The Adult ADHD Observer-Report Scale (ASRS-O) is an 18-item informant-rated measure of ADHD symptoms for adults aged 18 years and older. It is intended to be completed by someone who currently knows the adult well, such as a partner, parent, other close relative, or friend, or by a clinician or other professional who has had regular opportunity to observe the adult over the past 6 months.

The ASRS-O was created by adapting the original 18 questions of the World Health Organisation (WHO) Adult ADHD Self-Report Scale v1.1 Symptom Checklist (Kessler et al., 2005) so that they refer to the adult being rated rather than the respondent (e.g., “How often do you…” becomes “How often does this person…”). The 18 items’ content, order, and response options are unchanged from the original scale; the observer version begins by asking for the informant’s name and relationship to the client, adds an optional “Examples/details” free-text prompt beneath each item, and ends with a single open-ended question (described in Scoring & Interpretation).

Multi-Informant Assessment of Adult ADHD

Adult ADHD assessment is strengthened by integrating information from multiple informants. Diagnostic criteria for ADHD require evidence of symptoms in two or more settings, and confirming symptoms across settings typically cannot be done accurately without input from people who have observed the individual in those settings (American Psychiatric Association, 2022). Adults may also under-report or over-report their own symptoms (Sibley et al., 2012), and self-report and informant report typically agree only moderately, which means each source captures information the other misses (Achenbach et al., 2005). Accordingly, a structured observer report contributes genuinely additional evidence rather than duplicating what the adult has already provided. Because the ASRS-O mirrors the item content of the self-report ASRS, the two measures can be administered in parallel to compare the adult’s own ratings with those of a person who observes them regularly.

ASRS-O Subscales

In addition to producing a total score, two symptom subscales assess the attentive and hyperactive-impulsive domains of adult ADHD:

• Inattentiveness, which assesses observed difficulties with sustaining attention, organisation, follow-through on tasks, memory for appointments and obligations, and distractibility.
• Hyperactivity/Impulsivity, which comprises a motor component (observable physical restlessness, including fidgeting, difficulty remaining seated, appearing driven or unable to slow down, and difficulty relaxing) and a verbal component (excessive talkativeness, finishing other people’s sentences, difficulty waiting a turn, and interrupting others).

Clinical Applications of the ASRS-O

The ASRS-O can be used by psychologists, psychiatrists, GPs, and other health professionals involved in adult ADHD care wherever an observer’s account of the adult’s behaviour would add to the clinical picture:

• Collateral information in diagnostic assessment: The measure’s primary application. Informant ratings contribute a structured account of observed behaviour to an adult ADHD assessment, alongside self-report measures and clinical interview.
• Corroborative screening and referral support: Observer ratings that reach the screening threshold strengthen the case for comprehensive assessment, and the structured report provides documentation of informant corroboration for referrers and prescribers throughout the diagnostic pathway.
• Comparing self and observer perspectives: Administered in parallel with the self-report ASRS, the matched item content allows direct comparison of the adult’s ratings with those of the observer. The two perspectives may differ in either direction, and exploring these differences — in assessment or in ongoing therapeutic work — can clarify how symptoms present across settings.

Beyond formal diagnostic assessment, the ASRS-O can also be used at therapy intake and in ongoing care, whenever a structured observer account of current behaviour would inform treatment planning or review.

The ASRS-O consists of 18 items, each rated by the informant on a five-point frequency scale ranging from Never (0) to Very Often (4). The 18 items are divided into Part A (items 1–6) and Part B (items 7–18). Higher scores reflect more frequently observed ADHD-consistent behaviours. No percentile norms are available for observer ratings. Because the ASRS-O mirrors the item content of the self-report ASRS, scores from the two measures can be compared directly when both have been administered.

ASRS-O Scoring

Results are presented as two complementary scoring approaches. Part A, Part B, and Total scores index the frequency of observed behaviours, while the subscales indicate the domain in which observed difficulties are concentrated.

Part A, Part B, and Total Score:

• Criterion (Part A): items 1–6; range 0 to 24. Consists of the six items most predictive of ADHD diagnostic status and, when used alone, constitutes the six-item ASRS Screener.
• Additional Symptoms (Part B): items 7–18; range 0 to 48. Provide additional information to support clinical interpretation beyond Part A.
• Total Score: items 1–18; range 0 to 72; overall level of observed ADHD-consistent behaviours.

The ASRS-O subscales are scored differently from the Part A, Part B, and total scores. Rather than summing the informant’s response options (0 to 4), each subscale scores symptoms dichotomously (i.e., present or absent). A symptom is counted when the informant rates the behaviour at or above its scoring threshold. For some behaviours, a rating of Sometimes or higher counts as an endorsed symptom (items 1-3, 9, 12, 16, 18); behaviours that are common in everyday life count only when rated Often or higher (items 4-8, 10, 11, 13-15, 17). The response table at the end of the report shows the level at which each item is counted; the scoring values displayed there are these dichotomous counting values (0 and 1), rather than the 0 to 4 frequency scores summed for Part A, Part B, and the Total.

ASRS-O Subscales:

• Inattentiveness (items 1–4, 7–11; range 0 to 9): observed difficulty sustaining attention, staying organised, remembering appointments, avoiding careless mistakes, and concentrating.
• Hyperactivity/Impulsivity (Motor & Verbal) (items 5, 6, 12–18; range 0 to 9): comprising a motor component (items 5, 6, 12–14), reflecting observed difficulty sitting still, staying seated, and relaxing, and a verbal component (items 15–18), reflecting observed difficulty regulating how much the person talks, interrupting others, and waiting their turn.

The subscale score is the number of symptoms counted, also expressed as a percentage of symptoms endorsed — for example, 7 of 9 symptoms on the Inattentiveness subscale is shown as 78%. This symptom-counting approach matches how the subscales are scored on the self-report ASRS.

ASRS-O Part A Interpretive Categories

The following categories apply only to the ASRS-O Part A score (items 1-6). Interpretation is based on two complementary approaches: the four interpretive categories below and a screening threshold of 14 or more for a positive observer screen. Both are derived from the validation research on the self-report ASRS Screener (Kessler et al., 2007) and reflect the current official scoring guidance (Harvard Medical School, 2024). These categories derive entirely from self-report ASRS research and have not been validated for observer ratings. They should therefore be regarded as approximate reference points for interpreting observer scores rather than as established cutoffs for informant data.

ASRS-O Interpretive Categories:

• 0 to 9: Not consistent with ADHD. The informant reports the observed behaviours occurring at a frequency well below the screening threshold.
• 10 to 13: Subthreshold. The informant reports some observed ADHD-consistent behaviours, below the level of a positive screen but potentially worth clinical attention in the context of other clinical information.
• 14 to 17: Consistent with ADHD. The informant’s ratings reach the positive screening threshold of 14 or more, indicating observed behaviours at a level that may warrant further assessment.
• 18 to 24: Highly consistent with ADHD. The informant reports observed ADHD-consistent behaviours at a high frequency across the screener items.

A score of 14 or more on Part A meets the threshold for a positive observer screen. It indicates that a person who knows the adult well has observed ADHD-consistent behaviours at a clinically notable frequency; it does not establish a diagnosis. Observer ratings provide collateral information that complements, rather than substitutes for, self-report and clinical interview, and the ASRS-O results should be integrated with the broader clinical picture.

ASRS-O Graphs

On first administration, the report presents two graphs. The first displays the Criterion (Part A) score along the 0 to 24 range, displayed against the four Part A interpretive categories and the screening threshold of 14.

The second graph presents the subscale results: the Inattentiveness and Hyperactivity/Impulsivity subscale scores as the percentage of symptoms endorsed, with the Motor and Verbal components of Hyperactivity/Impulsivity distinguished as stacked segments within the bar, alongside a bar labelled ‘Total’ summarising all 18 items on the same percentage scale (labelled ‘Total’ rather than ‘Total Score’ to distinguish it from the summed Total Score in the Results table).

On multiple administration, a line graph reports the Criterion (Part A) score across successive administrations against the same Part A interpretive categories.

Development of the ASRS-O

The basis of the ASRS-O, the ASRS v1.1 Symptom Checklist, was developed by a World Health Organization workgroup by calibrating items against blinded clinical interviews in a subsample of the United States National Comorbidity Survey Replication (Kessler et al., 2005). The 18 items operationalise the DSM-IV adult ADHD symptom criteria, and the first six items (Part A) were identified as the most predictive of diagnostic status.

The ASRS-O is an informant adaptation of that instrument. Each item is reworded into the third person. The wording implemented on NovoPsych follows an observer version that is in clinical use internationally. The observer items are direct third-person conversions of the self-report items, with one substantive difference: item 18 omits the self-report’s qualifier “when they are busy”, making the observer item slightly broader. It is important to note that the ASRS-O has not been validated as a standalone instrument. No study has established reliability, diagnostic accuracy, factor structure, or score thresholds for an observer-rated version of the ASRS. Direct evidence is limited to a single peer-reviewed study (Gray et al., 2014), in which 59 informants of college students with diagnosed ADHD completed an observer-adapted ASRS; that study examined self–informant agreement and did not evaluate the observer form’s psychometric properties. The item wording used in that study was not published, so its correspondence with the observer version in clinical circulation (the version implemented on NovoPsych) cannot be confirmed.

The remainder of this section, therefore, summarises evidence from the self-report ASRS v1.1, on which the observer version is based, together with findings from observer forms of other adult ADHD rating scales that provide context for interpreting informant ratings. Self-report-derived findings are not evidence for the observer adaptation and are presented as reference points only. ASRS-O results should accordingly be interpreted with caution. Scores provide a structured account of an informant’s observations rather than the output of a validated screening instrument, and the reference thresholds carry the provenance limitations described above.

ASRS Reliability

Internal consistency for the 18-item ASRS v1.1 Symptom Checklist is consistently strong across samples. The Swedish translation showed alpha of .91 in a young-adult psychiatric sample (N = 151; von Wallenberg Pachaly et al., 2024), and internal consistency was .95 in a large Norwegian sample combining adults with ADHD and population controls (N = 1,554; Brevik et al., 2020). Adler et al. (2006) reported a Cronbach’s alpha of .88 in adult ADHD patients (N = 60), using a pilot version of the checklist with a 1-week recall frame. For the six Screener items scored on the summed 0 to 24 metric, test-retest correlations ranged from .74 to .77 across retest intervals in a large health plan sample (Kessler et al., 2007).

ASRS Validity

Self-reported ASRS symptom ratings agree strongly with clinician-rated symptoms: in a sample of adults already diagnosed with ADHD, the intraclass correlation between the self-administered checklist and the same 18 DSM symptom items administered by a clinician was .84 for total scores (Adler et al., 2006). This represents concordance within identified cases rather than evidence that the scale agrees with clinicians about who has ADHD. The self-report ASRS discriminates well between adults with and without ADHD, with an area under the curve of .904 for the full 18-item scale and .903 for the six Part A items (Brevik et al., 2020). In a young-adult sample in which ADHD had to be distinguished from disorders with overlapping symptoms (borderline personality disorder and bipolar disorder), the ASRS retained good discrimination (AUC approximately .81; von Wallenberg Pachaly et al., 2024), supporting its usefulness in the mixed presentations typical of referred adults. No diagnostic accuracy data have been published for an observer-rated ASRS.

ASRS Factor Structure

Factor-analytic studies of the 18-item self-report ASRS support a strong general ADHD dimension with more specific symptom groupings within it. In a large psychiatric outpatient sample (N = 1,094), all 18 items loaded at .40 or above on a general ADHD factor, and the best-fitting model distinguished three specific dimensions: inattentiveness, motor hyperactivity/impulsivity, and verbal hyperactivity/impulsivity (Stanton et al., 2018). Once the general factor was accounted for, however, the specific dimensions retained only modest reliable variance (Stanton et al., 2018), and the general factor accounted for the majority of reliable variance in self-report ASRS scores (77.9% in an adolescent sample; Somma et al., 2019). This pattern supports interpreting the total score as the primary index, with the subscales providing secondary profile detail, and underpins the NovoPsych presentation of an Inattentiveness subscale and a combined Hyperactivity/Impulsivity subscale with motor and verbal components. The factor structure of observer-rated versions of the ASRS has not been examined.

ASRS-O Cross-Informant Agreement

A central psychometric question for an informant measure is how informant ratings relate to self-report. In Gray et al.’s (2014) study, informant ratings on the observer-adapted ASRS correlated moderately with students’ self-reports on the 18-item checklist (r = .46 after controlling for cognitive ability; n = 59 informant pairs). Additionally, 98% of informant forms met the original Part A criterion-box rule (four or more items rated in the shaded response categories) in this sample of adults with diagnosed ADHD. Of note, students’ self-reported total scores were modestly higher than informant totals (a difference of approximately 4 points on the 72-point scale).

Agreement Benchmarks From Other Adult ADHD Measures. The level of agreement Gray et al. (2014) found between self-report and observer forms of the ASRS is typical of informant ratings across instruments and populations. A meta-analysis of cross-informant correlations in adult psychopathology found average self-informant correlations of .43 for internalising and .44 for externalising problems when both parties completed parallel instruments (Achenbach et al., 2005). For adult ADHD specifically, self-partner agreement on the Conners’ Adult ADHD Rating Scales (CAARS), measured with intraclass correlations, ranged from .44 to .61 across symptom clusters in a clinical sample (Kooij et al., 2008), and self-informant agreement averaged .59 in a community sample of mixed informants completing the short observer form (Amador-Campos et al., 2014). The self–observer agreement observed for the ASRS therefore falls within the expected range for informant measures of adult ADHD, supporting the conclusion that the observer adaptation shows a pattern of agreement similar to informant versions of comparable scales.

Direction of Self–Informant Differences. Research has found that the direction of self–informant differences varies across populations. Adults whose ADHD was diagnosed in adulthood tend to rate their own symptoms somewhat higher than their informants do (Gray et al., 2014; Mörstedt et al., 2015), whereas young adults diagnosed with ADHD in childhood tend to under-report relative to their parents, who identify substantially more ongoing symptoms and impairment (Sibley et al., 2012). Neither direction of difference indicates that one rater is wrong; the pattern of disagreement is itself assessment information.

Combining Self and Observer Report in ADHD Assessment. No study has examined self and observer ASRS forms used jointly for screening. Evidence from another adult ADHD scale suggests that combining self- and observer-report may add value: in a clinic-referred sample completing parallel self and observer forms of the CAARS, treating only cases where both raters reported elevated symptoms as screening positive raised the proportion of positives with confirmed ADHD from 75% to 82%, compared with self-report alone (Van Voorhees et al., 2011).

ASRS-O Reference Thresholds

The reference thresholds for the ASRS-O used in NovoPsych are taken directly from the scoring research on the self-report ASRS. The self-report ASRS exists in two forms: the full 18-item ASRS v1.1 Symptom Checklist and the six-item ASRS Screener, which comprises the same six items that form Part A of the checklist. Kessler et al. (2007) evaluated summing the six Part A items on the full 0 to 4 response metric, and recommended a four-level classification of this score (0 to 9, 10 to 13, 14 to 17, and 18 to 24), with a score of 14 or more as the positive screen. This classification discriminated between adults with and without clinician-diagnosed ADHD with an area under the curve of .90. Harvard Medical School (2024) adopted this summed scoring approach and the cutpoint of 14 or more as the current official scoring guidance for the ASRS Screener, replacing the original scoring method, in which each item counted as an endorsed symptom only when rated at or above an item-specific frequency level, with four or more endorsed items constituting a positive screen. This item-count method had shown weaker performance on cross-validation (Kessler et al., 2007).

Because no observer-specific summed-score thresholds have been evaluated, NovoPsych applies the self-report ASRS score bands to the ASRS-O Part A score. These categories provide reference points for interpreting observer ratings rather than validated observer-specific cutoffs. Only one study has administered an observer-adapted ASRS (Gray et al., 2014), and it used the original item-count screening rule rather than the summed-score bands described above. In that study, 98% of informants rating adults with diagnosed ADHD met the screening criterion, providing evidence that informants readily observe and report ADHD-consistent behaviours, but not evidence for the score bands themselves.

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