One of the ways that Prozac helps people is by increasing allopregnanolone in the brain [1]. This is a well-known effect of Prozac, and perhaps the other SSRI's. Allopregnanolone "is a neurosteroid and acts as a positive allosteric modulator of the GABA-A receptor, the major biological target of the inhibitory neurotransmitter γ-aminobutyric acid (GABA)" [0]. GABA -> relaxation [2]. GABA supplements don't work very well on account of the blood brain barrier...

An evil pharma company recently got their version of allopregnanolone approved to treat postpartum depression. Cost of treatment: $34,000. It's cheaper to go upstream: progesterone, pregnenolone, or figure out why the body is having trouble making pregnenolone from cholesterol... Vitamin A? Thyroid?

One theory of why women experience postpartum depression is that their progesterone levels "fall off a cliff" after they give birth. In theory supplementing progesterone would help postpartum depression better than allopregnanolone. No one can afford to do that study because there'd be no pay off, as all the important patents have expired.

[0] https://en.wikipedia.org/wiki/Allopregnanolone

[1] https://scholar.google.com/scholar?q=allopregnanolone+fluoxe...

[2] https://en.wikipedia.org/wiki/Gamma-Aminobutyric_acid