I've always been skeptical of probiotic supplements in general mostly because they are stored/shipped in unrefrigerated environments. I believe in most cases the bacteria would end up dead before you even ingested it. However, some companies have developed strains that can withstand some amount of heat. But you never know where they've been stored/for how long/etc.

I remember speaking to someone who had the suggestion to try fermenting food with probiotic supplements, as that would be the only realistic way to know if they were still alive.

There are vendors that do sell probiotic supplements that come shipped in dry ice that people with Crohn's disease & other GI ailments. I don't remember the name of the company that sold them though.

But, I agree that yogurt or saurkraut/kimchi and other fermented products would be a good way to get some gut bacteria. Those would be great to use after you came off antibiotics, but it wouldn't necessarily help with genital mental health/anxiety (as far as I'm aware).

Interestingly, yeast has neurotransmitters and neurotransmitter precursors in it such as tryptophan and serotonin. [1]

Having said all that, I decided to look up the "mood enhancing" probiotic strains I've seen being sold in OTC supplements. The two strains I see are Lactobacillus helveticus Rosell-52 and Bifidobacterium longum Rosell-175 (there may be others I'm unaware of). The studies are quite small, unfortunately. (I didn't read all of them though) [2] [3] [4] [5].

Finally, this is quite a unique term I haven't come across: Psychobiotics!

Psychobiotics are probiotics that have the characteristics of modulating central nervous system (CNS) functions or reconciled actions by the gut–brain axis (GBA) through neural, humoral and metabolic pathways to improve gastrointestinal activity as well as anxiolytic and even antidepressant abilities. [6]

[1] Melatonin and Other Tryptophan Metabolites Produced by Yeasts: Implications in Cardiovascular and Neurodegenerative Diseases https://pmc.ncbi.nlm.nih.gov/articles/PMC4718080/

[2] Assessment of psychotropic-like properties of a probiotic formulation (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175) in rats and human subjects https://pubmed.ncbi.nlm.nih.gov/20974015/

[3] Probiotics Promising for Mild to Moderate Depression https://www.medscape.com/viewarticle/881877

[4] The effect of Lactobacillus helveticus fermented milk on sleep and health perception in elderly subjects https://pubmed.ncbi.nlm.nih.gov/17851460/

[5] One Giant Leap from Mouse to Man: The Microbiota–Gut–Brain Axis in Mood Disorders and Translational Challenges Moving towards Human Clinical Trials https://pmc.ncbi.nlm.nih.gov/articles/PMC8840472/

[6] Exploring the Potential of Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 as Promising Psychobiotics Using SHIME https://pmc.ncbi.nlm.nih.gov/articles/PMC10056475/