Differential Diagnosis: Why It’s Important and Why You Should Care

By: Dr. Cassandra M. Faraci


Hindsight leaves me feeling very fortunate that a big part of my graduate school training was on the assessment period, using evidence-based measures, and spending time on differential diagnosis. When I opened the Center for Anxiety and Behavior Management in 2016, I designed the practice’s procedures to begin the psychotherapy process with a significant amount of time gathering information about the unique individual in front of me. As the demand for services increased and our staff grew, each clinician was trained heavily on the assessment period. Why? Because it’s that important to the success of the treatment.

What is differential diagnosing?

According to the American Psychological Association, a differential diagnosis is, “…the process of determining which of two or more diseases or disorders with overlapping symptoms a particular patient has” and “…the distinction between two or more similar conditions by identifying critical symptoms present in one but not the other” (https://dictionary.apa.org/differential-diagnosis). The challenge in mental health is that there aren’t blood tests, for example, that clinicians can run to rule in or out specific diagnoses. We have to use questions. We have to process answers to those questions to then know what the next set of questions can be. We need to have a solid understanding of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR) to even know which diagnoses have which symptoms and when we can rule certain ones out. Many of us use interviews with family members, teachers, etc. to gather data. A few of us use norm-referenced rating scales to be able to compare responses to same-aged peers who do not have diagnoses so that we have a sense of what falls in the normal range of human behavior and what would be considered out of the normal range. In my experience, it’s rare to find clinicians with extra training in differential diagnosing. At the Center for Anxiety and Behavior Management, clinicians are trained in differential diagnosis and begin their employment with us having supervision and case consultation on the diagnostic process to ensure reliability.

Why is differential diagnosing important?

  • Accurate diagnosing. This helps us distinguish between mental health diagnoses with similar symptoms. For example, when a patient reports “anxiety” as a symptom, this does not tell us which anxiety disorder is present or if it’s secondary to another non-anxiety diagnosis.
  • Avoidance of Misdiagnosing. It also helps us reduce the risk of concluding the wrong diagnosis which can lead to ineffective treatment strategies. We don’t want to head down an incorrect path and waste anyone’s time.
  • Identifies Comorbidities. Did you know that many people with mental health issues have more than one diagnosis? Doing a differential diagnostic interview should lead a clinician to consider all options and not just stop at the first one that makes sense.
  • Informed Decision-Making. When we’ve considered all options and thoughtfully made our conclusions, we can choose the most appropriate strategies informed by science to be most effective for the given diagnoses. This leads us to…
  • Effective Treatment Planning. Now that we’re informed, we can tailor treatment strategies to each person’s or family’s unique needs. We shouldn’t be guessing or using the same strategies for everyone. By this point, we should have a good idea of what’s going on and can pull from our “clinician’s toolbox” to find the right “tool” for the issue being considered. This leads to…
  • Higher Success Rates. Instead of randomly choosing strategies and waiting to see if they work, clinicians should have a solid idea of which strategies are the most likely to be effective. This means faster success, less sessions needed, less out-of-pocket expenses, and most importantly, a person who is spending less time suffering.

We’ve had many patients come through our doors, and many of them come with incorrect diagnoses and/or missed diagnoses. Why does this happen? There are so many reasons, but to name a few: (1) no differential diagnosis was done, (2) “tunnel vision” in clinicians in which they tend to pay attention to a few details and miss other important information (often diagnosing the most obvious disorder without considering the whole picture), (3) a rushed assessment process, (4) lack of knowledge of the DSM-5-TR, or (5) not enough data was gathered. An example of (1) would possibly be a clinician who does not ask enough questions to rule in and out symptoms of multiple possible diagnoses. An example of (2) that we often see is when someone comes to us with a diagnosis (from another facility) of Attention-Deficit/Hyperactivity Disorder (ADHD) because he or she reported having attention issues; however, many DSM-5-TR diagnoses have attention issues as a symptom, and a patient is at risk of misdiagnosis if the diagnostician didn’t consider all options before concluding with an ADHD diagnosis. We might see (3) when a clinician asks a few questions and immediately has a diagnosis. I hope (4) doesn’t happen often, but not all training is created equal, and not all clinicians stay updated equally. We’d see (5) if collateral information is not gathered. At Center for Anxiety and Behavior Management, we not only interview the adult patient or parents of a minor but ask for permission to contact anyone who can provide us with more information (partners, schools, etc.). We provide norm-referenced rating scales, ask to see any records available (medical, school, etc.) and then provide a feedback session so that we can explain to the patient what our diagnoses are, what those diagnoses mean, possible causes of these diagnoses, factors that maintain the bothersome thoughts, feelings, and behaviors of these diagnoses, and what our treatment recommendations are.

In almost every community education event I run, I begin all topics with informing the audience of the importance of differential diagnosis. It’s just that important. In line with one of our missions to dispel myths and provide our community with evidence-based mental health information, we want anyone who will listen to be mindful of differential diagnosis and to make sure the chosen clinician is engaging in this process in a thoughtful manner.

I hope that this article gives you something to think about and makes you a more informed consumer of psychological services.

If you have any questions about our office and the psychotherapeutic process, please call us (908) 914-2624 or email us at info@anxietyandbehaviornj.com.

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