Using Medical History to Differentiate Between Bipolar Disorder and ADHD: Exploring the Differential Diagnosis

Accuracy of diagnosis is critical before treating bipolar disorder, ADHD, or the two together. However, high rates of comorbidity and a constellation of overlapping symptoms make the task of distinguishing between bipolar disorder and ADHD especially challenging.

According to a recent meta-analysis of 71 studies in 18 countries published in Neuroscience and Biobehavioral Reviews, 1 out of 13 people with ADHD also had bipolar disorder. Among patients with bipolar, 1 out of 6 also had ADHD.1 The co-existence is clearly present. So, if you run a mood disorders clinic and you tell me you don’t have ADHD patients, I’ll say maybe you don’t see patients for their ADHD, but you certainly have ADHD patients.

In terms of differentiating the two disorders, there’s much talk about executive function subsumed under ADHD, and about emotional dysregulation subsumed under mood disorders, including major depression and bipolar disorder. However, we know that cognitive symptoms and executive dysfunction exist in patients with bipolar disorder. We also know that emotional dysregulation is a component of ADHD; the more severe the ADHD, the more severe the emotional dysregulation.

This connection is borne out by a recent study conducted with 150 ADHD patients, 335 adult bipolar patients, and 48 controls, in which subjects used two self-report scales. Adult ADHD patients displayed higher emotional dysregulation, and emotional responsiveness at levels equal to that seen in the patients with bipolar disorder.2 So, if you rely on levels of emotional dysregulation or executive dysfunction to differentiate the disorders, you may be led amiss diagnostically.

This confusion is partly a result of the shortcomings of descriptive psychiatry. Descriptive psychiatry is the use of words to describe the psychological experience. According to the DSM-5, patients with bipolar disorder experience the following: increased talkativeness, racing thoughts, distractibility, fidgety and restless, increased risky behavior, impulsive decisions. Certainly, the experts who wrote the DSM-5 endeavored to use language specific to the diagnostic entity, but it’s clear that these descriptions could just as easily be used to describe ADHD. In other words, it’s very difficult to make these diagnostic distinctions solely based on symptom checklists or a clinical interview that focuses only on the immediate symptoms.

To arrive at an accurate differential diagnosis, a clinician must carefully consider family psychiatric history and dial into the patient’s phenomenological experience. The latter focuses on specific symptoms and qualitative nature. For example, there is a qualitative difference between a tension headache and a migraine headache, even though both are headaches. The same difference can be seen in sadness vs depression — a qualitative difference in the psychological experience. Diagnostic accuracy is further increased by considering symptom trajectory over time (periodicity and chronicity) and family psychiatric history.

The Systematic Treatment Enhancement Program for Bipolar Disorder (STEP) study looked at 1,000 adults with bipolar disorder. The overall lifetime prevalence of comorbid ADHD in this group of bipolar patients was 9% to 10%, and the onset of bipolar disorder came approximately five years earlier for those with ADHD versus those without ADHD.3 The meta-analysis published in Neuroscience and Biobehavioral Reviews revealed similar findings: bipolar disorder onset was four years earlier in the presence of ADHD.

Let’s translate that clinically. You’re treating a 15-year-old, diagnosed at age 10 with ADHD, who has just had their first major depressive episode. Do you consider the depressive episode as an outcome of ADHD because the teen is having difficulties at school? The psychological circumstances of the psychosocial stressors would make it seem legitimate that this is a major depressive episode. But we also know that, in patients with ADHD and bipolar disorder, bipolar emerges years earlier than we might otherwise expect and is usually experienced first as a depressive episode. If we consider that the patient has a family history of bipolar disorder, the diagnostic outlook changes, along with the pharmacologic considerations.

If you’ve ever had a psychiatric illness, you’ll understand that you don’t have symptoms. You have experiences. So, when patients use the term anxiety or depression or ADHD, I don’t ask, “What are the symptoms of your anxiety, or depression, or ADHD?” I ask them, “Tell me how you experience that.” This addresses the phenomenologic experience of the patient and aids the clinician in discerning the most likely diagnostic category to consider.

This, in turn, allows you to identify the unique target experiences (symptoms) that can be tracked during the course of treatment options. For the ADHD individual, these target symptoms are unique to them and fall into the categories of cognitive difficulties, emotional reactivity, and executive functioning. From a clinical perspective, it becomes clear that a phenomenological approach to symptoms makes it easier to sort out diagnostic comorbidities. In doing so, the target symptoms for each disorder become clear, thereby making easier the assessment of improvement for each disorder. This approach facilitates the sequence of pharmacologic and psychotherapeutic treatment options. Given the complexity of this thought process, formal clinical training for health care providers is critical.

The content for this article was derived, in part, with permission from “ADHD, Bipolar and Substance Use: Translating Data from Clinical Data into Your Practice.” presented by David Goodman, M.D., FAPA at the APSARD 2023 Annual Conference.

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