ADHD Clinical Outcome Scale (ACOS)

Abstract

The ADHD Clinical Outcome Scale (ACOS), developed by Adamis et al. in 2024, is a highly concise and psychometrically robust instrument designed specifically for measuring clinical outcomes in adults diagnosed with ADHD. The scale focuses on core symptomatic domains, including attention and organizational difficulties, hyperactivity and impulsivity, and crucial associated challenges such as comorbidities, substance use, self-harm tendencies, and relationship tension. ACOS is available in both clinician-administered and patient self-report versions, having undergone rigorous expert review and pilot testing to ensure its utility in routine clinical practice.

Keywords

ADHD Symptoms, Attention/Function, Comorbidities, Dysregulation, Risk-Taking Behaviours, Clinical Outcomes, Adult ADHD.

Authors

Adamis, Dimitrios; Singh, Jasmin; Coada, Iulian; Wrigley, Margo; Gavin, Blánaid; McNicholas, Fiona.

Purpose

The primary purpose of the ACOS is to provide a standardized, reliable, and efficient method for the routine measurement of clinical outcomes in adult patients attending ADHD clinics. Its design facilitates the evaluation of symptomatic severity and associated functional impairments over short timeframes.

By evaluating a comprehensive range of key symptoms and related psychosocial challenges—extending beyond the traditional core symptoms of inattention and hyperactivity/impulsivity—the ACOS allows clinicians to track therapeutic progress effectively and identify areas requiring intensive intervention, such as risk behaviors and affective dysregulation.

Construct

The psychological construct measured by the ACOS is broadly defined as ADHD Clinical Outcomes, encompassing the symptomatic burden and functional impairments experienced by adults with Attention-Deficit/Hyperactivity Disorder. This construct is multidimensional, reflecting the complex clinical presentation of ADHD in adulthood.

The ACOS operationalizes this construct through four distinct factors: Attention/Function, Dysregulation, Comorbidities, and Risk-Taking Behaviours, ensuring that the measurement captures the full spectrum of clinical impact relevant to this population.

Validity

The validity of the ACOS was established through concurrent validation methods, demonstrating its ability to correlate significantly with established measures of quality of life and functional impairment related to ADHD.

Specifically, total ACOS scores showed significant negative correlations with the Adult ADHD Quality of Life Scale (AAQoL) (r = −0.573, P < 0.001) and AAQoL psychological health scores (r = −0.547, P < 0.001). Furthermore, the ACOS demonstrated a significant positive correlation with the Weiss Functional Impairment Rating Scale (WFIRS) scores (r = 0.477, P < 0.001). These results strongly support the concurrent validity of the ACOS as a measure of increased symptomatic severity corresponding to poorer quality of life and higher functional impairment.

Reliability

The ACOS demonstrates strong psychometric reliability across multiple domains, supporting its use as a consistent clinical tool.

Internal Consistency: The scale exhibited excellent internal consistency, with a calculated Cronbach’s alpha of 0.928. This high value suggests that the items within the scale measure the underlying construct cohesively. Test-Retest Reliability: Stability over time was confirmed by an Intraclass Correlation Coefficient (ICC) of 0.829 (95% CI: 0.786–0.867, P < 0.001), indicating strong stability of scores upon repeated administration. Interrater Reliability: For the total ACOS score, the interrater reliability, measured by Pearson correlation, was high (r = 0.868, P < 0.001), confirming that different clinicians administering the scale arrive at highly consistent results.

Factor Analysis

The structure of the ACOS is organized around four empirically derived factors, which correspond to distinct clusters of clinical challenges observed in adult ADHD.

These factors are: Attention/Function (covering difficulties related to focus, organization, and procrastination); Dysregulation (focusing on emotional fluctuation, temper, and anger outbursts); Comorbidities (addressing anxiety, depression, and sleep problems); and Risk-Taking Behaviours (including substance use, self-harm, and impulsivity). This factorial structure provides a detailed clinical profile of the patient’s current status.

Instrument

Test Type: Original Inventory/Questionnaire

Format: Each item is rated on a five-point Likert scale. The clinician version uses a 0-5 severity scale (0 = No problem; 5 = Very severe problem), while the patient self-report version uses a 0-5 frequency/distress scale (0 = Not at all; 5 = Extremely).

Language Available: English (Original research location: Ireland)

Population Group: Clinical population of adults diagnosed with ADHD.

Age Group: Adulthood (18+).

Population Details: The scale was validated using respondents from adult ADHD clinics located in Ireland.

Test Methodology: The ACOS utilizes dual methodology, featuring a Clinician-Administered Scale and a Patient’s Self-Rating Scale, both assessing symptom severity and behavioral problems experienced over the past two weeks.

Authorship and Affiliation

Author ORCID Identifier: Not provided in source content.

Affiliation Email addresses: The authors are affiliated with Sligo Mental Health Services Adult ADHD Clinic, the National Clinical Programme for Adult ADHD, and the Department of Psychiatry, University College Dublin.

Correspondence Address: [email protected]

Permissions & Fee and Test Year

The ACOS was published in 2024. Information regarding specific usage fees or formal permissions beyond academic citation is not detailed in the source material. No file is currently available for direct download based on the original publication entry.

Reference’s

Adamis, D., Singh, J., Coada, I., Wrigley, M., Gavin, B., & McNicholas, F. (2024). Measuring clinical outcomes in adult ADHD clinics: Psychometrics of a new scale, the Adult ADHD Clinical Outcome Scale. BJPsych Open, 10, Article e180. https://doi.org/10.1192/bjo.2024.739

Items of the ADHD Clinical Outcome Scale (ACOS)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

ACOS Scales: Clinician and Patient Versions

These scales are designed to assess the severity of various problems, symptoms, and behaviors over the past two weeks. They include a Clinician’s Scale and a Patient’s Self-Rating Scale.

I. ACOS Clinician’s Scale

Instructions: Rate the severity of each item for the patient over the last 2 weeks based on the following scale:

• 0 = No problem

• 1 = Minor problem, but no need to be addressed clinically.

• 2 = Mild problem present, but may not need clinical action.

• 3 = Moderately severe problem, clinical action is needed.

• 4 = Severe problem

• 5 = Very severe problem

Patient Information:

• Name: _______________________________

• Date: _______________________________

• Date of Birth: _______________________________

• Medications: _________________________________________________________________________

Rating Table:

II. ACOS Patient’s Scale (Self-Rating)

Instructions: Please rate how troubled you have been by each of the following items during the PAST 2 WEEKS.

Patient Information:

• Name: _______________________________

• Date: _______________________________

• Date of Birth: _______________________________

Rating Table: