you have already received a perfectly crafted response. I have nothing to add.
Yes, it's true if the antidepressants affect serotonin, which Effexor does. 5-HTP is a metabolite of tryptophan, which in combination with co-factors manufactures serotonin in your body. The theoretical risk is that you can produce too much serotonin effect, something called serotonin syndrome. If you want a natural remedy for sleep, I would start with something called melatonin, the body's natural body clock regulator. 1mg would be a good dose, taken a half hour before bedtime. If that doesn't work, you can try a homeopathic remedy called Calm's Forte. Neither will interfere adversely with what you're taking, though if you resume the trazadone it's so sedating I wouldn't take anything else that helps sleep. A lot of times you have to either do natural or medication, since there are sometimes conflicts. The magnesium is a good idea, however, as antidepressants frequently deplete the body of magnesium.