How Weed Changes the Brain: Debunking Misconceptions

Since cannabis’ legalization in Canada in 2018, the amount of questions I’ve received about its usage has skyrocketed. Typically, it's some variation of “I’ve heard weed is supposed to help with anxiety, so why does it make me feel so anxious?” or “Why did marijuana make me feel great before and not so great anymore?” These questions are good ones to be asking, especially since the research in this area has been slow to evolve. Anecdotally, some people will notice that cannabis helps with their anxiety in the moment. That means they use it when they feel stressed or anxious and then feel relaxed or distracted when high. However, cannabis has a different impact on our brains and bodies in the long term, especially when it is used regularly. To really understand the relationship between marijuana and anxiety, let’s take a look at studies that have followed participants over a long period of time.

The Relationship Between Cannabis and Anxiety

First of all, we know there is an established connection between anxiety and cannabis. Research from before legalization showed that frequent cannabis users consistently are more likely to have an anxiety disorder, and that people with an anxiety disorder are more likely to use cannabis¹. A very large study followed over 3000 young adults from birth until they were 21 years old. Those who regularly used marijuana from ages 15-21 were much more likely to experience symptoms of anxiety disorders in early adulthood². Earlier this year, a group of researchers did the heavy lifting for us and analyzed 24 different studies on cannabis use and anxiety. They came to the same conclusions: that cannabis use was significantly associated with increased likelihood of developing an anxiety condition³. This means that smoking/absorbing/vaping/eating marijuana products puts you at greater risk for developing anxiety, especially if it’s used long-term. So, what’s considered “long term usage”? Researchers have found that regular use over a period of 6 months is enough to increase anxiety symptoms⁴. If you yourself are a long-term user, you may have noticed that you experience more anxiety or paranoia when it comes to yourself, others, or your health more than you used to. Some may notice that they have more anxious thoughts; others may notice their anxiety in their body. For example, their body is quicker to shake when they are stressed, they’ve experienced panic attacks more often, or their heart races more quickly than it used to when feeling nervous. If you have experienced any of this, research tells us you’re certainly not alone in that experience.

What’s the takeaway?

By this point you might be wondering something like, “Maybe people with high anxiety are just more likely to seek out weed as a possible way to self-medicate. Just because weed users are more likely to have anxiety, doesn’t mean weed causes anxiety.”

This is true- we can’t say for sure that it causes anxiety symptoms. Following that thought then, maybe they are anxious and turning to weed in hopes that it will reduce their anxious symptoms, thoughts, or feelings. These studies show that even after long term use, anxiety symptoms are just as present (and they actually increase). So, we know that, even if people are using cannabis in the hopes that it improves their anxiety, it doesn’t seem to be working how they’d like it to. In fact, when people reduced how much cannabis they were consuming, their anxiety and depression actually reduced, too⁵.

The Highs and Lows of THC

By now, you might be wondering something like, “Ok, these are general statements. We know that there are different strains and potencies of cannabis, and you might be lumping THC and CBD together here. Does the potency make a difference?” Yes, yes it does, you informed consumer of research, you!

Up until this point, the cannabis we’ve been talking about has included some form of the psychoactive component known as THC (tetrahydrocannabinol). It’s THC that is responsible for that feeling of intoxication known as being “high.” When drug tests are testing for marijuana usage, it’s THC that they are detecting in the blood stream or urine. THC is linked to anxiety, physical and mental sedation, and psychotic symptoms like delusions⁶. Part of its link to these symptoms has to do with the fact that it triggers the release of dopamine, a neurotransmitter in our brain that is part of the reward pathway. Unfortunately, sometimes too much of a good thing can be a problem: the "dopamine hypothesis of schizophrenia" suggests that the psychotic symptoms of schizophrenia (like hearing or seeing things that aren't there) are caused from too much dopamine.

When it comes to THC and its negative effects, part of the problem is the strength or potency of the THC content. At very low doses, THC may help reduce anxiety responses by triggering a relaxing or euphoric state, but at high doses it creates problematic effects like the ones mentioned above⁷. So, what’s a high dose? Studies have found that products with THC doses of 10mg or more can increase anxiety and produce a psychotic effect, while a low dose would be considered around 1.0 to 5.0 mg of THC⁸. Part of the problem some people encounter when it comes to THC is that they keep increasing the amount they’re taking. By increasing the strength of their cannabis, they might unintentionally be causing more harm than good.

Why do people increase their THC doses?

Some people are likely to increase their THC doses because they feel they’ve developed a tolerance and no longer get the same “high.” To understand that, we turn our attention to what THC actually does to our bodies. Chemicals in cannabis bind to certain receptors in our body called cannabinoid receptors. Normally, it's our brain’s natural chemical called anandamine that will bind to these receptors, but the structure of THC is similar enough to bind to them as well. These cannabinoid receptors are found throughout our brain and nervous systems⁹. We have a lot of these receptors in our body because they play a role in motivational, emotional, and affective processing. With continued cannabis use, the body starts to reduce the amount of cannabinoid receptors available¹⁰. This “downregulation” is part of the body maintaining balance and making up for the influx of THC. To oversimplify it: over time, the build up of THC in our blood causes receptors to disappear. Cannabis at first binds to all our cannabinoid receptors, then with regular use our body starts to get rid of some of those receptors, which leads to people experiencing differences in how their minds and bodies react to cannabis. Regular cannabis users might be increasing their doses because they are trying to achieve the same type of high they once got; however, the facts are they just don’t have the same receptor sites they used to.

What’s CBD?

CBD, on the other hand, is another type of cannabinoid found in cannabis. It’s CBD that’s been shown to be safe and well-tolerated by healthy people¹¹ and it doesn’t produce the psychoactive effects that THC does. In other words, people don’t get a feeling of being “high” from CBD. Research has shown that people taking only CBD do not report feeling intoxicated¹². When studies talk about the benefits of cannabis, it’s generally CBD they’re referring to. For example, studies have found that CBD has been useful in the treatment of anxiety disorders¹³ and epilepsy¹⁴. While it’s not without its risks, it doesn’t seem to be connected to developing anxiety, delusions, or paranoia like its THC counterpart.

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Here's the "Too Long; Didn't Read" of it:

• High doses of THC (typically over 10mg) over long periods of time are linked to the development of anxiety, paranoia, hearing voices other people can't hear, and seeing things that are not really there. Lower doses (1 to 5mg) are not as likely to have negative effects.
  

• THC builds up in the blood, which shuts down some of our brain and body's receptors over time, and can lead people to experience different highs than they used to have.
  

• When people stop consuming THC, these receptors can actually come back. This means that taking a break from cannabis can help your body "undo" some of the impact THC has had on it.
  

• CBD does not cause people to feel high or intoxicated. CBD and THC are not the same thing, and it's possible to have cannabis that has a high CBD content without a high THC content.
  

• There's still a lot to be known about how and why cannabis affects the brain and body. Research is continuing to explore this area.

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References

Battistella, G., Fornari, E., Annoni, J. M., Chtioui, H., Dao, K., Fabritius, M., Favrat, B., Mall, J. F., Maeder, P., & Giroud, C. (2014). Long-term effects of cannabis on brain structure. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology, 39(9), 2041–2048. https://doi.org/10.1038/npp.2014.67

Boggs, D., Nguyen, J., Morgenson, D. et al. Clinical and Preclinical Evidence for Functional Interactions of Cannabidiol and Δ9-Tetrahydrocannabinol. Neuropsychopharmacol. 43, 142–154 (2018). https://doi.org/10.1038/npp.2017.209

Crippa, J. A., Zuardi, A. W., Martín-Santos, R., Bhattacharyya, S., Atakan, Z., Mcguire, P., & Fusar-Poli, P. (2009). Cannabis and anxiety: A critical review of the evidence. Human Psychopharmacology: Clinical and Experimental, 24(7), 515-523. doi:10.1002/hup.1048 Freeman AM, Petrilli K, Lees R, Hindocha C, Mokrysz C, Curran HV, Saunders R, Freeman TP. How does cannabidiol (CBD) influence the acute effects of delta-9-tetrahydrocannabinol (THC) in humans? A systematic review. Neurosci Biobehav Rev. 2019 Dec;107:696-712. doi: 10.1016/j.neubiorev.2019.09.036. Epub 2019 Sep 30. PMID: 31580839. Hayatbakhsh, Najman, Jamrozik, Mamun, Alati, and Bor (2007). Cannabis and Anxiety and Depression in Young Adults: A Large Prospective Study, Journal of the American Academy of Child & Adolescent Psychiatry, Volume 46, Issue 3, Pages 408-417. doi.org/10.1097/chi.0b013e31802dc54d.

Hser, Y., Mooney, L. J., Huang, D., Zhu, Y., Tomko, R. L., Mcclure, E., . . . Gray, K. M. (2017). Reductions in cannabis use are associated with improvements in anxiety, depression, and sleep quality, but not quality of life. Journal of Substance Abuse Treatment, 81, 53-58. doi:10.1016/j.jsat.2017.07.012

Mammen, G., Rueda, S., Roerecke, M., Bonato, S., Lev-Ran, S., & Rehm, J. (2018). Association of Cannabis With Long-Term Clinical Symptoms in Anxiety and Mood Disorders. The Journal of Clinical Psychiatry, 79(4). doi:10.4088/jcp.17r11839

Raymundi, A.M., da Silva, T.R., Sohn, J.M.B. et al. Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies. BMC Psychiatry 20, 420 (2020). https://doi.org/10.1186/s12888-020-02813-8

Skelley, J. W., Deas, C. M., Curren, Z., & Ennis, J. (2020). Use of cannabidiol in anxiety and anxiety-related disorders. Journal of the American Pharmacists Association, 60(1), 253-261. doi:10.1016/j.japh.2019.11.008

Stott, C. G., Nichol, K., Jones, N. A., Gray, R. A., Bazelot, M., & Whalley, B. J. (2019). The Proposed Multimodal Mechanism of Action of Cannabidiol (CBD) in Epilepsy: Modulation of Intracellular Calcium and Adenosine-mediated Signalling. Epilepsy & Behavior, 101, 106734. doi:10.1016/j.yebeh.2019.08.009

Xue, S., Husain, M. I., Zhao, H., & Ravindran, A. V. (2020). Cannabis Use and Prospective Long-Term Association with Anxiety: A Systematic Review and Meta-Analysis of Longitudinal Studies. The Canadian Journal of Psychiatry, 070674372095225. doi:10.1177/0706743720952251

Chasing Masculinity: Why It Hurts Sometimes

In my work, I have regularly come across young men trying to counter feelings of personal failure with attempts at (and these quotes are their words, not mine) “becoming alpha,” “building swag,” and “gaining clout.” You may have guessed (correctly) that I work with young adults. By this, they often mean that they are trying to embody that elusive image of masculinity. You can probably conjure up an idea of what that image looks like: it involves suppressing emotion, solving problems without help, being successful, and acting aggressively if needed (Jansz, 2000). Despite that initial hope many young men have that those qualities will help them, we know from the research that trying to conform to traditional male gender roles is actually related to more psychological distress (Hayes & Mahalik, 2000; Houle, Mashara, & Chagnon, 2008; Liu, Rochlen, & Mohr, 2005; Moller-Leimkuhler, 2003). Men who try to force themselves to stick to traditional gender roles are more likely to be reluctant to seek help and to struggle with expressing emotion, which can lead to difficulty admitting when they are in distress (Moller-Leimkuhler, 2003). In other words, they may not know how to talk about what’s going on for them, so they bottle up their emotions and suffer silently. Because of this reluctance to seek help and lean on the people in their lives, trying to conform to a traditional male gender role can increase the risk of suicidal behaviour (Houle, Mashara, & Chagnon, 2008). When we consider the research, we see that young men often experience a gender-specific pressure to conform to traditional masculinity, and that pressure can cause stress, worry, confusion, and misery.

The important takeaway is not that masculinity is harmful, but rather it can be harmful to mental health if someone is struggling silently for fear of appearing less masculine to others

The important takeaway is not that masculinity is harmful, but rather it can be harmful to mental health if someone is struggling silently for fear of appearing less masculine to others. Perhaps surprisingly to many people, research shows that men with high self-compassion are actually better able to adhere to masculine norms without internalizing shame or self-criticism for engaging in behaviours they view as less masculine (Health et al, 2017). In other words, when a man is self-compassionate, he is less concerned with whether self-compassion is considered masculine or not. He is more accepting of help when he needs it and acknowledges that mistakes and feelings of failure are a part of life, and understands that admitting either of these things does not legitimately threaten his masculinity. These qualities help him lead a healthy and balanced life. Luckily, self-compassion is a skill that can be developed through time, effort, and practice.

When a man is self-compassionate, he is less concerned with whether self-compassion is considered masculine or not. He is more accepting of help when he needs it and acknowledges that mistakes and feelings of failure are a part of life, and understands that admitting either of these things does not legitimately threaten his masculinity.

Building up self-compassion is one way of strengthening ourselves against the onslaught of external pressures that threaten our mental health. Self-compassion refers to viewing both positive and negative experiences as opportunities for growth and learning. It involves relating to yourself in a kinder way, understanding that failure and setbacks are a part of life, and recognizing your feelings and where they’re coming from. Self-compassion is a buildable skill that has been shown to improve mental health (Neff, Kirkpatrick, & Rude, 2007; Neff & McGehee, 2010) and help with motivation for our goals (Sirois, Kitner, & Hirsch, 2015). Part of the reason self-compassion is helpful to mental health is because it helps us become more self-accepting and view our weaknesses with less harsh criticism (Neff, Kirkpatrick, & Rude, 2007). When we are self-compassionate, we acknowledge our weaknesses but instead of trying to hide them away, we actively seek to learn from them or improve them because that's what will be helpful to us.

On that note, here’s a question I often hear about self-compassion: “I don’t want to accept myself. If I accept my mistakes, doesn’t that mean that I’m just being complacent and letting myself off easy? How do I improve myself if I just accept myself how I am?” First, it’s important to realize that this is a misconception. Self-compassion isn’t about letting yourself off easy, sometimes it’s actually about doing the more difficult thing because you know it’s better for you. Self-compassion is about acknowledging where you went wrong and committing to improvement for the future. Some people misguidedly assume that self-criticism will be the motivation they need to do better, but let’s look at an example. Imagine you’ve been planning on feeling healthier but get tempted by the donut in the lunchroom. If you beat yourself up for that decision and think to yourself “I’m useless. I don’t stick to any of my plans. I just ruined everything.” it’s likely that you’ve started down a self-critical spiral. Those self-critical thoughts lead to a depressed mood, and there goes your motivation to eat healthy for the rest of the day. Now imagine instead you try to take a self-compassionate approach. You think to yourself, “I regret that choice, but it happens. It’s not a big deal. I won’t lose all my progress if I just keep things balanced and make healthier choices the rest of the day.” That self-compassionate attitude may be enough to stop your motivation from crashing. Ideally, that attitude can carry on the next day, when you know the self-compassionate thing to do is to resist the unhealthy snacks because, as good as it would taste in the moment, you know it would upset you based on the health goals you’ve set for yourself. The self-compassionate thing isn’t the easy thing, it’s the what’s best for you thing.

"I’ve basically been taught not to share my feelings, so it makes sense that a lot of the time I feel like I can’t reach out to other people. It’s okay that I feel uncomfortable with the idea of talking to a friend about what I’m dealing with, in fact a lot of people feel the same way I do. At the same time, I know talking to people helps, and I know I deserve that help."

Let’s circle back to self-compassion and that gender-specific pressure to conform to traditional masculinity. So, what does self-compassion sound like for someone who is struggling with these issues? It could sound like “I’ve basically been taught not to share my feelings, so it makes sense that a lot of the time I feel like I can’t reach out to other people. It’s okay that I feel uncomfortable with the idea of talking to a friend about what I’m dealing with, in fact a lot of people feel the same way I do. At the same time, I know talking to people helps, and I know I deserve that help.” Self-compassion could look like texting that friend, calling that help line, or booking that counselling session. There’s hundreds of examples of what self-compassion could sound like or look like. And hey, if you think that could never and will never be you, let me tell you that reading an article on ways of showing yourself self-compassion is you being self-compassionate. References Hayes, J. A., & Mahalik, J. R. (2000). Gender role conflict and psychological distress in male counseling center clients. Psychology of Men & Masculinity, 1, 116-125. doi:10.1037/1524-9220.1.2.116 Heath, P. J., Brenner, R. E., Vogel, D. L., Lannin, D. G., & Strass, H. A. (2017). Masculinity and barriers to seeking counseling: the buffering role of self-compassion. Journal of Counseling Psychology, 64, 94-103. doi: 10.1037/cou0000185

Houle, J., Mashara, B. L., & Chagnon, F. (2008). An empirical test of a mediation model of the impact of the traditional male gender role on suicide behavior in men. Journal of Affective Disorders, 107, 37-43. doi: 10.1016/j.jad.2007.07.016

Liu, W. M., Rochlen, A., & Mohr, J. J. (2005). Real and ideal gender-role conflict: Exploring psychological distress among men. Psychology of Men & Masculinity, 6, 137-148. doi:10.1037/1524-9220.6.2.137 Möller-Leimkühler, A. M. (2003). The gender gap in suicide and premature death: Why are men so vulnerable? European Archives of Psychiatry & Clinical Neuroscience, 253, 1-8. doi:10.1007/s00406-003-0397-6 Neff, K. D., Kirkpatrick, K. L., & Rude, S. S. (2007). Self-compassion and adaptive psychological functioning. Journal of Research in Personality, 4, 139-154. doi: 10.1016/j.jrp.2006.03.004

Neff, K. D., & McGehee, P. (2010). Self-compassion and psychological resilience among adolescents and young adults. Self & Identity, 9, 225-240. doi: 10.1080/15298860902979307 Sirois, F., Kitner, R., & Hirsch, J. (2015). Self-compassion, affect, and health-promoting behaviors. Health Psychology, 34, 661-669. doi: 10.1037/hea0000158

Take a SHALLOW breath: can we improve asthma through breathwork?

Could we be breathing better? All of us are familiar with the idea of taking a deep breath. We’re told to do it when stressed, anxious, angry, or overwhelmed. I have even written a previous blog post about the science behind deep breathing and the mechanisms by which it helps calm the body (spoiler: it’s the extended exhale that matters, not the inhale). Much more rarely, however, have we been told to take a shallow breath. A number of research studies out there seem to be highlighting the benefits of shallow nasal breathing, so let’s delve into the research for a more comprehensive understanding.

Why is Nasal Breathing Better?

The Short:

Our bodies are built to breathe through our noses, and the production of nitric oxide is stimulated when we inhale and exhale through our nose.

The Simple: Unlike the mouth, breathing through the nose filters, humidifies, and warms air. When we breathe through our nose, we are helping clear our air pathways of dust, allergens, and bacteria. That’s why breathing through our nose instead of our mouth is the first defense against infections like covid19. If that wasn’t enough to make you think twice about your breathing, mouth breathing is also associated with more throat infections and cases of gingivitis¹.

The Science: Nitric oxide plays a key role in the beneficial effects that come from nasal breathing. It is produced in our paranasal sinuses and its production is stimulated by nasal breathing. When we breathe through our nose, our nose produces nitric oxide. The people that breathe through their mouth have been shown to have less nitric oxide in their airways². Here’s why nitric oxide is important: it stimulates mucus secretion which increases removal of dust and viral particles from our airways, it produces antimicrobial effects against bacteria and viruses, and it can actually help inactivate viruses by modifying their ability to reproduce³. Nitric oxide also helps to deliver more oxygen to tissues in our body, so when we are breathing through our noses, we are actually helping send oxygen to faraway tissues in our body.

Why are “Mouth Breathers” so common right now?

The prolonged use of face masks during the covid-19 pandemic may actually be responsible for converting some of us from nose breathers to mouth breathers. Studies have noted wearing facemasks can actually alter our normal breathing pattern⁴ ⁵. That said, there’s not enough research out there on this topic. It remains uncertain how many of us are actually mouth breathers, though pre-pandemic studies have reported numbers like 26% to 56% ⁶ ⁷ and there is a chance that it's higher following long term mask usage. Most of the studies that look at mouth breathing focus on children populations and state potential causes of mouth breathing to be adenoid issues, thumb sucking, chronic allergies, deviated nasal septums, excessive pacifier use, and nasal polyps ⁸. There just isn’t enough research out there on adult populations to draw any sort of conclusion as to why mouth breathing continues into adulthood, but regardless, we know it happens.

Does Nasal Breathing Improve Asthma?

An association between asthma and mouth breathing has been shown in the research with children, adolescents, and adults⁹, but there’s not enough evidence out there to clearly understand the link between them. That said, there has been research about improving asthma by switching from mouth breathing to nasal breathing, so we can see that the way we breathe has an important role in asthma.

One study found that shallow nasal breathing led people to use their inhalers less, and that using their inhaler less did not make their asthma worse¹⁰.

shallow nasal breathing led people to use their inhalers less, and using their inhaler less did not make their asthma worse¹⁰.

So in other words, nasal breathing helped people use their inhalers less and their asthma did not get worse from not using their inhaler regularly. The tricky part: Even though they were using their inhaler less, it wasn’t because their airways improved or their lung inflammation went down. There wasn’t a physiological improvement due to the breathing exercises. The researchers suggest that maybe participants were using their inhalers less because they didn’t need to inhale their full dose of corticosteroids anyway to manage their asthma, and that a lower dose is all that would be required to help their asthmatic needs. Either way, nasal breathing seems to have made people feel that their asthma is more manageable.

A study in 2008 took a different approach: it researched whether forced mouth breathing would decrease lung function in people with mild asthma. Lung function actually did decrease over time on days where participants were mouth breathing, and coughing and wheezing were more likely to happen, too¹¹.

Buteyko Breathing Method (AKA slow and shallow breathing)

The Buteyko method is a form of nasal breathing that is based on the premise that slow and shallow nose breathing improves asthma by inducing hypoventilation and raising blood carbon dioxide levels¹². Buteyko breathing makes use of control pause exercises and breath holding exercises to improve breathing. The idea behind it is that asthma is related to hyperventilation that causes chest tightening (bronchospasm) and mucus build up (accumulation of secretion). The goal of Buteyko breathing then is to improve these two things by normalizing blood carbon dioxide levels through smaller inhalation and exhalations (called reduced-volume breathing).

Here’s an example of a control pause exercise that’s used in Buteyko breathing to evaluate breathing health. The below exercise is adapted from a study at Mansura University¹³.

​1. Sit upright with good posture.

2. Take a small breath in (2 s) and a small breath out (3 s). Hold nose after the “out” breath, with empty lungs but not too empty.

​3. Count how many seconds you comfortably last before the need to breathe in again.

4. Release the nose and breathe in through it. This breath should be no greater than the breath prior to taking measurement. Pausing too long could cause you to take too big of a breath after the measurement.

Here’s an example of a breath holding exercise that’s used in Buteyko breathing, adapted from the same study.

1. Place a finger under your nose, just above your top lip, close enough to your nostril that you can feel airflow.

2. Breathe air slightly into tip of the nostril. Imagine the finger is a feather that you don’t want to move when you exhale.

3. The more warm air you can feel, the bigger you are breathing. Concentrate on calming your breath to reduce the amount of warm air on your finger.

4. Maintain this shallow nasal breathing for 4 minutes.

Here’s how you’d put them together, adapted from the same study.

1. Reduce breathing for 4 min. Wait 2 min and take Control pause. Reduce breathing for 4 min. Wait 2 min and take Control pause.

The Mansura University study found that these Buteyko breathing exercises (practiced daily for four weeks) improved asthmatic symptoms, peak expiratory flow rate, and improved performance on a pulmonary function test. Another study found that a group of participants who had been trained in Buteyko breathing saw an 85% reduction in rescue inhaler use and a 50% reduction in regular inhaled steroid use even at 6 month follow up¹⁴.

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Here's the "Too Long; Didn't Read" of it:

• Nasal breathing filters, humidifies, and warms air. It clears our air pathways of dust, allergens, and bacteria and sends oxygen to tissue in our body. Mouth breathing does NOT have these positive effects.
  

• We can become better nasal breathers through practice.
  

• Nasal breathing improves asthma and sleep quality.
  

• The Buteyko Breathing method has been shown to significantly improve scores on lung function tests, decrease asthmatic symptoms, and improve physical performance.
  

• More studies in this area are needed, but for now the outcomes look promising.

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References

Abreu, R. R., Rocha, R. L., Lamounier, J. A., & Guerra, Â. F. M. (2008). Prevalence of mouth breathing among children. Jornal de Pediatria, 84, 467-470.

Akturk, E. S., Aydin, I., & Seker, E. D. (2022). The effects of mask usage during the COVID-19 pandemic on temporomandibular joint. Clinical Oral Investigations: preprint.

Araújo, B. C. L., de Magalhães Simões, S., de Gois-Santos, V. T., & Martins-Filho, P. R. S. (2020). Association between mouth breathing and asthma: a systematic review and meta-analysis. Current Allergy and Asthma Reports, 20(7), 1-10.

Bruton, A., & Thomas, M. (2011). The role of breathing training in asthma management. Current opinion in allergy and clinical immunology, 11(1), 53-57.

Fricker, J., Kharbanda, O. P., & Dando, J. (2013). Orthodontic diagnosis and treatment in the mixed dentition. In Handbook of Pediatric Dentistry (pp. 409-445).

Hallani, M., Wheatley, J. R., & Amis, T. C. (2008). Enforced mouth breathing decreases lung function in mild asthmatics. Respirology, 13(4), 553-558.

Martel J, Ko YF, Young JD, Ojcius DM. Could nasal nitric oxide help to mitigate the severity of COVID-19? Microbes Infect. 2020 May-Jun;22(4-5):168-171. doi: 10.1016/j.micinf.2020.05.002.

Martins, D. L. L., Lima, L. F. S. C., de Farias Sales, V. S., Demeda, V. F., da Silva, A. L. O., de Oliveira, Â. R. S., & Lima, S. B. F. (2014). The mouth breathing syndrome: prevalence, causes, consequences and treatments. A literature review. Journal of Surgical and Clinical Research, 5(1), 47-55.

McHugh, P., Aitcheson, F., Duncan, B., & Houghton, F. (2003). Buteyko Breathing Technique for asthma: an effective intervention. Journal of the New Zealand Medical Association.

Mohamed, E. M. H., ELmetwaly, A. A. M., & Ibrahim, A. M. (2018). Buteyko breathing technique: a golden cure for asthma. American Journal of Nursing, 6(6), 616-624.

Opat, A. J., Cohen, M. M., Bailey, M. J., & Abramson, M. J. (2000). A clinical trial of the Buteyko breathing technique in asthma as taught by a video. Journal of Asthma, 37(7), 557-564.

Slader, C. A., Reddel, H. K., Spencer, L. M., Belousova, E. G., Armour, C. L., Bosnic-Anticevich, S. Z., ... & Jenkins, C. R. (2006). Double blind randomised controlled trial of two different breathing techniques in the management of asthma. Thorax, 61(8), 651-656.

Törnberg, D. C. F., Marteus, H., Schedin, U., Alving, K., Lundberg, J. O. N., & Weitzberg, E. (2002). Nasal and oral contribution to inhaled and exhaled nitric oxide: a study in tracheotomized patients. European Respiratory Journal, 19(5), 859-864.

Triana, B. E. G., Ali, A. H., & León, I. G. (2016). Mouth breathing and its relationship to some oral and medical conditions: physiopathological mechanisms involved. Revista Habanera de Ciencias Médicas, 15(2), 200-212.

Verma, S. Mouth Mask: A Blessing Or A Curse For Oral Health. Journal of Prosthodontics Dentistry.