Panic attack symptom dimensions and their relationship to illness characteristics in panic disorder.

Subtyping panic disorder by predominant symptom constellations, such as cognitive or respiratory, has been done for some time, but criteria have varied considerably between studies. We sought to identify statistically symptom dimensions from intensity ratings of 13 DSM-IV panic symptoms in 343 panic patients interviewed with the Anxiety Disorders Interview Schedule for DSM-IV Lifetime Version. We then explored the relation of symptom dimensions to selected illness characteristics. Ratings were submitted to exploratory maximum likelihood factor analysis with a Promax rotation. A three-factor solution was found to account best for the variance. Symptoms loading highest on the first factor were palpitations, shortness of breath, choking, chest pain, and numbness, which define a cardio-respiratory type (with fear of dying). Symptoms loading highest on the second factor were sweating, trembling, nausea, chills/hot flashes, and dizziness, which defines a mixed somatic subtype. Symptoms loading highest on the third factor were feeling of unreality, fear of going crazy, and fear of losing control, which defines a cognitive subtype. Subscales based on these factors showed moderate intercorrelations. In a series of hierarchical multiple regression analyses, the cardio-respiratory subscale was a strong predictor of panic severity, frequency of panic attacks, and agoraphobic avoidance, while the cognitive subscale mostly predicted worry due to panic. In addition, patients with comorbid asthma had higher scores on the cardio-respiratory subscale. We conclude that partly independent panic symptom dimensions can be identified that have different implications for severity and control of panic disorder.