I've been taking melatonin most nights for about ten years. I haven't noticed any negative effects, other than I'm not sure if it really helps me anymore. I sta

I've been taking melatonin most nights for about ten years. I haven't noticed any negative effects, other than I'm not sure if it really helps me anymore. I started early in college when I realized my high school sleep schedule (less than 5 hours on week nights) wasn't going to work with more demanding academics. It quickly "solved" my sleep issues, but I've continued to take it most nights. My sleep schedule now is pretty regular and great, and I forget to take melatonin every so often and never really notice a difference. So it could be that I have tolerance, but it just doesn't matter since my routine is effective at maintaining good sleep. I agree with exercise helping immensely, but I don't drink any caffeine so I can't comment on that.