While I cannot say that “Aspartame” caused “narcolepsy-like” symptoms, I can say it has a “bad-effect” on me. When drinking a lot of sodas “sweetened” by it — I had effects that made me dub it “stupid drug”.
Similar effects to “Excessive Daytime Sleepiness”. At the time, I was not diagnosed as narcoleptic. I cut out Aspartame from my diet years ago because I didn’t like its effect on me. Could its effect have worsened the narcolepsy and I didn’t know it? I am not sure. Now, I am diagnosed as narcoleptic and I watch my diet closely — and don’t drink or eat anything “sweetened” with Aspartame.
Yes, I think it causes “bad effects” in narcoleptics. No, I don’t think we are going to see a “scientific study” to prove anything — it’s just not economically feasible today. My personal recommendation is to stay away from the stuff. But that is without any scientific or medical justification.