ADHD & Autism — Connectedness and Overlap Scale (ACOS)
Differentiates ADHD and autism symptoms in adults with suspected overlap.
Last reviewed: May 2026
The ACOS was developed by Leitner (2014) to address a gap in clinical assessment: distinguishing overlapping features of ADHD and autism in adults. With 30–80% co-occurrence rates reported in clinical samples, many symptoms (executive dysfunction, sensory sensitivity, social difficulties) could be attributed to either condition.
Scoring & Interpretation
Each item scored on a Likert scale. Three subscale scores: ADHD-specific, Autism-specific, and Shared features. Higher subscale scores indicate greater endorsement of that trait cluster. Compare subscale profiles to understand whether the presentation is predominantly ADHD, predominantly autistic, or a genuine co-occurrence.
| Score Range | Severity | Clinical Action |
|---|---|---|
| ADHD subscale elevated | ADHD-predominant | Proceed with ADHD-focused assessment (ASRS, DIVA) |
| Autism subscale elevated | Autism-predominant | Proceed with autism-focused assessment (RAADS-R, ADOS-2) |
| Both subscales elevated | Co-occurring pattern | Dual assessment pathway — evaluate both conditions |
| Shared subscale dominant | Overlapping features | Clarify with structured interviews for both conditions |
Internal consistency: α = 0.82–0.89 across subscales (Leitner, 2014). Discriminant validity: correctly classified 78% of participants into ADHD-only, autism-only, and co-occurring groups. Convergent validity with ASRS (r = 0.71) and AQ (r = 0.68).
When to Use This vs Alternatives
Use ASRS when…
You only need to screen for ADHD symptoms and autism is not a question. The ASRS is ADHD-specific — it cannot distinguish ADHD features from autistic features that look similar.
View ASRS →Use AQ-10 when…
You only need a quick autism screen. The AQ-10 flags autistic traits but cannot tell you whether those traits are better explained by ADHD. Use ACOS when both conditions are in play.
View AQ-10 →Use WFIRS-S when…
You've established it's ADHD (not autism) and need to measure functional impairment. The WFIRS-S is for impairment quantification; the ACOS is for differential clarification.
View WFIRS-S →See It in Action
- 1Total score with severity band
- 2Individual question responses with scoring badges
- 3Clinical note on symptom frequency
- 4One-click PDF export and email delivery
What It Measures
The ACOS was developed by Leitner (2014) to address a gap in clinical assessment: distinguishing overlapping features of ADHD and autism in adults. With 30–80% co-occurrence rates reported in clinical samples, many symptoms (executive dysfunction, sensory sensitivity, social difficulties) could be attributed to either condition. The ACOS self-report measures traits across three subscales: ADHD-specific, Autism-specific, and Shared/Overlapping features.
When to Use the ACOS
Use the ACOS when a patient screens positive for ADHD AND shows autistic traits (or vice versa). It helps determine whether symptoms are better explained by ADHD alone, autism alone, or both conditions co-occurring. Particularly useful when existing screening tools (ASRS, AQ-10) both flag positive and you need to understand the overlap before deciding on comprehensive assessment.
Who It's For
Adults aged 18+. Self-report. Designed for clinical populations where ADHD and autism co-occurrence is suspected. Particularly useful in late-diagnosis presentations where masking may obscure one condition. Clinician-report version (ACOS-Clinician) also available for third-party observations.
Frequently Asked Questions
What is the ACOS (ADHD & Autism Overlap Scale)?
The ACOS is a self-report questionnaire that helps clinicians differentiate between ADHD symptoms, autistic traits, and shared features in adults. It has three subscales: ADHD-specific, Autism-specific, and Shared/Overlapping. This helps determine whether a patient has ADHD, autism, or both co-occurring.
When should I use the ACOS instead of separate ADHD and autism screeners?
Use the ACOS when a patient screens positive on both ADHD (e.g., ASRS) and autism (e.g., AQ-10) measures, or when symptoms could plausibly be attributed to either condition. The ACOS clarifies the overlap rather than forcing a binary ADHD-or-autism decision.
Can ADHD and autism co-occur?
Yes. Since DSM-5 (2013), ADHD and autism can be formally co-diagnosed. Research suggests 30–80% of autistic individuals also meet criteria for ADHD, and 20–50% of those with ADHD show significant autistic traits. The ACOS was designed specifically to assess this overlap.
Use the ACOS in your practice
Available on the Starter plan. Instant scoring, severity bands, and PDF reports included. Patients complete it on their phone or computer. Scored the moment they hit submit.