Saturday, July 1, 2017

The Nervous Theory Of Asthma: A Review

Earlier, I wrote that “Occupational Asthma” was “one of the oldest asthma subgroups.” I would like to make the case here that the oldest of oldest of oldest asthma subgroups is none other than “Nervous Asthma.” To help me make my case I thought a little history of nervous asthma would prove helpful. 

400 B.C. Hippocrates (400 B.C.) referred to asthma as epilepsy of the lungs. This is because he believed it was caused by phlegm draining down from the brain. He, therefore, believed asthma was caused by airway spasms similar to the body spasms of epilepsy. He also alluded to asthma as a nervous disorder when he said, "the asthmatic should guard himself against his own anger." 

1st Century. Galen (120-200 A.D.) is a physician who created theories about medicine that were well respected by physicians all the way up to the 19th century, and even into the 20th century. He performed one experiment (and probably on a stolen body) where he severed the spinal cord to produce asthma symptoms artificially. (1)
2nd Century.
 Maimonides (1138-1204) said nervousness makes one prone to illness and may have been the first to describe how illness can contribute to diseases. He did describe asthma, but he did not link the two.

1550. Felix Platerus (1536-1614) observed asthma symptoms when nothing wrong could be seen with the lungs. He believed asthma was caused by an obstructed pulmonary artery, although he also believed it was caused fluid flowing down from the larger nerves from the brain.

17th century. Jean Baptiste van Helmont (1579-1644) was the first physician to focus on the idea that asthma was caused by airway spasms. However, he believed this was the result of nerve irritation due to stress. He thought this was the case because no scars were observed in the lungs of asthmatic patients. He gave examples of how stress could induce asthma. In one case he described how a woman developed it just by being exposed to flowers, and in a second case, he described how a man developed it and died just after being exposed to stress.

17th century.  Thomas Willis (1621-1675) also described asthma as having occurred despite any observable changes in the person. Paul Ammann (1634-1691) described in a book of law cases how asthmatics should be absolved from crimes because the fear that resulted could result in an asthmatic attack. This meant that all asthmatics must be kept out of stressful situations.

1850’s. Dr. Henry Hyde Salter published a series of articles that were eventually published in 1960 as “On Asthma: Its Pathology and Treatment.” In these articles, later published as chapters, he proved for the medical community that asthma was due to spasms of the air passages caused by irritation of nerves. Salter’s asthma theories are frequently cited in medical texts regarding asthma for the next 50 years. Those physicians who accepted Salter’s theories -- and this consisted of most physicians -- referred to Salter’s nervous theory as the “Nervous Theory of Asthma.”

1899. Dr. Henry Osler, the Father of Modern Medicine, referred to asthma as a "neurotic affection" in his medical texts, "The Principles And Practice Of Medicine." This book would be the main textbook used by medical students much of the next century, and so would have a significant impact on shaping the views of the medical profession.

1900. The discovery of epinephrine created a lot of buzz among the medical community, and it was trialed for a variety of diseases, including asthma. This worked to confirm an old theory, that asthma was due to airway spasms, and a new theory, that asthma was due to dilated blood vessels resulting in pulmonary congestion. These theories spawned from the fact that epinephrine both dilates airways and constricts blood vessels. So, for the first time in many years, the nervous theory becomes less significant among asthma physicians.

1910. This was the year that allergies were linked with asthma. This revelation would have no immediate impact on our history, but it will within the next 20 years. 

1920’s. German physicians became infatuated with psychosomatic medicine, and out of this infatuation grew an increasing interest in the idea that asthma was a psychosomatic disorder. Among these physicians was Dr. Franz Alexander, who will make a significant contribution to our history about 30 years later.

1930’s and 1940’s. Most American physicians continued to believe that asthma was triggered by emotions. However, their main emphasis now was attempting to control allergies. Also, as researchers started learning more about allergies, they realized that asthma symptoms were the result of an abnormal immune response to allergens. Spearheading the idea that allergies caused asthma was the germ theory of asthma. At this time it was believed that most diseases were caused by bacteria or some similar substance, so this theory sort of spearheaded the idea of allergies as a contributing cause of asthma. So, the nervous theory of asthma takes a back seat to this new thinking about asthma.

At the same time that was going on, German physicians, lead by Dr. Franz Alexander, were beginning to study the relationship between asthma and psychosomatic disorders like stress, anxiety, and depression. This sort of was a rebirth of the old theory of asthma as a nervous disorder. The main theme here was that strong emotions caused by an asthmatics separation, or threat of separation, from his mother were one of the main contributing causes of asthma. One treatment for this was psychological therapy. 

1951.  By now, Dr. Franz Alexander had migrated to the United States, and here he wrote a paper listing asthma as one of the seven psychosomatic disorders. This, in turn, re-established credibility of the nervous theory of asthma for physicians in the developed world. This was also the decade that corticosteroids were first used to reduce airway inflammation that was present during acute asthma attacks.

1957. The first metered dose inhalers enter the market. They were the Medihaler Epi and the Medihaler Iso. This was a great revelation for asthmatics as it gave them a lightweight, portable, and easy to use means for obtaining quick asthma relief.

1960s.   It was also discovered that corticosteroids come with side effects. So, by the end of the 1950's, steroids were soon reserved for only the severest asthma attacks that responded poorly to other treatments. However, researchers began a quest to see if they could develop an inhaled corticosteroid steroid to reduce the risks for systemic side effects. So, this was the decade where researchers started studying the benefits of inhaled corticosteroids on asthma.

1980’s.  By 1982 two inhaled corticosteroids were on the market. Studies showed they seemed to work very well for asthmatics. Research to learn how they worked lead to the discovery that asthma was an inflammatory disorder, where all asthmatics have some degree of underlying airway inflammation. It was now well accepted that asthma symptoms occurred due to exposure to asthma triggers, which may include strong emotions and stress, but also allergens, respiratory viruses, certain foods, exercise, etc. Researchers now understood that asthma was a respiratory disease consisting of chronic underlying airway inflammation and that this inflammation worsened when exposed to asthma triggers resulting in bronchospasm, increased mucus production, and asthma symptoms. This spearheaded the quest to understanding the exact genes, cells, and biological processes responsible for asthma. Rather than focusing on asthma as a nervous disorder, asthma was considered a disease associated with an overactive immune response to innocuous substances in the air inhaled. So, this new theory set aside any notions of asthma as a nervous disorder caused by stress, anxiety, and depression. That said, nervous disorders were still thought contribute to asthma by triggering it, maybe even making it worse, but it was no longer suspected to be the causative agent. 

1990’s. You might hear things like: “While stress and anxiety are no longer thought to cause asthma, both may act as asthma triggers.” I'm not sure who came up with this line, but I have heard it over and over by various asthma experts, often without citation. This may have acted as a relief, of sorts, for asthmatics, who were tired of hearing about asthma being all in their heads. However, it offered no advantage to the many asthmatics who continued to deal with both anxiety and asthma. 

2017. Modern evidence has brought upon a resurgence, of sorts, of the nervous theory of asthma. Studies seem to show that asthma might contribute to anxiety and depressive disorders, and that anxiety and depressive disorders might contribute to asthma. This new evidence comes with a modern twist, which includes the idea that not all asthma is nervous in origin. However, knowledge of a possible link should make physicians better armed to both diagnose and treat anxiety and depressive disorders in asthmatics in an effort to help them obtain ideal asthma control.

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