According to the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), panic disorder is an anxiety disorder characterized by recurrent unexpected panic attacks consisting of physical and cognitive symptoms – such as palpitations, dyspnea, dizziness, derealisation, fear of losing control, and fear of dying – that surge abruptly and reach a peak within minutes, provoking intense fear or discomfort. Beyond the panic attacks themselves, which are the hallmark of the disorder, another key feature of panic disorder is fear (at least 1 month) of having future panic attacks, which can lead to important maladaptive changes in behaviour (i.e. anticipatory anxiety and phobic avoidance of places and situations where an attack has occurred or where individuals believe it may occur). Panic disorder frequently occurs in comorbidity with other mental disorders, such as agoraphobia, major depression disorder, and bipolar disorder. It can be chronic and disabling, cause distress and impair quality of life. 

Panic disorder has a lifetime prevalence of approximately 3.5 % in the general population and 5–8 % in primary care settings. 

Etiology of panic disorder has not been fully unfolded; however, research suggests the interaction of genetic predisposition and specific environmental factors. Panic disorder is considered a mental disorder because: 

1. Panic attacks are deemed as false alarms

It has been more than 20 years since germinal theories postulated the existence of hypersensitive alarm systems in panic disorder. According to Klein, panic attacks occur when the suffocation alarm system is erroneously triggered. 

Gorman’s neuroanatomical model postulates panic attacks are conditioned fear responses mediated by an overly sensitive fear network; the three alarms (true, false, learned) theory deems panic attacks as the results of both spontaneous firing of the fear system and conditioning processes to internal or external cues. 

Clark considers panic attacks catastrophic misinterpretations of harmless bodily sensations. These theories share the assumption that alarms are false because individuals with Panic Disorder are physically healthy. 

2. Panic disorder is treated with psychotropic drugs and/or psychotherapies

Withal there has been some debate whether to consider panic disorder just a mental disorder. Beside cognitive symptoms, individuals with panic disorder often complain of several somatic symptoms including respiratory difficulties, irregular heartbeat, dizziness, and photophobia. Usually, after conducting standard procedures (such as physical and/or clinical tests), physicians and psychiatrists reassure individuals that their bodies function perfectly, and they ascribe the somatic symptoms entirely to anxiety.

Numerous scientific findings suggest that individuals with panic disorder may also suffer from subclinical abnormal organic systems functioning (e.g. in the cardio-respiratory and the balance systems), which may be associated with hyperreactivity to hypercapnic and hypoxic inhalations, subclinical autonomic hyperreactivity, and space and motion discomfort.

Respiration in Panic Disorder

Respiratory symptoms are very frequent among individuals with panic disorder, both during spontaneous panic attacks and during daily-life, and constitute a hallmark of panic attacks and panic disorder. Further information corroborates this correlation. 

First, an association between panic disorder and hyperventilation is known. Up to 40% of individuals with panic disorder suffer from hyperventilation. However, chronic hyperventilation does not seem to be unique of panic disorder. In fact, it is also prevalent in individuals suffering from other anxiety disorders and it may just reflect background anxiety. 

Second, an association between panic disorder and respiratory diseases has been found.  Up to 40% of individuals with panic disorder have a history of respiratory disease, in particular asthma and bronchitis. The nature of this association remains largely unknown. It may be that either panic attacks precede the onset of respiratory disease or that respiratory or lung disease leads to the development of panic attacks. Alternatively, a third factor (e.g. cigarette smoking) may increase co-occurrence of respiratory disease and panic attacks.

Third, individuals with panic disorder showed subclinical abnormalities in respiratory patterns. This might lead to respiratory distress, hyperventilation and, eventually, to a panic attack. Also, individuals suffering from panic exhibit respiratory irregularity, which may be a vulnerability factor to panic attacks.

Cardiovascular System and Panic Disorder

Heart palpitations or a racing heart, and chest pain or discomfort are among the core somatic symptoms that characterize panic attacks. Subjects who experience panic attacks are often concerned they may suffer from a cardiac disease or that they are dying of a heart attack and repeatedly refer to the emergency room. Although routinely cardiac examination yields a negative result, the symptoms that these subjects experience feel are so real that reassurance from the doctors is not enough to convince them that their cardiovascular system performs normally. Most of these individuals believe there might be some undetected abnormality in their cardiovascular system. As a result, they tend to worry about future attacks and develop anticipatory anxiety, which negatively impacts their quality of life and daily functioning.

In actual fact, a link between panic disorder and cardiac disorders has emerged. For instance, many studies described imbalanced autonomic regulation and reduced heart rate variability in patients with panic disorder. Finally, repeated panic attacks may be disturbing for the cardiorespiratory system and may contribute to increased cardiac risk in this population over time.

Panic Disorder and the Balance System

Prevalence of vestibular symptoms – such as vertigo, instability, and lightheadedness – is high in individuals suffering from panic disorder. Up to 75% of individuals with panic disorder manifests postural instability. Moreover, vestibular disorders seem to be more prevalent in individuals with panic disorder and agoraphobia than in individuals with panic disorder alone.

Respiration and the balance system are intertwined and such connections may partially explain the association between hyperventilation and postural instability in individuals with panic disorder (who are in fact in a chronic state of hyperventilation). Chronic hyperventilation contributes to postural instability and might aggravate dizziness in subjects with panic disorder.

In conclusion, individuals with panic disorder may present subclinical abnormalities in their balance system. Such vestibular instability may be linked to changes in homeostatic autonomic responses which in turn would trigger affective and emotional responses, including panic.

Balance and the Visual System in Panic Disorder

Maintaining proper balance and posture partly depends on visual information. There is evidence that in individuals with panic disorder, anxiety and discomfort may arise when visual information is inaccurate. Individuals with panic disorder, especially those with comorbid agoraphobia, might be hypersensitive to the influence of peripheral visual system on balance.

Photosensitivity and Panic Disorder

Photosensitivity (i.e. an abnormally high sensitivity to light exposure) seems to contribute both to the etiopathogenesis of and response to therapy in panic disorder. In fact, individuals with panic disorders have a lowered threshold of tolerance to light and develop the tendency to adopt photophobic behaviour when compared to healthy controls. For example, they tend to protect themselves from light by wearing sunglasses and/or by avoiding to go out during the daytime.

Conclusions and Clinical Implications

Individuals with panic disorder often complain of somatic symptoms such as abnormalities in the cardiorespiratory and vestibular systems. They exhibit poorer physical fitness, higher respiratory variability during mild physical activity, higher respiratory dysfunctions/breathing patterns irregularities, as compared with individuals without panic disorder.

Putting these findings together partially contradict the assumption that panic attacks are just false alarms. Panic attacks may be real alarms and reflect reduced adaptability to changes and true homeostatic instability, which may sustain the experience of anticipatory anxiety and phobic avoidance and increase vulnerability to panic. 

In conclusion, individuals with panic disorder may be physiologically different from healthy subjects and that cardiac, respiratory, and balance symptoms may be the outcome of the inability of these systems to relate with the environment.