Understanding Comorbidities and Differential Diagnoses in ADD/ADHD Testing and Assessment

Why an ADD/ADHD Comprehensive Evaluation Matters

When assessing for Attention-Deficit/Hyperactivity Disorder (ADD/ADHD), it’s not just about confirming or ruling out a single diagnosis. Research shows that approximately 80% of individuals diagnosed with ADD/ADHD have at least one comorbid condition—meaning they experience another psychological disorder alongside ADHD. This overlap can significantly impact functioning, treatment, and long-term outcomes.

At Calvert + Associates, we take a thorough and structured approach to identifying both comorbidities and differential diagnoses, ensuring that each client receives an accurate understanding of their cognitive and emotional profile.

Comorbidities and Differential Diagnoses: The Basics

What Are Comorbidities in ADD/ADHD?

Comorbidities refer to additional disorders or conditions that occur alongside ADHD. These are not mere symptoms—they are diagnosable conditions that often interact with ADHD and can complicate or mask its presentation.

Identifying comorbidities is essential for developing a personalized treatment plan that addresses the full scope of an individual’s experience—not just ADHD symptoms in isolation.

Common Comorbidities with ADD/ADHD include:

Anxiety Disorders (Generalized Anxiety Disorder, Social Anxiety)

Depressive Disorders (Major Depression, Dysthymia)

Trauma or Abuse Disorders

Oppositional Defiant Disorder (ODD) or Conduct Disorder

Learning Disorders (Dyslexia, general academic categories, e.g., Math, English, Literature, etc.)

Substance Use Disorders

Autism Spectrum Disorder (ASD)

Tic Disorders or Tourette Syndrome

Sleep Disorders (Insomnia, Delayed Sleep Phase Syndrome)

Got Questions? Reach Out!

Contact us or take a look at our frequently asked questions using the links below! 

ADD/ADHD Scheduling and Contact 

ADD/ADHD FAQs

What Are Differential Diagnoses for ADD/ADHD?

Differential diagnosis is the process of distinguishing ADD/ADHD from other conditions that may present with similar symptoms. This is essential because many neurodevelopmental, psychiatric, medical conditions, etc., can mimic or overlap with the symptoms of ADHD, such as inattention, impulsivity, and hyperactivity. 

Differentiating these conditions ensures clients are not misdiagnosed and receive the appropriate therapeutic interventions.

Conditions Often Considered in an ADD/ADHD Differential Diagnosis

Generalized Anxiety Disorder

Major Depressive Disorder

Bipolar Disorder

Post-Traumatic Stress Disorder (PTSD)

Sleep Apnea or other medical causes of fatigue

Adjustment Disorders

Personality Disorders (e.g., Borderline or Avoidant traits)

Sensory Processing Disorders

Thyroid Dysfunction or other medical concerns

Got Questions? Reach Out!

Contact us or take a look at our frequently asked questions using the links below! 

ADD/ADHD Scheduling and Contact 

ADD/ADHD FAQs

Comorbidities and Differential Diagnoses: The Testing Process

Our ADD/ADHD Testing Process for Comorbidities and Differential Diagnoses

We believe that a proper ADD/ADHD evaluation must be comprehensive. At Calvert + Associates, psychological testing goes beyond surface-level screening. Here’s what our process includes:

Clinical Interview & Symptom History

We begin with a structured clinical interview to gather extensive information on:

Symptoms (current, onset, duration, context, and impact)

Family History/Background (e.g., ADD/ADHD diagnoses and/or symptoms)

Family of Origin (attachment, childhood experiences, family dynamics, etc.)

Academic History/Background (past and current academic performance)

Developmental History (potential developmental stage disruptions through the lifespan)

Executive Functioning (Attention, Focus, Effort, Affect, Memory, and Action)

Social Functioning (social engagement evaluations)

Emotional Functioning (emotional regulation and emotional intelligence evaluations)


Optional Multi-Source Input

We can also collect information from:

  • Parents or caregivers (for children/adolescents)
  • Spouses or significant others (for adults)
  • Teachers or supervisors (when applicable)


This helps us understand how symptoms present across environments.

Standardized ADD/ADHD Assessment Tools

We use the evidence-based assessment: Brown Attention-Deficit Disorder Scale and Diagnostic Form (for ages 3+). 

If you are looking for more information about this assessment, visit the ADD/ADHD Testing Info Page (ADD/ADHD Testing and Assessment) for a detailed breakdown of everything you'd need to know. 


As a simple step-by-step outline, this is what to expect:

  • Scale (40-50 item questionnaire relating to ADD/ADHD symptoms in multiple areas of life)
  • Diagnostic Form: Clinical interview
  • Diagnostic Form: Diagnostic Criteria Checklist (using the Diagnostic Statistical Manual, or DSM, guidelines)
  • Diagnostic Form: Screening Tools (e.g., depressive disorders, anxiety disorders, OCD, ASD, learning disorders, trauma and abuse disorders, sleep disorders, eating disorders, and many more)
  • Diagnostic Form: Integration of Additional Psychological Assessments (MMPI-3, Beck Depression & Anxiety Inventories, WAIS/WISC, and others)
  • Then we write the report!


All of this is explained in more detail on the ADD/ADHD Testing Info page, which can be read using this link: ADD/ADHD Testing and Assessment

Broad Psychological ADD/ADHD Assessment

These provide additional screening for more information if the ADD/ADHD assessment (e.g., Brown ADD Scale and Diagnostic Form - this is what we use) picks up on previously discussed comorbidities or differential diagnoses, which allows for a more comprehensive treatment plan. 

  • MMPI-3 to evaluate broader personality or mood disturbances
  • Cognitive assessments (WAIS-IV, WISC-V) to evaluate working memory, processing speed, and learning challenges (coming soon!)


More to come in the future!

ADD/ADHD Diagnostic Synthesis

All data points—clinical impressions/observations, clinical interview information, test results, functional observations, and collateral input—are synthesized to provide:

  • A formal diagnosis (if applicable)
  • Identification of any comorbid conditions
  • Rationale for ruling in/out differential diagnoses
  • Recommendations tailored to the unique presentation and needs of the client
Got Questions? Reach Out!

Contact us or take a look at our frequently asked questions using the links below! 

ADD/ADHD Scheduling and Contact 

ADD/ADHD FAQs

Why Accurate and Comprehensive ADD/ADHD Diagnostics Matter

Getting the diagnosis right from the beginning is crucial. Misdiagnosis can lead to:

  • Ineffective or harmful treatment
  • Unaddressed conditions worsening over time
  • Frustration or stigmatization


Whether you’re seeking clarity for yourself or your child, we’re here to walk with you through this journey—ensuring that every possible explanation is considered, and the most accurate conclusions are drawn.

Treatment Planning

Comorbidities often influence the specific recommendations of therapy and medication. For example, the presence of anxiety or depression may necessitate a different treatment approach than ADHD alone.

Prognosis

Comorbid disorders can worsen the prognosis of ADHD, leading to greater functional impairment and increased risk for academic, occupational, and social difficulties.

Avoiding Misdiagnosis

Many disorders share symptoms with ADHD. Careful differential diagnosis ensures that individuals receive the correct diagnosis and avoid unnecessary or ineffective treatments.

Comorbidities and Differential Diagnoses: Let's Get Started!

Schedule a Comprehensive ADD/ADHD Evaluation Today

If you or a loved one is struggling with attention, focus, restlessness, or emotional regulation, it may be more than just ADHD—or it may be something else entirely. Let us help you find clarity.


  • Office Administrator eMail: mandy@calvertandassociates.com
  • Office Administrator Phone Number: 205-918-6161 
  • Examiner eMail: michael@calvertandassociates.com


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