Hi there!
GABA as body neurotransmitter increases serotonin, like the similar neurotransmitters 5-HTP and L-tryptophan. Those are s'posed to help sleep, but I didn't tolerate them.
When I started GABA it seemed a last resort as no supps had helped up to then, and it being such an unusual one I was surprised in how many areas it helped. Mainly deep muscle relaxation and thus pain (most strikingly bladder pain). For sleep it was the first thing that helped at all without harming, some periods since then I've only been up 4x per night, but often still 6-10x. So it was never good enough for sleep on its own and I've always looked for more help.
Some used to say the molecules are too big to cross the blood-brain-barrier (BBB), which would mean it can't help sleep, but this is standing corrected in recent studies. My sleep lab psychiatrist confirmed the effect it's having on me means it is crossing my BBB.
To put that into context, in case anyone's interested...
My other main sleep supps:
None of the magnesiums up to then helped, and passiflora didn't until I doubled the max. dose, so that's become my other mainstay. This remained fairly OK for a long time until improvement from adding Huberman's ideas of apigenin, myo-isonitol and magnesium threonate, plus looking towards the sun (or now in November a daylight lamp), always getting up at the same time. This made it possible to often get 7-8h of deep sleep per night, but 1-2h of sleep breaks plus 1-2 dozing until I had enough to keep my Ache down in the daytime.
I take loads of other supps too for my various reasons, and these are the ones that are supposed to help sleep: v.B12 as methylcobalamin, magnesium malate, PQQ, CoQ10, quercetin, luteolin & honokiol, rhodiola. (v. B6 as P5P not at the moment cos it got too high.) I take most in the evenings, but it doesn't make a difference to sleep if I don't take them.
2nd gen. antihistamine
Now the 3rd jab, the MCAS flare triggered by it and the 2nd gen. H1-antihistamine I'm adding for that in the evenings are for the first time since I had fibro giving me brilliant, almost normal sleep: 7-8.5h of concentrated deep sleep, with 3-4 5' breaks - what luxury! One reason is that the antihistamine is fluid retaining which means even slightly dryer mouth/lips, but also a "dry" bladder - very useful at night, when I take it, hardly any urge any more. As it's 2nd generation it doesn't zombify me in the daytime (like tryptophan, 5-HTP, CBD, melatonin and amitriptyline did). My GP feared I'd be zombified by an antihistamine, but my allergist recommended that one and it's worked for me for a month. It didn't work long for sleep after the 2nd jab....
(This is all having got and keeping all local pains down to essentially zero by trigger prevention, exercises, stretches, massager, supps etc. and the overall ache by pacing well, esp. in the last 5-6h before sleep: no socializing, no TV, no blue light, subdued etc. and a cold shower to get any stress or ache or unrest down).