SNAP-IV: what an ADHD symptom checklist can and cannot tell you
SNAP-IV is a symptom checklist for ADHD built straight out of the DSM-IV criteria. James Swanson, Mary Nolan and William Pelham wrote the original SNAP as a 90-item rating form in 1983; later revisions cut it down to a workable length, and the 18-item version is the one schools and clinics actually use.
Those 18 items split evenly. Nine cover inattention, nine cover hyperactivity and impulsivity, matching the two DSM symptom domains. Each item is rated 0 to 3 (not at all, just a little, quite a bit, very much), so a subscale can reach 27.
One thing to know before you start: the published SNAP-IV is an informant form. Parents and teachers fill it in about a child. Here you answer about yourself, so read your result as the symptoms you notice in yourself, not as a parent or teacher rating. That distinction matters when you get to the cutoffs below.
How the scoring works
Official scoring uses the average per item, not the raw total. Add the nine inattention items and divide by nine; do the same for the nine hyperactivity items. Each average falls between 0 and 3.
The published 5% cutoffs are different for the two kinds of informant, and the gap between them is not small:
| Subscale | Teacher cutoff | Parent cutoff |
|---|---|---|
| Inattention | 2.56 | 1.78 |
| Hyperactivity/Impulsivity | 1.78 | 1.44 |
| Combined (18 items) | 2.00 | 1.67 |
An average at or above the cutoff means the rating falls in the top 5% of that informant group. For raw totals there is also a rough severity ladder, the same for both ADHD subscales: under 13 is not clinically significant, 13 to 17 mild, 18 to 22 moderate, 23 to 27 severe. These bands come from university scoring guides, not from the original scale, and they are descriptive rather than diagnostic.
What the psychometrics look like
The largest published check on SNAP-IV comes from Bussing and colleagues in 2008, using a random school-district sample in Florida: 1,613 parents and 1,205 teachers. Internal consistency was high in both, and the teacher version was tighter:
| Informant | Overall alpha | Inattention | Hyperactivity | ODD |
|---|---|---|---|---|
| Parent | .94 | .90 | .79 | .89 |
| Teacher | .97 | .96 | .92 | .96 |
Parent and teacher agreement was moderate, not high: inattention r = .49, hyperactivity r = .43, ODD r = .47, all with p under .001. A three-factor structure fitted better than four. How well the scores sort children with and without ADHD concern varied a lot by informant: parent inattention .85 and parent hyperactivity .80 on ROC AUC, teacher inattention .74 and teacher hyperactivity .71. Against an actual DISC-IV diagnosis only the parent ratings held up (.72 and .76), which is the study's own conclusion: SNAP-IV works as a screen, not as a stand-alone diagnosis.
One more finding worth knowing if you are reading scores for a boy: across all six subscales boys scored higher than girls (d = 0.29 to 0.49), and teachers rated African American children higher than Caucasian children (d = 0.49 to 0.56). Rating scales pick up who is doing the noticing as much as who has symptoms.
Where the 26-item version fits
Because oppositional behaviour so often travels with ADHD, the MTA version of the scale adds 8 ODD items (items 19 to 26), and a full 90-item research version exists with Conners and SKAMP blocks. The extra ODD subscale has its own cutoffs (1.38 teacher, 1.88 parent) and its own severity ladder: under 8, 8 to 13, 14 to 18, 19 to 24.
What this score is not
A high average here is a signal, not a verdict. ADHD diagnosis depends on when symptoms started, whether they show up in more than one setting, and how much they interfere with daily life. A questionnaire cannot establish any of that on its own. If the pattern is costing you work, study or relationships, that is worth taking to a clinician who can look at the whole picture. This page is not a diagnosis and does not replace one.