Concerns With Diagnostic Overshadowing Scale (CDOS)

Abstract

The Concerns With Diagnostic Overshadowing (DO) Scale (CDOS), developed by Fahmi and Mussap (2025), is a specialized, 24-item psychological instrument designed to quantify the experiences of Diagnostic Overshadowing in both patients with a psychological condition and their carers. The scale’s development began with a comprehensive review of qualitative literature, resulting in a preliminary 37-item draft. Item refinement was informed by feedback from adults who had experienced DO, ensuring high content validity.

Subsequent psychometric evaluation utilized three international samples drawn from Australia, the United States, the United Kingdom, and Canada. Factor analyses identified a robust final three-factor structure. The scale demonstrates strong evidence of construct validity through Structural Equation Modeling, and acceptable internal consistency and test-retest reliability across its primary factors.

Keywords

Diagnostic Overshadowing, Preexisting Condition, Treatment Delay, Treatment Interference, Experiences, Concealment, Internalization, Health Care Delivery, Medical Diagnosis, Treatment Withholding, Psychometric evaluation, Lived Experience.

Authors

Fahmi, Danielle, Mussap, Alexander J.

---

Purpose

The CDOS serves as a critical measure to assess the patient and carer perspective regarding interference with medical diagnosis or treatment that is directly attributable to a patient’s pre-existing psychological or behavioral health condition. This interference, known as Diagnostic Overshadowing, often leads to delays in care and misdiagnosis of physical illnesses.

By quantifying the frequency and severity of these experiences, the CDOS provides researchers and clinicians with a standardized tool to study the negative impacts of stigma within health care delivery and to evaluate interventions aimed at improving integrated physical and mental health care.

Construct

The scale measures the construct of concerns related to experiencing Diagnostic Overshadowing (DO). This construct is empirically defined by a three-factor structure, which reflects different dimensions of the DO experience:

• CDOS-Internalized: Measures internal conflict, self-doubt, and difficulty discerning whether symptoms are physical or psychological in origin.
• CDOS-Concealment: Assesses the behaviors related to deliberately avoiding or actively hiding the pre-existing mental health diagnosis from health professionals.
• CDOS-Experienced: Captures the direct, external experiences of being dismissed, ignored, or mistreated by health care professionals due to the mental health diagnosis.

Validity

The validation process provided robust support for the scale’s psychometric properties. Structural Equation Modeling (SEM) yielded convergent evidence of construct validity by showing expected relationships with measures of health care delays and distrust. The CDOS-Experienced factor demonstrated a crucial role by fully mediating the pathways from medical delays to distrust in both health care professionals and services.

Specific path analyses results confirmed the mediating effect: βMedical delays → CDOS → Trust in professionals = −.44 (p < .001) and βMedical delays → CDOS → Trust in services = −.42 (p < .001). These findings indicate that the experience of DO explains a significant portion of the variance in patient trust (R² = .56 for professionals; R² = .54 for services). Furthermore, content validity was confirmed through expert review and feedback gathered from individuals who had lived experience of DO during the item refinement phase.

Reliability

Internal consistency was assessed using Cronbach’s alpha, showing strong reliability across all factors: CDOS Experienced (α = .95), CDOS Internalized (α = .92), and CDOS Concealment (α = .84). These values indicate high homogeneity among the items within each subscale.

Test-retest reliability, measured via Pearson bivariate correlations over a 1-year follow-up period, was acceptable for the CDOS Experienced subscale (r = .79, p < .01). However, the stability was weaker for CDOS Concealment (r = .62, p < .01) and CDOS Internalized (r = .40, p < .01), suggesting that the latter two constructs may be more temporally sensitive or subject to change over a 12-month period.

Factor Analysis

The scale structure was rigorously examined using both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA). EFA, using Principal Component Analysis (PCA) on odd-numbered cases, confirmed sampling adequacy (KMO = .89) and sphericity. Although seven components initially had eigenvalues above 1, inspection of the scree plot and subsequent parallel analysis supported a final three-component solution. These three factors, modeled in the PAF, collectively accounted for 60.81% of the total item variance.

CFA was conducted on even-numbered cases, with minor modifications applied to achieve improved model fit. Measurement invariance analysis supported both configural and metric invariance for the three-factor CDOS model across patient and carer groups. However, poor scalar invariance was observed, primarily attributed to higher baseline levels of CDOS Experienced and Concealment reported by patients compared to carers.

Instrument

Test Type: Original

Format: Inventory/Questionnaire utilizing a 5-point Likert-type scales anchored between 1 (never) and 5 (always) to indicate the frequency of DO instances.

Language Available: English

Population Group: Human (Male, Female, Transgender). Gender Identities Reported: Women, Men, Trans/Nonbinary, Other. Location: Australia, United States, United Kingdom, Canada.

Age Group: Adulthood (18 yrs & older); Young Adulthood (18-29 yrs); Thirties (30-39 yrs); Middle Age (40-64 yrs); Aged (65 yrs & older).

Population Details: The scale was developed using samples of patients diagnosed with a psychological condition and adults who reported experiencing DO, along with their associated carers, residing in Western, high-income countries.

Test Methodology: Test Validity, Construct Validity, Content Validity, Convergent Validity, Discriminant Validity, Test Reliability, Internal Consistency, Test-Retest Reliability, Factor Analysis, Confirmatory Factor Analysis, Exploratory Factor Analysis, Principal Component Analysis, Measurement Invariance, Structural Equation Modeling. Administration Method: Electronic.

Keywords

Diagnostic Overshadowing, Health Care Distrust, Mental Health Stigma, Structural Equation Modeling, Patient Experience, Carer Experience, Psychological Condition, Health Disparities, Psychometrics, Internal Consistency.

---

Authors

Author ORCID Identifier: Mussap, Alexander J.: http://orcid.org/0000-0003-1290-3680

Affiliation Email addresses: Mussap, Alexander J.: [email protected]

Correspondence Address: Mussap, Alexander J.: Deakin University, School of Psychology, 221 Burwood Highway, Melbourne, Victoria, Australia, 3125, [email protected]

Permissions & Fee and Test Year

Permissions: May use for Research/Teaching

Fee: No

Test Year: 2025

Reference’s

Fahmi, D., & Mussap, A. J. (2025). Development and preliminary investigation of the Concerns With Diagnostic Overshadowing Scale (CDOS). Stigma and Health. Advance online publication. https://doi.org/10.1037/sah0000614

---

Items of the Concerns With Diagnostic Overshadowing Scale (CDOS)

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

Concerns with Diagnostic Overshadowing Scale (CDOS)

Instructions: Diagnostic overshadowing occurs when symptoms of a physical illness are dismissed, downplayed, misattributed, or misdiagnosed because of a pre-existing mental health or behavioural health condition (e.g., psychological disorder, neurodevelopmental disorder/delay, cognitive impairment, intellectual disability) that has been professionally diagnosed.

The following statements describe examples of diagnostic overshadowing, including potential self-doubts, concerns about treatment by healthcare professionals, and experiences regarding actual treatment.

Please think about the most prominent example of diagnostic overshadowing you have experienced. If you have more than one diagnosed mental health condition, focus on the one you feel had the greatest impact on your treatment. If diagnostic overshadowing occurred with more than one physical illness, focus on the physical illness most affected. The severity of the physical illness is less important than the fact it occurred after your mental health diagnosis.

Indicate how often each statement applied to you at that time using the scale below. Participation is optional.

Participant Information

Name or description of the diagnosed mental health condition:

---

Age when you received this diagnosis (in years): __________

Therapies (including medications) received (optional):

---

---

Name or description of physical illness:

---

Age when you first experienced symptoms of this physical illness (in years): __________

The physical illness was diagnosed or treated by (select all that apply):

[ ] General practitioner (doctor, physician, etc)

[ ] Specialist (paediatrician, pathologist, surgeon, etc)

[ ] Allied health professional (nurse, paramedic, etc)

[ ] Other: _________________________________________

Scale Items

Please use the following scale to provide your responses:

1 = Never

2 = Rarely

3 = Sometimes

4 = Often

5 = Always

1. I could not tell whether my symptoms were due to a physical illness or my pre-existing mental health condition. _____

2. I worried that it was my mental illness that was making me physically unwell. _____

3. I had difficulty separating my physical symptoms from my mental health condition. _____

4. I believed that my symptoms were a combination of physical illness and mental illness. _____

5. I avoided mentioning my previous mental health issues to medical practitioners. _____

6. I tried to keep my mental health diagnosis a secret from health professionals. _____

7. I avoided telling doctors that I had previously been treated for a psychological condition. _____

8. I worried that medical staff would not focus on my physical illness. _____

9. Medical staff told me that I was physically OK when I knew that I was not. _____

10. Health professionals seemed to be preoccupied with my pre-existing mental health condition. _____

11. My requests for medical intervention were ignored or dismissed. _____

12. Health professionals did not take my symptoms seriously. _____

13. I did not receive adequate help in managing my physical illness. _____

14. My physical health was ignored by medical practitioners. _____

15. Medical staff diagnosed my symptoms as signs of an underlying mental health condition. _____

16. The doctors did not believe my symptoms were real. _____

17. I was made to feel that the symptoms I experienced were somehow my own fault. _____

18. I felt that I had been labelled as ‘mentally ill’ by medical staff. _____

19. I felt that my independence was compromised by the medical system. _____

20. I felt helpless when it came to my health care. _____

21. There seemed to be a disconnect between the physical health care system and the mental health care system. _____

22. I felt misunderstood by health care professionals. _____

23. I believe that my physical health needs were not met because of my mental health diagnosis. _____

24. The health system did not treat me with respect. _____

Scoring

CDOS-Internalised = mean of items 1-4

CDOS-Concealment = mean of items 5-7

CDOS-Experienced = mean of items 8-24

Note: Despite adequate reliability, the concealment subscale (CDOS-Concealment) does not demonstrate close associations with help-seeking behaviours that should be relevant to diagnostic overshadowing concerns, such as personal delays in seeking healthcare, and trust in healthcare professionals and services. Until this matter is resolved, researchers and clinicians using the CDOS may wish to omit this subscale from their own research or practice.