According to the Global Asthma Report 2018, more than 339 million people worldwide suffer from bronchial asthma. About 250,000 people die of this chronic disease, although this could be avoided by adequate therapy.

Studies on the therapeutic potential of cannabis as a medicine for respiratory diseases have been going on since the 1970s. It has been shown that medical cannabinoids can relieve the symptoms associated with asthma.

What is asthma?

With this chronic respiratory disease, the airways become narrower as a result of inflammation. At the same time, the production of mucus is stimulated, so asthmatics suffer from symptoms such as shortness of breath and coughing fits. In many cases, recurrent respiratory tract infections exacerbate the disease.

The causes have not yet been clarified. However, there are several factors that can increase the risk of developing asthma. These include hereditary factors, respiratory infections or the use of certain drugs during pregnancy (such as antibiotics). Smoking tobacco and regular inhalation of harmful substances (such as sulphur dioxide) are also risk factors.

Which forms of asthma exist?

Asthma is divided into different forms. These include, among others:

  • Extrinsic bronchial asthma (allergic asthma): This form of asthma is an allergic reaction caused by one or more allergens (e.g. animal hair, house dust, pollen, food). Although these allergens are normally harmless, the immune system classifies them as harmful and reacts with an excessive pathological defence reaction.
  • Intrinsic asthma (non-allergic asthma): Here the triggers are, for example, respiratory tract infections or the regular inhalation of air pollutants such as exhaust fumes or smoking tobacco. In most cases, this chronic respiratory disease does not develop until adulthood.
  • Mixed asthma: Allergens or other stimuli can be the cause of the mixed form of allergic and non-allergic asthma from which the majority of affected adults suffer.
  • Exercise asthma: This form of asthma is widespread. Often an asthma attack occurs under physical stress. Dry or cold air can also make it easier to have an asthma attack. Children and young people are particularly affected.
  • Infectious asthma: A viral infection can cause acute or chronic inflammation of the airways. The viruses that cause this can be influenza, adenovirus or corona viruses. Infectious asthma can also affect small children. This is often caused by RS viruses (respiratory syncytial viruses), which cause cold symptoms.

What are the symptoms of asthma?

When an asthma patient comes into contact with an allergen or other trigger, the bronchial tubes swell and thick mucus is formed. This causes the airways to constrict and the breathing muscles to contract. As a result, breathing becomes difficult, especially when breathing out. Typical signs of asthma can be:

  • Coughing with or without a thick sputum
  • Accelerated breath
  • Tightness in the chest
  • A whistling or rattling noise when breathing out

These symptoms usually occur in attacks. After an attack, asthmatics are usually symptom-free. Complaints then only reappear with the next attack

Diagnosis and treatment

Various illnesses, such as pertussis, cystic fibrosis, or bronchitis, can trigger symptoms similar to those of an acute asthma attack. Therefore, a comprehensive diagnosis is particularly important. The doctor treating you will first carry out a physical examination and listen to your lungs. Further examinations such as an allergy test, a lung function test, blood tests and an X-ray of the lungs will follow.

There is no cure for asthma, so therapy aims to reduce the frequency and severity of attacks. An important pillar of therapy is to maintain the patient’s performance and lung function. Regular exercise and breathing exercises should therefore be on the patient’s agenda.

In drug treatment, bronchodilator drugs (bronchodilators) are mainly used. Short-acting beta-2 sympathomimetics (e.g. salbutamol or terbutaline) are used for acute asthma attacks. These active substances can be inhaled by the patient with the help of a spray in cases of severe breathing difficulties. In addition to this essential medication, patients are often given long-acting beta-2 sympathomimetics (e.g. formoterol or salmeterol) that work for about 12 hours.

Anti-inflammatory drugs such as corticosteroids also play an important role in long-term therapy. For example, drugs like budesonide or fluticasone can reduce swelling in the airways and mucus production. Antileukotrienes can also be used as additional therapy, as they can also have an anti-inflammatory effect.

Like any medication, asthma drugs can cause serious adverse effects. These include coughing, hoarseness, gastro-intestinal problems, sleep disturbances, restlessness, tachycardia (palpitations), arrhythmia (irregular heartbeat) and tremor.

Studies on asthma and cannabis

It was mentioned at the beginning of the article that researchers have been studying the bronchodilator effect of cannabis since the 1970s. In 1974, US researchers carried out a study in which one group of participants received the cannabinoid tetrahydrocannabinol (THC) and another group received isoproterenol (1). This showed that although the bronchodilator effect of THC was weaker, it lasted longer.

Another study showed that salbutamol had a rapid bronchodilator effect. In contrast, the effect of THC was slower (2).

Cannabinoids may have anti-inflammatory effects

The bronchial tubes of patients can also become inflamed during a period when they are not suffering from attacks (chronic inflammation). If an acute asthma attack occurs, the inflammation can get worse, so anti-inflammatory drugs can be prescribed. This is where cannabinoids derived from cannabis, especially the cannabinoid cannabidiol (CBD), could deploy an anti-inflammatory effect.

In 2015, Brazilian researchers declared that T-helper-2 lymphocytes could be detected in the lungs of asthma patients (3). These T-helper cells are responsible for the recognition of antigens and are involved in the production of cytokines. Given that the interaction of T-helper cells with antigens/allergens could play a key role in the development of inflammatory diseases, the aim of the study was to assess the anti-inflammatory potential of CBD.

Asthma was then induced in rats by ovalbumin (OVA). The animals then received 5 milligrams of CBD per kilogram of body weight. 24 hours later, the cytokines in serum levels were determined and it was found that CBD could be a potential new drug to modulate the inflammatory response in asthma.

Another study at the University of Florence in Italy focused on the involvement of cannabinoids in inflammatory processes and the interaction with endocannabinoids (4). The researchers explained that activation of cannabinoid receptor 2 (CB2) might have an anti-inflammatory effect. A bronchodilator effect could be achieved by activating cannabinoid receptor 1 (CB1). Thus, the endocannabinoid system could be a potential target for cannabis-based drugs.

Treatment with medical cannabis

Smoking medical cannabis flowers is not recommended for asthmatics. This can cause bronchitis, for example, which can make the asthmatic symptoms worse. In the context of medical cannabis treatment, vaporization/inhalation with a vaporizer or oral administration is therefore recommended.

(1) American Review of Respiratory Disease, Volume 109, 1974, Donald P. Tashkin et al,“Acute effects of smoked marijuana and oral delta-9-tetrahydrocannabinol on specific airway conductance in asthmatic subjects

(2) Williams SJ, Hartley JP, Graham JD, 1976, “Bronchodilator effect of delta1-tetrahydrocannabinol administered by aerosol of asthmatic patients

(3) Laboratoire de Pharmacologie Respiratoire, France, Grassin-Delyle S1 et al., 2014, “Cannabinoids inhibit cholinergic contraction in human airways through prejunctional CB1 receptors

(4) University of Florence, Italy, Pini A1 et al., 2012, “The role of cannabinoids in inflammatory modulation of allergic respiratory disorders, inflammatory pain and ischemic stroke