Illness Anxiety Disorder (IAD) vs Obsessive-Compulsive Disorder (OCD)
Written by: Katie Cunningham, MA, LCPC
Anxiety, Uncertainty, and Case Conceptualization
Nearly five years ago, the COVID-19 pandemic fundamentally changed how many people think about health. Illness-related anxiety became widespread and, in many cases, understandably so. While for some this was a new experience, others found themselves deeply familiar with health-focused fear and uncertainty. As a society, we engaged in ongoing conversations about risk, prevention, and responsibility. In the years since, an important clinical question has emerged: when does health-related concern shift from reasonable to obsessive or life-interfering? As therapists, we frequently treat OCD and a variety of anxiety disorders, but this work becomes more complex when the subject of fear is something as significant and personal as one’s health.
Diagnostic Overview
Obsessive Compulsive Disorder (OCD) is defined by obsessions (intrusive, unwanted, recurrent thoughts, images, urges, or doubts) and/or compulsions (repetitive behaviors or mental acts performed to reduce the distress). Symptoms must be time-consuming (e.g., take more than one hour per day) or cause significant impairment.
Illness Anxiety Disorder (IAD), formerly “hypochondriasis,” involves preoccupation with having or acquiring a serious illness, despite minimal or no somatic symptoms. Key features include persistent health anxiety lasting at least six months, heightened alarm about bodily sensations, and excessive health-related behaviors (e.g., reassurance seeking, checking) or avoidance. IAD may present as a care-seeking or care-avoidant.
If a client experiences significant, medically confirmed symptoms (e.g., chronic pain, fatigue, dizziness), Somatic Symptom Disorder may be more appropriate.
Similarities and Differences
OCD and IAD share many features: persistent fear, preoccupation, reassurance seeking, avoidance, body checking, and significant impairment in functioning and relationships. Key differences lie in the process and focus. In OCD, health anxiety typically begins with an intrusive obsession followed by compulsive behaviors or mental rituals aimed at neutralizing distress. Anxiety is often secondary to the obsession. OCD may involve multiple themes that shift or coexist over time.
In IAD, the preoccupation centers exclusively on health. Individuals tend to misinterpret normal bodily sensations as signs of serious illness and engage in disproportionate checking or avoidance. While these behaviors resemble compulsions, they are not typically ritualized in the same way as OCD. The feared illness may change, but the fixation remains health-focused.
Broadly speaking, OCD often involves effort to prevent harm, whereas IAD centers on confirming or avoiding a feared medical “truth.”
Treatment Considerations
Exposure and Response Prevention (ERP) is considered the gold standard treatment for OCD and is highly effective for IAD as well. ERP involves gradual exposure to feared stimuli while resisting compulsions or safety behaviors. Over time, distress decreases through habituation, and clients build tolerance for uncertainty.
When applying ERP to health-related anxiety, clinicians must differentiate between compulsions (OCD) and safety behaviors (IAD.) Common interventions include interoceptive exposures to normalize bodily sensations and imaginal exposures targeting catastrophic interpretations.
Continuous evaluation of ethical boundaries is essential. ERP is not appropriate when a client has unresolved medical concerns or presents with red flags (e.g., significant weight loss, neurological symptoms). Collaboration with a client’s primary care provider can provide reassurance for the clinician, not the client. When fears persist despite medical clearance and are driven by intrusive anxiety rather than illness, ERP is appropriate.
Health-Related Exposure Examples
- Touching feared surfaces without washing
- Reading about feared illness without reassurance seeking
- Writing or reading statements like, “It’s possible I was exposed to an illness today”
- Using public spaces without excessive precautions
- Observing bodily sensations without interpretations or checking
- Engaging in interoceptive exercises (e.g., increasing heart rate, inducing dizziness)
- Reading about diagnostic uncertainty or medical error
The goal is not reassurance, but distinguishing between probability and possibility, and ultimately, learning to sit with discomfort and uncertainty.
Why Diagnosis Still Matters
While OCD and IAD are often treated similarly, accurate diagnosis helps clients better understand their symptoms and anticipate patterns. OCD-related health anxiety may represent one of many shifting themes, whereas IAD involves a persistent health-focus lens. Recognizing these distinctions allows for earlier, more precise intervention. Many people casually refer to themselves as “hypochondriacs,” but their experience may reveal very real, distressing conditions that deserve thoughtful assessment and evidence-based care.
OCD vs. IAD
PDF: Diagnostic Considerations & Treatment Interventions
Sources
French JH, Hameed S. Illness Anxiety Disorder. [Updated 2023 Jul 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554399/
Stoddard, G. (2023, May 12). Illness Anxiety Disorder vs. OCD. NOCD.
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