I have a study quoted that says the same exact thing.
IMO, if you can get the same chemical (L-Tryptophan is converted to 5-HTP in the brain anyway, but it keeps the other metabolites of the drug out of where they shouldn't be) in a much safer, natural way... why bother with pills?
I read the study you linked. It does not say that it put the liver under stress. That's just your understanding of it. Elsewhere in the study the usefulness of 5-HTP is detailed:-
"Improves Well-Being in Depressed Persons
Serotonin in the central nervous system is recognized as a causative
factor in some depressed persons.6,7 A comprehensive review of seven
open and seven controlled clinical studies found that oral consumption
of 5-HTP improved mental and emotional status in 60 to 70 percent of
depressed people. "
"Improves Sleep Quality
Studies have shown that 5-HTP influences the quality of sleep by
increasing REM (rapid eye movement) sleep. Administration of 5-HTP in
the evening prior to bedtime has been shown to increase the duration of
REM sleep and decrease the amount of non-REM sleep"
"5-HTP–A Free-radical Scavenger
The OH group which is added to tryptophan in the formation of 5-HTP
gives 5-HTP antioxidant properties.18 (Compounds such as vitamin E and
flavonoids derive their free-radical quenching ability from OH groups,
which donate electrons to oxidants.)
5-HTP quenches a variety of free-radicals. This is in contrast to
tryptophan, which is " sensitive " to oxidation."
^^^^I would only presume that all 3 of these reported affects of 5-HTP would help with a comedown. Certainly I can personally vouch for improved mood and sleep.
Have you tried 5-HTP Folley or just base your advice on what you have read?