinical samples into their respective groups.

• Moderate to high levels of classification accuracy were demonstrated when distinguishing between youth from the General Population and those diagnosed with ADHD (all presentations). Across all analyses, overall correct classification rates ranged from 83.9% to 88.1% for Parent, 69.3% to 74.3% for Teacher, and 68.0% to 75.4% for Self-Report.

• Moderate to high levels of classification accuracy were also observed when distinguishing between youth from the General Population and those diagnosed with Depression (Parent = 83.6%, Teacher = 79.2%, Self-Report = 73.8%), Generalized Anxiety Disorder (Parent = 76.4%, Teacher = 74.5%, Self-Report = 67.9%), and Oppositional Defiant Disorder (Parent = 82.1%, Teacher = 79.3%, Self-Report = 71.2%).