Many years ago a Japanese company supposedly had some contaminant in their process. This was never proven however, and many think the whole thing was put up by Eli Lilly who had just released Prozac. If you search the net you'll see.

The spike in the gas chromatography studies was called substance X. (or something like that).

Tryptophan has returned. I use the NOW brand. I find 500mg plenty for me, and it has some good anti-anxiety effects for me when I need it.

SSRIs (Cymbalta is part SSRI)...keep the serotonin the synaptic cleft and it doesn't get recycled. So the cell stops making it. I think the withdrawal is the low levels of serotonin present, and taking the tryptophan precursor helps restore normal functions.

Low serotonin often means low melatonin. So if you have sleep problems, consider taking methylB12 too...it is the specific cofactor in making melatonin from serotonin.

Usually the other neurotransmitter norepi, is is better supply.
The precursor for it is tyrosine but I think most people don't need support for that. Tryptophan doesn't get thru the BBB as easily as other amino acids. So take the tryptophan away from a major protein meal, and perhaps give it a boost with a bit of candy/etc. This helps tryptophan get thru faster.

Using 5-htp is also an option, and less is needed (usually only 50 or 100mg at bedtime). I don't do well with 5-htp and get irritable from it. The tryptophan is much gentler IMO.