Brief report
Acute exercise reduces the effects of a 35% CO2 challenge in patients with panic disorder

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Abstract

Background

Chronic exercise has been shown to have therapeutic effects in panic disorder (PD). The mechanism of these effects is unknown. Acute exercise reduces the effect of a panic challenge in healthy volunteers. Such an effect has not yet been demonstrated in PD patients. The present study aimed at exploring the antipanic effects of acute exercise on a 35% CO2 panic provocation in treatment-naïve PD patients to further elucidate the mechanisms of the beneficial effects of exercise on panic.

Methods

Eighteen PD patients performed either moderate/hard exercise or very-light exercise before a 35% CO2 challenge in a randomized, between-group design. The reactivity to CO2 was assessed with the Visual Analogue Anxiety Scale and the DSM-IV Panic Symptom List.

Results

Panic reactions to CO2 were smaller in patients that performed moderate/hard exercise in contrast to those that performed very-light exercise. Increments in both measurements and panic rates were consistently reduced by intense exercise.

Limitations

Since this study focuses on the acute effects of exercise on CO2 sensitivity in patients with PD, the results of repetitive exercise sessions on the rate of spontaneous panic attacks and overall symptoms are warranted. The small sample size and other limitations are addressed.

Conclusions

Exercise reduced the panicogenic effects of a CO2 challenge. In addition to its therapeutic potential, exercise may also be useful as a laboratory maneuver with heuristic value in experimental research into the mechanisms of antipanic treatment.

Introduction

Exercise has long been regarded as a healthy behavior with both preventive and therapeutic properties for a variety of physical and mental pathological conditions (U.S. Dept. of Health and Human Services, 1996). With regard to mental disorders, much focus has been placed on the relationship between exercise and affective disorders (De Moor et al., 2006, Harris et al., 2006). In line with the beneficial effects of regular physical activity on mental wellbeing, a 10-week exercise treatment program for panic disorder has shown to be as effective as a standard antipanic pharmacological intervention and superior to placebo (Broocks et al., 1998). It is however unclear if these beneficial effects were due to changes in aerobic metabolism or to the behavioral exposure effects of running therapy.

Intense acute physical activity induces changes in the anxious state of healthy and anxious individuals (de Coverley Veale, 1987). In the case of panic disorder patients, anxious symptoms increase proportionally to the intensity of exercise when compared to healthy subjects (Stein et al., 1992). Yet unexpectedly, patients can well tolerate sub-maximal exercise causing lactate elevations that are comparable to those of a panicogenic lactate infusion (Stein et al., 1992). A pilot study with healthy volunteers, aimed at gaining insight in this apparently contradictory phenomenon, showed that acute exercise reduced the effect of a challenge with 35% CO2, despite lactate elevations similar to those used in an infusion capable of provoking panic attacks (Esquivel et al., 2002). Moreover, in other studies with normal subjects, acute exercise has shown to minimize the anxious symptoms provoked by both caffeine (Youngstedt et al., 1998) and cholecystokinin (CCK) (Strohle et al., 2005). A similar effect has not yet been documented in subjects with panic disorder. Accordingly, this study was designed to explore the antipanic effects of exercise on a 35% CO2 panic provocation in treatment-naïve panic disorder patients.

Section snippets

Methods

Eighteen panic disorder patients from the outpatient clinic of the Instituto Nacional de Psiquiatría Ramón de la Fuente in Mexico City (eleven women and seven men; mean age 29.6 years, SD = 8.2) were invited to voluntarily participate in the study. Patients with panic disorder (with or without agoraphobia in accordance to the DSM-IV) as main diagnosis made by at least two clinicians and a structured psychiatric interview (Sheehan et al., 1998) were included for the study. All subjects were free

Results

Mean age of both experimental (N = 10) and control (N = 8) groups were not significantly different (30.1 years, SD = 8.9; and 29.1 years, SD = 8.0; t =  0.241, df = 16, p = 0.81; respectively). Sex and comorbid axis I diagnosis distribution were similar among groups. All subjects with 2 diagnoses (N = 11) had a mild to moderate major depressive disorder and those with 3 diagnoses additionally had social anxiety (N = 1) and generalized anxiety disorder (N = 1).

At the beginning of the session, blood lactate levels (t

Discussion

Exercise reduced the panicogenic effects of a 35% CO2 challenge in patients with PD. Compared to the control condition, the CO2 elicited increase in panic symptomatology expressed on the PSL and the VAAS was significantly reduced in the exercise group. Panic attacks were more frequent after very-light exercise than after moderate/hard exercise. Because the panic attack definition used in this study was fairly restrictive, an additional analysis with a less stringent criteria (an increase of ≥ 

Role of funding source

No specific grant was used to conduct this study.

Conflict of interest

None of the authors report competing interests.

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