Psychometric properties of the Swedish version of the SNAP-IV rating scale parent form in a birth cohort of 11-year-old children.

A three-factor bifactor S-1 model of the Swedish SNAP-IV where all items load onto a general hyperactivity/impulsiveness factor and items specific to inattentiveness and Oppositional Defiant Disorder (ODD) load onto independent factors fit best and exhibited high internal consistency. Excluding ODD items, a similar two-factor bifactor S-1 model fit well. The SNAP-IV demonstrated robust clinical utility for identifying children diagnosed with ADHD as evidenced by significant associations between clinical diagnoses and the SNAP-IV subscales, as well as excellent classification accuracy for both the inattention and hyperactivity/impulsivity subscales when using continuous values. Taken together, the Swedish version of the SNAP-IV parent form was found to be a useful instrument with good criterion validity for assessing ADHD symptoms in 11-year-old children. The clinical application of cutoffs is discussed.