Feeling anxious about your upcoming exam? Stressed about all the assignments you have yet to complete? Chances are that all of us have experienced the feeling of anxiety at some point in our lives. Anxiety is known to be accompanied by excessive fear and extreme worry, both of which interfere with one’s daily life, causing distress (Duval, Javanbakht and Liberzon, 2015). Anxiety disorders, specifically, affect about 12% of all adults in Canada (Diane, 2018), while their lifetime prevalence extends to about 28% of the world’s population (Duval, Javanbakht and Liberzon, 2015). Since anxiety and anxiety disorders have become so common in our modern society, it is intriguing that we do not have a better understanding of the neurobiological mechanisms and circuitry that lead to their presence.
To best understand the suggested pathway with which anxiety is produced, it is important that we grasp the diversity of structures in the nervous system that contribute to feelings of anxiety. In general, anxiety disorders are the result of hyperactivation in the emotion-generating (limbic) and regulatory (prefrontal cortex) regions of the brain (see Figure 1) (Martin et al., 2009; Duval, Javanbakht and Liberzon, 2015). The most abundantly studied, and arguably crucial, structure in these regions, however, is the amygdala, which is part of the limbic system and is found in the medial temporal lobe (see Figure 2) (Martin et al., 2009). The amygdala processes emotion based on external stimuli to generate behavioural responses (Martin et al., 2009). Its increased size and activity are believed to contribute to its anxiolytic effects (Patriquin and Mathew, 2017).
Recent studies by researcher Bo Li and colleagues in 2018, at Cold Spring Harbour Laboratory, have led to the discovery of a potential neural circuit in the amygdala that may produce the majority of anxiolytic effects. From previous studies, Li knew that two main portions of the amygdala were involved in coordination of responses to threatening stimuli: (1) the central amygdala and (2) the bed nucleus of the stria terminalis (BNST) (see Figure 2) (Li, 2018). Through experimentation on mice, he was able to determine the underlying circuitry of these regions that control feelings of anxiety. He found that the increased stimulation of neurons expressing a molecule known as somatostatin (SOM) in the central amygdala of individuals with anxiety, was positively correlated with the release of dynorphin, an endocrine hormone (Li, 2018). Dynorphin interferes with the normal regulatory mechanisms of the SOM neurons in the BNST causing overexcitation and leading to anxious behaviour (Li, 2018).
Knowledge of this circuitry is essential to the discovery of new and effective treatments for anxiety disorders. For example, it is now known that an effective way to target anxiety therapeutically may be to rationally design a drug that is an antagonist of dynorphin, reducing BNST overexcitation (Li, 2018). In future studies, it would be beneficial to consult medicinal chemists in hopes of designing new and effective drugs that may have this inhibitory effect, through competitively inhibiting the docking of dynorphin to its receptors, which have yet to be found (Li, 2018).
References
Biorender, 2018. Biorender. Available at: <https://app.biorender.io/illustrations/edit/5bf0be17472d200012a9bfc8> [Accessed 17 Nov. 2018].
Diana, 2018. Statistics Canada releases mental health survey results. [online] mindyourmind. Available at: <https://mindyourmind.ca/blog/statistics-canada-releases-mental-health-survey-results> [Accessed 24 Nov. 2018].
Duval, E.R., Javanbakht, A. and Liberzon, I., 2015. Neural circuits in anxiety and stress disorders: a focused review. Therapeutics and Clinical Risk Management, [online] 11, pp.115–126. Available at: <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4315464/> [Accessed 18 Nov. 2018].
Li, B., 2018. Researchers Find Brain Circuit That Drives Anxiety. [online] Brain & Behavior Research Foundation. Available at: <https://www.bbrfoundation.org/content/researchers-find-brain-circuit-drives-anxiety> [Accessed 18 Nov. 2018].
Martin, E.I., Ressler, K.J., Binder, E. and Nemeroff, C.B., 2009. The Neurobiology of Anxiety Disorders: Brain Imaging, Genetics, and Psychoneuroendocrinology. Psychiatric Clinics of North America, [online] 32(2), pp.549–575. Available at: <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3684250/> [Accessed 18 Nov. 2018].
Patriquin, M.A. and Mathew, S.J., 2017. The Neurobiological Mechanisms of Generalized Anxiety Disorder and Chronic Stress. Chronic Stress, [online] 1. Available at: <https://doi.org/10.1177/2470547017703993> [Accessed 18 Nov. 2018].
Comments
9 Responses to “Anxiety from the Neurobiological Perspective”
Hi everyone!
I decided to try and combine neuroscience and drug discovery to look at the neurological pathways that are associated with anxiety and how understanding these circuits can help us develop better treatments for anxiety disorders.
I hope you all enjoy (and if anybody has a better idea for a title please let me know)!
Maggie
Hi Maggie 🙂
This was a very interesting blog post, and I felt that you communicated the information in a way that was easy to understand, while also very detailed. The use of figures was also very helpful, and I like how you extended your research to possible methods for anxiety treatments.
I just have a couple suggestions:
1. The last sentence of the first paragraph could be re-worded to make it a bit more clear.
2. In the first sentence of the second paragraph, “with which” should be “in which”.
I hope this helps a bit and thanks for a great read!
Brittany
Hi Brittany,
Thank you so much for your suggestions! I altered the last sentence of my first paragraph a little bit, so I hope that it is slightly more clear now. I think, however, that in the first sentence of my second paragraph I correctly used “with which” instead of “in which”, as I am referring to a pathway that is used to generate anxiety, not a pathway found in anxiety.
Thanks again,
Maggie
Hi Maggie,
Fantastic blog post. I really enjoyed learning about why I get anxious. I just have a few suggestions.
1) In your first paragraph, you use a quotation. I think it would be better to paraphrase the quotation rather than quoting it directly.
2) In your first paragraph, you use lead but I think you meant led.
3) In the first sentence of your second paragraph, you use understand twice. I think that one of them should be switched with a synonym.
4) In the last sentence of your 2nd paragraph, you write “It’s increased size…” when I think you meant its increased size.
Overall great work!!!
– Abby
Hi Abby,
Thank you so much for reading and commenting on my post. I removed the quotation and reworded that part to make it flow a little bit better. I do, however, this that I correctly used the word “lead’ in my first paragraph as I meant for this to present tense, not past tense. Thank you for point out my repetition of the word “understand” I replaced one of them so that it doesn’t sound so repetitive. I also fixed the last sentence of my second paragraph.
Thank you!
Maggie
Maggie,
This was a very well-done blog post! I have a few minor suggestions that you could take into account when editing if you think they would enhance your post!
1. In your second paragraph you write “The amygdala processes emotion based on external stimuli, to generate behavioural responses.” I believe you can remove the comma in this case.
2. Your final paragraph reads “For example, it is now known that an effective way of targeting anxiety therapeutically, at its source, may be to rationally design a drug that is an antagonist to dynorphin, reducing the BNST overexcitation that causes anxiety.”This sentence seems a bit long- you could reword this to say “For example, an effective way to target anxiety at its source may be to rationally design a drug that is an antagonist to dynorphin, reducing BNST overexcitation.”
3. In your introductory paragraph, you may want to spend a sentence or two differentiating specifically between feelings of anxiety and anxiety disorders, as this in an important distinction. You open your post by writing about stress over exams and assignments and by defining anxiety, and then jump into talking about anxiety disorders. If you had word count available to you, you could add a phrase talking about what specifically an anxiety disorder is defined as, instead of just going from talking about anxiety to anxiety disorders without that context.
Overall, this was an awesome post and all of your ideas were clear! Happy editing!
Caitlin
Hi Caitlin,
Thank you so much for your suggestions! I fixed the two sentence structure suggestions that you had and tried to make it a little bit more clear in the introductory paragraph that feelings of anxiety and anxiety disorders are not the same thing, as this is very important as you pointed out.
Maggie
Hi Maggie,
Great blog post! Your discussion of the mechanisms behind anxiety was well-rounded and well-written. Nice use of Biorender, as well. There are a few suggestions you may want to take into consideration for further improvement:
– If you have space, it would helpful to include an additional pathway by which it is believed anxious behaviour is produced, or alternatively, a pathway that we currently don’t have a well-developed understanding of (you state that we don’t have a good understanding of the neurology behind anxiety in the first paragraph, but don’t expand on the idea)
– there are a few minor grammatical errors, as previous commentors have mentioned. Additionally, the last two sentences can be condensed to avoid repetition of the same concept of BNST inhibition, and for improved comprehensibility. One of the entries in your reference list is also incorrectly alphabetized.
– You make use of some good resources. Keep in mind that when you note an author directly in your content, you don’t need to follow-up with a bracketed in-text citation. Instead, for example: “. . . researcher Bo Li, PhD, and colleagues (2018) at Cold Spring . . .” (on a side note, I don’t think the ‘PhD’ is particularly important to mention, for the sake of a sentence with improved flow)
Overall, great blog post!
Hi Taylor,
Thank you for your great suggestions! I fixed the grammatical errors that were mentioned, among others, and also looked over my reference list to ensure the references are in the proper order. I, also, tried to condense my last two sentences, as you suggested, to reduce repetition and fixed the in-text citation that you mentioned. While I would love to include another mechanism through which anxiety is produced, however, I don’t think that this will be possible, as not only do I not have the space, but the pathways of anxiety are actually so poorly understood that in my research I actually could not find any other proposed mechanisms, despite trying.
Thanks again,
Maggie