10-Minute Neuroscience: Depression

In this video, I discuss the neuroscience of depression. First, I cover the serotonin hypothesis, which suggests depression is caused by low levels of serotonin in the brain, and I explain why this hypothesis does not fully explain what’s happening in the brain to cause depression. Then, I cover several other hypotheses, including those that focus on dysregulation in the HPA axis, immune system dysfunction, and impaired neuroplasticity and neurogenesis (linked to low levels of BDNF). Along the way, I also explain the mechanisms behind some common antidepressants, such as SSRIs.

Key points:

00:00 Introduction
1:01 Serotonin hypothesis
3:48 Flaws with serotonin hypothesis
4:57 HPA axis dysregulation
6:19 Immune system dysfunction
7:30 Neuroplasticity, neurogenesis, and BDNF

REFERENCES:

Krishnan V, Nestler EJ. The molecular neurobiology of depression. Nature. 2008 Oct 16;455(7215):894-902. doi: 10.1038/nature07455. PMID: 18923511; PMCID: PMC2721780.

López-Muñoz F, Alamo C. Monoaminergic neurotransmission: the history of the discovery of antidepressants from 1950s until today. Curr Pharm Des. 2009;15(14):1563-86. doi: 10.2174/138161209788168001. PMID: 19442174.

López-Muñoz F, Alamo C, Juckel G, Assion HJ. Half a century of antidepressant drugs: on the clinical introduction of monoamine oxidase inhibitors, tricyclics, and tetracyclics. Part I: monoamine oxidase inhibitors. J Clin Psychopharmacol. 2007 Dec;27(6):555-9. doi: 10.1097/jcp.0b013e3181bb617. PMID: 18004120.

Moncrieff J, Cooper RE, Stockmann T, Amendola S, Hengartner MP, Horowitz MA. The serotonin theory of depression: a systematic umbrella review of the evidence. Mol Psychiatry. 2023 Aug;28(8):3243-3256. doi: 10.1038/s41380-022-01661-0. Epub 2022 Jul 20. PMID: 35854107; PMCID: PMC10618090.

Otte C, Gold SM, Penninx BW, Pariante CM, Etkin A, Fava M, Mohr DC, Schatzberg AF. Major depressive disorder. Nat Rev Dis Primers. 2016 Sep 15;2:16065. doi: 10.1038/nrdp.2016.65. PMID: 27629598.

[Psychx_]

It's awesome that you talked about different models! Most people only know about the serotonin/monoamine hypothesis.

[danre]

Thank-you for going beyond the serotonin hypothesis. This is my favourite video you have made so far!

[newmoonrain]

Your channel is one of my favorites; so many other science videos irritate me or go too fast or "dumb down" the information. You explain things well too.

If you haven't touched on this subject, I'd be really interested to see a video on the neuroscience hypotheses of bipolar disorder and its treatments, and how the dopamine hypothesis compares in other disorders that involve that neurotransmitter. My BD diagnosis is what got me fascinated by neuroscience and psychopharmacology to figure out what's going on in my brain and how my medications work.

Either way, your videos have been helping me so much and I'm sure they help a ton of others! Great content.

[maggiethompson]

Where do emotions play a role in these depression models - grief, loss of a dream, feeling like you don't belong, not feeling enough - when you change those thoughts, self-talk or situations, depression improves

[HandleTaken]

I suffer from depression and have for over 16 years with mixed results of treatment. For a long time, doctors were under the impression that I had Bipolar, despite never having the presence of a manic episode. I would go from “normal” (my baseline is pretty low anyway) to extreme depression, sometimes without warning.

During my “normal” periods in-between episodes (when I’m not absolutely hating my depression) I find it absolutely fascinating how the brain works. I sometimes wonder if my depression is a maladaptive survival mechanism that was carried over from childhood, given some evidence I’ve been provided that suggests it may have been present even then but not entirely understood at the time.

I only mention all of this because your presentation on HPA Axis dysregulation was particularly intriguing. I am presently in an episode (I am being treated), and I found myself asking, after going through various treatment types (talk therapy, SSRI, bolster meds, etc.) what could be triggering these sudden, extreme episodes. Stress was something that came to mind, as I am often a sufferer of chronic stress, but the note that this is already a theory out there makes me feel slightly more well-equipped to have a meaningful conversation with my doctor.

This is great content! Keep up the good work!

[blobofdespair]

Concise and easily digestible. Love this channel!

[TerryHofman]

Thanks for making this subject a little easier to understand. 👍😊

[AlexandriaNorth-fg]

I'm in CRNA school right now and your videos are a godsend. Thank you so much.

[Zen-noMyo-]

Thank you again. Very insightful overview. Time to open up my textbooks! ⚡️🧠

[jayfijan]

I love the neurogenesis hypothesis! In my neurobiology of behaviour class we talked about the possible impact irisin can have on BDNF levels and that was such a cool theory to learn about.

[hannah__]

One of the best videos there is on this topic! Very well put :)

[PriandSamiChiriac]

what about the guts? the intestines? Ive had depression twice and found out i am actually lactose intolerant, and had very low levels of vitamin D and B12. the first time i treated with medication (cause the doctor didnt ask for exames), the serotonnine ones, and it helped for some time but not quite.. the second, after I found out about the low levels, I had 4 B12 shots and started taking vitamin D, and i was a totally different person! Ive just watched a documentary about the guts and how they see it now as a second brain.. maybe you could talk a bit about it too?

[clarasava]

Can you make a video about Bipolar Disorder?

[makalefitzgerald]

Well explained and easy to follow. Thank you!

[AhmadKawaArif]

I have a question which is how these serotonin neurotransmitters build up all together eventually to bring back love feeling ?? Why it takes 4-6 weeks to build up the result ??

[margueriteoreilly]

Please Reel your work
On Social media
I do believe reaching ordinary people like myself is so important
Thank you so much
Belfast Ireland 🇮🇪 😎

[jasnithanisthar]

My baby head is dropping sometimes ... I did a MRI scan and eeg ... but the result is normal ... Can u please tell why this happen...

[DoctorJammer]

Spent a bunch of money the stickers. Lol. They're neat.

[MargotHypnos]

I am very depressed and this came up on my feed. Please help me!. I have found ECT works the best, but I cannot get access to it. The Australian Health Care system sucks.

[wubwub]

I love all your videos but I prefer those videos where you have visually represented the concept in more depth while explaining it. This is just my personal preference, since my brain is rather dependent on visualization in order to completely learn the new concept. Lectures are usually also hard for me because the lecturer often just talks but doesn't really 'show' what they are talking about.