Panic disorder (PD), a common and impairing anxiety syndrome, is generally readily diagnosable and treatable. Its phenomenology is diverse, including acute fear episodes (spontaneous and cued panics), anticipatory anxiety, and physical sensation sensitivity. PD is also frequently accompanied by agoraphobia and is more likely to affect women.
Concerning the natural history of PD, approximately one-third of patients have a clinical remission with standard interventions (pharmacotherapies and cognitive behavioral therapy [CBT]), without subsequent episodes. In another third, the course of the illness is characterized by recurrent episodes, which remain treatment-sensitive. However, a third go on to have chronic, persistent symptoms—and the majority of these patients have treatment-resistant panic (TRP).1
Treatment resistance in PD
Treatment resistance in PD may be apparent or real. Apparent treatment resistance may be due to a range of clinical factors including unstable psychiatric and medical comorbidities, patient adherence problems, clinician availability (important to PD patients early in treatment), or therapeutic alliance problems, often driven by cognitive and behavioral avoidance. Other treatment-related factors to consider are medication intolerance/pharmacokinetic issues, treatment acceptability, access to care, and treatment costs. However, despite a careful review of the diagnosis and adjustments to the treatment plan, a number of patients will have ongoing, real TRP.
Exactly what constitutes treatment resistance in PD is a topic of debate. However, one clinical definition is continued partial response, or non-response, after 6 months of optimal treatment with at least 2 standard, evidence-based interventions.2
A straightforward measurement-based approach can complement this clinical guideline. The Panic Disorder Severity Scale (PDSS), a commonly used outcome in PD clinical trials, is also an excellent scale for general clinical use.3 It is a brief, clinician-rated assessment that consists of 7 items (each rated 0 to 4), which sample different domains of PD symptoms. In clinical trials, a PDSS total score of 4 or lower is often considered a clinical remission, while a clinical response is frequently defined as a 50% reduction from the baseline PDSS total score.
Some experts suggest that patients should not have an individual PDSS item score higher than 1 to qualify for remission status. Thus, by PDSS criteria, TRP patients will have only a partial or limited response to specific interventions and, over the course of treatment, will fail to achieve a remission state.
Dr. Goddard is Professor of Psychiatry, University of California at San Francisco, UCSF Fresno Medical Education & Research Program, Fresno, CA. Dr. Goddard receives royalties from UpToDate for an on-line manuscript publication; he is also the recipient of pilot grant funds from the National Network of Depression Centers (NNDC) for a multisite ketamine trial.
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