Classification of panic attack subtypes in patients and normal controls in response to biological challenge: implications for assessment and treatment.

Panic attacks are symptomatically heterogeneous but efforts to describe such heterogeneity are relatively new. With regard to symptom presentation, at least three types of panic attack have been proposed based on the coupling or decoupling of verbal-cognitive and physiological symptoms: prototypic, cognitive, and nonfearful panic. The central aim of the present study was to address whether patients with panic disorder (PD) and nonclinical controls (NC) could be classified and discriminated (within and between groups) in terms of subtypes of panic attacks based on convergence and divergence of physiological and subjective arousal. Two samples of patients with PD (n = 94) and NC (n = 70) were exposed to single-breath vital capacity (VC) inhalations of 35% CO2/65% O2. Subjective anxiety and cardiovascular (heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DSP)) reactivity to the challenge were measured. For reactive participants, response patterns suggested the production of differentiated and stable panic attack subtypes described as: (1) prototypical (high subjective, high physiological), (2) cognitive (high subjective, low physiological), and (3) nonfearful (low subjective, high physiological). Subtype frequency differed between groups (prototypical: 33% PD, 8% NC; cognitive: 37% PD, 4% NC; nonfearful: 11% PD, 42% NC). A panic attack typology based on convergence and divergence of different response systems appears to reliably discriminate patients with panic disorder and may have relevance for predicting clinical characteristics, treatment modality, and prognosis.