Elsevier

Biological Psychiatry

Volume 70, Issue 10, 15 November 2011, Pages 985-991
Biological Psychiatry

Archival Report
Do Unexpected Panic Attacks Occur Spontaneously?

https://doi.org/10.1016/j.biopsych.2011.05.027Get rights and content

Background

Spontaneous or unexpected panic attacks, per definition, occur “out of the blue,” in the absence of cues or triggers. Accordingly, physiological arousal or instability should occur at the onset of, or during, the attack, but not preceding it. To test this hypothesis, we examined if points of significant autonomic changes preceded the onset of spontaneous panic attacks.

Methods

Forty-three panic disorder patients underwent repeated 24-hour ambulatory monitoring. Thirteen natural panic attacks were recorded during 1960 hours of monitoring. Minute-by-minute epochs beginning 60 minutes before and continuing to 10 minutes after the onset of individual attacks were examined for respiration, heart rate, and skin conductance level. Measures were controlled for physical activity and vocalization and compared with time matched control periods within the same person.

Results

Significant patterns of instability across a number of autonomic and respiratory variables were detected as early as 47 minutes before panic onset. The final minutes before onset were dominated by respiratory changes, with significant decreases in tidal volume followed by abrupt carbon dioxide partial pressure increases. Panic attack onset was characterized by heart rate and tidal volume increases and a drop in carbon dioxide partial pressure. Symptom report was consistent with these changes. Skin conductance levels were generally elevated in the hour before, and during, the attacks. Changes in the matched control periods were largely absent.

Conclusions

Significant autonomic irregularities preceded the onset of attacks that were reported as abrupt and unexpected. The findings invite reconsideration of the current diagnostic distinction between uncued and cued panic attacks.

Section snippets

Participants

Forty-three patients with PD with or without agoraphobia were recruited through advertisements to participate in a treatment study (24). Patients' mean age was 41.6 years (range 23–61). The majority were Caucasians (81.8%), 9.1% were Hispanic, and 9.1% were Asian. Patients met the following inclusion criteria: DSM-IV principal diagnosis of PD and age 18 to 65, with the following exclusion criteria: no evidence of an organic mental disorder, suicidality, schizophrenia, alcohol or drug abuse or

Panic Attack Self-Reports

The median length of the 13 PAs was 8 minutes (range = 1–30, M = 10.6). 38.4% of the PAs occurred when the patient was alone, 23.1% in the presence of friends, and 38.5% with family. One PA occurred during sleep. 69.2% of PAs were reported as unexpected. Among the expected attacks, two occurred at home (no trigger listed), one “on the freeway,” and one “during an argument with friend.” With the exception of driving, none of the situations were previously listed by the patients as PA triggers.

Discussion

Using a novel analysis to detect points of significant change in continuous physiological time series, we found that the hour preceding the onset of naturally occurring panic attacks was marked by significant cardiorespiratory instability. These changes were largely absent in the control periods. The physiological instabilities occurred in repeated bouts often initiated by HR accelerations. The period surrounding panic onset was dominated by respiratory changes. Before panic onset, VT decreased

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