The 18-item Swanson, Nolan and Pelham Rating Scale (SNAP-IV) assesses difficulties in attention and behavioural regulation in children and adolescents (Swanson, 1992; Swanson et al., 2012).
The 18-item Swanson, Nolan and Pelham Rating Scale (SNAP-IV) assesses difficulties in attention and behavioural regulation in young people under the age of 18 years (Swanson, 1992; Swanson et al., 2012). The items ask parents, caregivers, or teachers about a young person’s traits and behaviours based on DSM criteria for ADHD, yielding a score for two behavioural dimensions of ADHD:
The SNAP-IV was developed in 1992 as part of a lineage of scales dating back to the original SNAP in 1980. Multiple versions of varying length exist, including 90-, 43-, 30-, 26-, and 18-item versions. The 18-item version comprises the DSM-IV ADHD symptom criteria (9 Inattention items and 9 Hyperactivity/Impulsivity items), which are consistent with the DSM-5-TR ADHD symptom criteria, and is appropriate when the focus of assessment is solely on ADHD symptomatology. Longer versions that include items for other developmental and mental disorders may be preferable when a more comprehensive assessment of attention and behavioural regulation difficulties is required, such as for differential diagnosis.
It is also important to note that the SNAP-IV focuses on assessing Inattention- and Hyperactivity/Impulsivity-related deficits and/or symptom severity. In contrast, the Strengths and Weaknesses of Attention-Deficit/Hyperactivity Disorder Symptoms and Normal Behavior Scale (SWAN) (Swanson et al., 2012) assesses Inattention and Hyperactivity/Impulsivity on a continuum ranging from strengths to difficulties, providing a more balanced assessment of attention and behavioural regulation.
As the SNAP-IV is completed by an informant rather than the young person themselves, parent, caregiver, or teacher details can be added to the young person’s client file. An informant can be added by following the steps outlined in the User Guide. Obtaining ratings from different informants is recommended, as each informant observes the young person in different settings. Parent and teacher ratings often differ due to genuine variability in behaviour across settings, different frames of reference, and other factors. Such discrepancies can provide valuable clinical information about the nature of a young person’s difficulties and where they may benefit most from support.
The SNAP-IV can be used by an appropriately trained professional, such as a psychologist or paediatrician, for initial screening for ADHD before or as part of a comprehensive assessment. The SNAP-IV alone is not sufficient to establish a diagnosis.
The SNAP-IV consists of 18 items based on DSM criteria for ADHD, divided into two subscales:
Each item is rated on a 4-point scale (0 to 3), ranging from Not At All to Very Much. Subscale scores range between 0 and 27, with higher scores indicating greater symptom severity.
The scoring approach uses scoring guidelines recommended by the Canadian ADHD Resource Alliance (CADDRA) and Canadian Collaborative Mental Health Care Initiative to classify the severity of the young person’s subscale scores:
The average score for each subscale is calculated by dividing the subscale score by the number of items in the subscale. The average subscale scores are expressed as percentiles based on normative data for a community sample of school children aged 5 to 11 years (Bussing et al., 2008). These percentiles are informant-specific, derived from either parent- or teacher-rated SNAP-IV data. When the informant type is “Other” or unknown, percentiles derived from parent-rated SNAP-IV data are used. The percentiles contextualise the young person’s scores relative to the typical scores of young people in the community. Note that the percentiles may be less applicable when assessing adolescents, as the normative sample did not include young people over the age of 11 years.
The SNAP-IV can be used by an appropriately trained professional, such as a psychologist or paediatrician, for initial screening for ADHD before or as part of comprehensive assessment. The SNAP-IV alone is not sufficient to establish a diagnosis.
Although the 18-item version of the SNAP-IV has not been formally validated as a standalone measure, the modular structure of the SNAP-IV — with items directly mapping to DSM-IV ADHD symptom criteria and subscales scored independently — allows psychometric properties of the Inattention and Hyperactivity/Impulsivity subscales to be inferred from validation studies of other SNAP-IV versions that include the same items.
Bussing and colleagues (2008) examined the psychometric properties of the 26-item MTA (i.e., NIMH Multimodal Treatment Study of ADHD) version of the SNAP-IV in a community sample of school children (n = 1,613 parents; n = 1,205 teachers). Internal consistency was acceptable for both ADHD subscales: Cronbach’s alpha coefficients ranged from .88 to .89 (parent) and .95 to .96 (teacher) for Inattention, and from .76 to .80 (parent) and .91 to .92 (teacher) for Hyperactivity/Impulsivity. Hall and colleagues (2019) reported similar findings in a clinical sample of children with suspected ADHD (n = 250), with Cronbach’s alpha coefficients of .91 (parent) and .96 (teacher) for Inattention, and .86 (parent) and .93 (teacher) for Hyperactivity/Impulsivity.
Factor analytic studies consistently find an Inattention factor and Hyperactivity/Impulsivity factor in the SNAP-IV (Bussing et al., 2008; Hall et al., 2019; Swanson et al., 2012). This is consistent with the DSM-IV and DSM-5-TR conceptualisation of ADHD as a two-dimensional construct.
Interrater reliability between parent and teacher ratings is modest, with correlations of approximately .49 for Inattention and .43 for Hyperactivity/Impulsivity (Bussing et al., 2008). This level of agreement is consistent with the broader literature on parent-teacher concordance for child behaviour ratings. Such discrepancies are thought to reflect multiple factors: genuine differences in child behaviour across settings, differences in rater perceptions of developmentally normative behaviours (Amador-Campos et al., 2006), and different understandings of symptom criteria by parents and teachers (Garcia-Rosales et al., 2020). Teachers, who observe many children of similar ages, may have a broader frame of reference for judging what constitutes atypical behaviour, whereas parents tend to draw comparisons within their own family or among friends.
Research demonstrates good criterion validity for the SNAP-IV, with Inattention and Hyperactivity/Impulsivity scores showing significant associations with ADHD diagnoses derived from structured diagnostic interviews (Bussing et al., 2008; Hall et al., 2019). The SNAP-IV also demonstrates appropriate discriminant validity, with ADHD scores correlating more strongly with externalising behaviours than with internalising symptoms (Zieff et al., 2022). Across numerous clinical trials, including the MTA (Swanson et al., 2001), the SNAP-IV has been shown to be sensitive to treatment effects, demonstrating that it is useful for monitoring response to therapeutic interventions. Given its high sensitivity in identifying ADHD symptoms, the SNAP-IV is well-suited as a screening instrument and for tracking symptom change over time within a comprehensive clinical assessment framework; however, its lower specificity means it should be used as one component of a broader diagnostic evaluation rather than as a standalone diagnostic tool (Hall et al., 2019).
In the context of ADHD assessment, cutoff scores indicate whether symptom levels are clinically significant, whereas severity classifications describe the frequency and intensity of symptoms. It is important to note that different studies and scoring guides describe different cutoff scores for the SNAP-IV, often without adequate documentation of their provenance or empirical basis. For instance, the origin of the “Tentative 5% Cutoffs” could not be identified in the available literature or documentation, despite appearing in some online materials.
Cutoff scores reported in Swanson (1992) should not be applied to the SNAP-IV as they are derived from teacher ratings for the original SNAP, which was based on DSM-III domains that included Impulsivity and Hyperactivity as separate subscales. This structure is incompatible with the combined Hyperactivity/Impulsivity subscale of the SNAP-IV.
Although the severity classifications recommended by the Canadian ADHD Resource Alliance (CADDRA) and Canadian Collaborative Mental Health Care Initiative have not been validated, NovoPsych examined their correspondence with percentiles calculated using pooled means and standard deviations obtained from a study by Bussing and colleagues (2008). The Mild, Moderate, and Severe classifications align with progressively higher percentile ranges, starting at a minimum of the 80th percentile for the Mild classification, suggesting the classifications capture meaningfully distinct levels of symptom severity. In the absence of validated alternatives, this correspondence supports their clinical use.
Normative data for the SNAP-IV are based on a community sample of school children aged 5 to 11 years (Bussing et al., 2008). The pooled means and standard deviations for parent- and teacher-rated subscale scores are as follows:
These pooled means and standard deviations are used to convert the young person’s subscale scores to percentiles, providing useful information about the extent of their attention and behavioural regulation difficulties relative to young people in the community. Note that the percentiles may be less applicable when assessing adolescents, as the normative sample did not include young people over the age of 11 years.
The Swanson, Nolan and Pelham (SNAP) rating scale has undergone several revisions since its original development in 1981, evolving alongside revisions of the DSM. The original SNAP was developed to assess symptoms according to DSM-III criteria. Subsequent versions, including the SNAP-III-R and SNAP-IV, were formulated to align with the DSM-III-R and DSM-IV criteria, respectively.
Today, multiple configurations of the SNAP-IV are in circulation. The 90-item SNAP-IV includes the DSM-IV ADHD symptom criteria (9 Inattention items and 9 Hyperactivity/Impulsivity items) and ODD symptom criteria (8 items) plus screening items for a range of other conditions (e.g., conduct disorder, anxiety, mood disorders, and personality disorders), as well as the 10-item Swanson, Kotkin, Agler, Mylnn, and Pelham (SKAMP) Rating Scale measuring ADHD-related impairment in the classroom setting. The 43-item version combines DSM-IV ADHD symptom criteria (18 items) with additional symptoms from DSM-III and DSM-III-R that were not retained in DSM-IV, plus items from the Conners Index Questionnaire and IOWA Conners Questionnaire. A 30-item version has also been used in some studies. The 26-item version, which itself has a variant developed for the Multimodal Treatment Study of ADHD (MTA), comprises the 18 DSM-IV ADHD symptoms and 8 ODD symptoms. Finally, the 18-item version focuses exclusively on the DSM-IV ADHD symptoms.
James M. Swanson, the primary author of the SNAP, also developed the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior Scale (SWAN). While the SNAP-IV asks informants to rate how often a young person displays difficulties or symptoms, the SWAN reframes the same behaviours as a continuum ranging from strengths to difficulties. This produces a more normally distributed spread of scores and allows identification of relative strengths in attention and behavioural regulation.
The SNAP-IV was originally developed to align with DSM-IV ADHD symptom criteria. With the publication of DSM-5 and DSM-5-TR, clinicians may reasonably ask whether the SNAP-IV remains a valid ADHD assessment tool.
The core symptom criteria for ADHD have remained essentially unchanged from DSM-IV to DSM-5-TR. The 18 symptoms — 9 for Inattention and 9 for Hyperactivity/Impulsivity — are the same across both editions. The primary changes in DSM-5 and DSM-5-TR relate to other diagnostic requirements: the age of onset criterion was raised from 7 to 12 years, the symptom threshold for adults was reduced from 6 to 5 symptoms per domain, the exclusion criterion for Autism Spectrum Disorder was removed, and “subtypes” were renamed “presentations” to reflect their potential variability over time.
Because the SNAP-IV items directly assess the 18 core symptoms that remain unchanged, the SNAP-IV continues to be widely accepted as appropriate for assessing ADHD symptoms under current diagnostic frameworks. The SNAP-IV has been widely used in research and clinical practice for decades and continues to be considered a valid ADHD assessment tool.
Rating scales such as the SNAP-IV can be used as part of a comprehensive assessment process and are not designed to be used in isolation to establish or rule out an ADHD diagnosis. The role of rating scales is to efficiently gather structured information about the frequency and severity of specific behaviours across settings and informants, providing quantifiable data that can be compared to normative reference samples. Additionally, because the SNAP-IV items correspond directly to DSM behavioural criteria for ADHD, responses can inform clinical judgement about whether specific diagnostic criteria are met.
A comprehensive ADHD assessment typically integrates multiple sources of information, including a detailed developmental and medical history, clinical interview exploring the nature, onset, and context of presenting concerns, rating scales completed by multiple informants, consideration of alternative explanations or co-occurring conditions, and assessment of functional impact across home, school, and social settings. This allows clinicians to consider a range of possible explanations for a client’s presentation and develop an individualised understanding that informs appropriate support.
Discrepancies between parent and teacher ratings on the SNAP-IV are common and should be viewed as clinically informative rather than problematic. Research consistently shows moderate rather than high agreement between informants, and this pattern appears across ADHD rating scales more broadly. Rather than attempting to determine which informant is “correct,” clinicians should consider what the discrepancy might reveal about the young person’s presentation and needs.
Several factors may contribute to differing ratings. First, genuine situational variability: a young person may experience greater difficulty in one environment due to differences in structure, stimulation levels, social demands, or available support. For example, a highly structured classroom with clear expectations may scaffold attention more effectively than a busy home environment with multiple competing demands. Second, differing frames of reference: teachers observe many children of similar ages and may have a broader comparison group for judging what constitutes developmentally typical behaviour, whereas parents tend to draw comparisons within their own family or among friends. Third, different interpretation of symptom criteria: parents and teachers may understand or apply the behavioural descriptions differently, even when observing similar behaviours. Fourth, relationship and context factors: the relationship between the young person and each informant may influence both how the young person behaves and how their behaviours are perceived and reported.
When parent and teacher ratings on the SNAP-IV differ substantially, clinicians might explore the specific contexts in which difficulties are more or less pronounced, consider what environmental factors might explain the differences, and use this information to guide contextualised recommendations. Importantly, certain patterns of discrepancy may suggest alternative or additional diagnoses. For example, elevated difficulties reported primarily in the classroom — but not at home — may indicate a specific learning disorder rather than ADHD, as academic demands can produce behaviours that superficially resemble inattention or disengagement. Direct observation, structured interviews, and targeted assessment of other domains (such as academic skills) can help clarify the nature and context of reported difficulties. Rather than averaging or dismissing discrepant scores, the pattern of differences across informants often provides valuable clinical information about the nature of a young person’s difficulties and where they may benefit most from support.
Yes, the SNAP-IV is well-suited for monitoring changes in ADHD symptoms over time. Indeed, it was used as a primary outcome measure in the Multimodal Treatment Study of ADHD (MTA), one of the largest and most influential ADHD treatment studies conducted to date.
When using the SNAP-IV for monitoring treatment response, clinicians can administer the scale at baseline and at regular intervals during and after intervention to track changes in Inattention and Hyperactivity/Impulsivity. Because the SNAP-IV does not specify a recall period, clinicians can instruct respondents to rate the young person’s behaviour over a defined timeframe (e.g., the past week or past month) and use the same recall period at each administration to ensure comparability. Reductions in scores indicate improvement in symptom frequency and severity as perceived by the informant. Because parent and teacher perspectives may differ, it is recommended to gather ratings from both informants at each time point to understand whether improvements are generalising across settings.
Clinicians may also wish to supplement the SNAP-IV with measures of functional and other outcomes (e.g., academic performance, wellbeing, quality of life) when evaluating treatment effectiveness.
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