According to the DSM-IV, panic disorder is classified as an anxiety disorder consisting of repeated and unexpected panic attacks. Panic attacks are defined as discrete events characterized by the sudden onset of cardiorespiratory symptoms and physiological arousal, accompanied by catastrophic fears and the urge to flee. Typically, these symptoms include shortness of breath, tachycardia, nausea, sweating, and fears that the individual is losing control or going crazy. Such spontaneous panic attacks typically reach an apex of intensity within 10 minutes.
Data from large scale epidemiological surveys suggest that panic disorder is more common in women than in men (Joyce et al., 1989; Katerndahl and Realini, 1993; Reed and Witchen, 1998). The National Comorbidity Survey (NCS) examined the presence of psychiatric morbidity, including depression, panic disorder and general anxiety, in a large national sample (Kessler et al., 1994).
Based on NCS data, Eaton et al. (1994) found that panic disorder is 2.5 times more prevalent among women than men. In addition, the gender difference appears to increase according to age. For example, the prevalence rate of panic disorder for women ages 15 to 24 was 2.5%, compared to 1.3% of same-age men. For older women and men, the overall rates drop, but the difference between genders appears to grow. Among women ages 35 to 44, the rate of panic disorder was 2.1%, compared to the 0.6% rate among same-age men.
In addition to higher prevalence rates, women may suffer more debilitating forms of panic disorder. Yonkers and colleagues (1998) conducted a longitudinal study of 412 women and men diagnosed with panic disorder with and without agoraphobia for five years. This study found that after remission, panic symptoms reoccurred at twice the rate for women than men. Still other studies have shown that females suffer a significantly greater frequency of panic attacks than men (Maier and Buller, 1988).
We examined gender differences of specific panic-related symptoms using empirical data drawn from the NCS (Sheikh et al., 2002). Specifically, the frequency of 18 panic symptoms was examined according to the gender of patients with panic disorder (n=274) and patients with panic attacks only, but without meeting criteria for panic disorder (n=335).
Findings from this study suggested that heart pounding was the most frequently endorsed panic symptom for both genders and both diagnostic groups. However, in the panic disorder group, a significantly greater proportion of women than men endorsed shortness of breath (72% versus 50%), feeling faint (59% versus 45%) and feeling smothered (60% versus 43%). In the panic attack only group, women were more likely to complain of shortness of breath (65% versus 50%), choking or difficulty swallowing (37% versus 25%), and feeling smothered (50% versus 38%).
Using logistical regression, three symptoms predicted female gender: shortness of breath, nausea and feeling smothered. Two symptoms predicted male gender: sweating and pain in the stomach (Table).
Overall, the results of our study indicated that some gender differences do exist at the symptom level for panic disorder and panic attacks. Specifically, a significantly greater proportion of females appear to suffer respiration-related symptoms (difficulty breathing, feeling faint and smothered). Several theories are described here that show how adaptive physiological monitors for breathing and modulation of pain, coupled with fluctuations in the sex hormone cycle, may lead to panic.
Premenstrual hormonal fluctuations may partially explain the increased incidence of panic disorder in women. Seeman (1997) suggested that progesterone(Drug information on progesterone) metabolites have anxiolytic effects due to their agonistic effect on g-aminobutyric acid (GABA)/benzodiazepine receptors. However, Stein et al. (1989) were unable to demonstrate increased anxiety ratings in normally menstruating females with panic disorder across two menstrual cycles. Nevertheless, other studies point to greater panic response in females suffering from premenstrual dysphoric disorder, indicating that a possible concurrent dysregulation of the GABA/benzodiazepine receptor complex may underlie aspects of both the panic response and disorders related to the female reproductive cycle.
Premenstrual hormonal fluctuations may also explain the increased frequency of respiratory-related symptoms in women with panic disorder (Klein, 1993). According to the suffocation false alarm theory, there is a suffocation alarm system that becomes unduly hypersensitive. Therefore, ordinary physiological fluctuations in blood carbon dioxide levels and brain lactate may be interpreted as impending asphyxiation. Such overreactions on the part of the suffocation alarm system initially release a sense of breathlessness or dyspnea, followed by hyperventilation, panic and the urge to flee. Another indication that female physiology may have a particular relationship to panic disorder came from challenge studies with CO2 and lactate. Although panic responses to such challenges only occur in panic disorder, women with premenstrual syndrome show similar respiratory difficulties as patients with panic disorder (Harrison et al., 1989; Sandberg et al., 1993).