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Panic disorder (PD) is common among asthma patients and is associated with worse asthma outcomes. This may occur because of psychophysiological factors or cognitive/affective factors. This study evaluated the impact of panic attacks (PAs) on bronchoconstriction and subjective distress in people who have asthma with and without PD.A total of 25 asthma patients (15 with PD who had a PA [PD/PA], 10 without PD who did not have a PA [no PD/no PA]) were recruited from an outpatient clinic. They underwent a panic challenge (one vital capacity inhalation of 35% carbon dioxide [CO2]) and completed the Panic Symptom Scale, the Subjective Distress Visual Analogue Scale, and the Borg Scale before and after CO2. Forced expiratory volume in 1 second was assessed pre- and post-CO2; respiratory (i.e., CO2 production, minute ventilation, tidal volume) was continuously recorded, and physiological measures (i.e., systolic and diastolic blood pressure [SBP/DBP]) were recorded every 2 minutes.Analyses adjusting for age, sex, and provocative concentration of methacholine revealed no significant differences between groups in forced expiratory volume in 1 second change after CO2 inhalation (F(1, 23) < 0.01, p = .961). However, patients with PD/PA reported more panic (F(1, 22) = 18.10, p < .001), anxiety (F(1, 22) = 21.93, p < .001), worry (F(1, 22) = 26.31, p < .001), and dyspnea (F(1,22) = 4.68, p = .042) and exhibited higher levels of CO2 production (F(1, 2843) = 5.89, p = .015), minute ventilation (F(1, 2844) = 4.48, p = .034), and tidal volume (F(1, 2844) = 4.62, p = .032) after the CO2 challenge, compared with patients with no PD/no PA.Results, presented as hypothesis generating, suggest that asthma patients with PD/PA exhibit increased panic-like anxiety, breathlessness, and a respiratory pattern consistent with hyperventilation that was not linked to statistically significant drops in bronchoconstriction.