Alcohol helps with anxiety, but worses dysfluencies. I don't think weed has any effect, but in general I am anxious someone would notice I am high, and am often too tired to talk at all. MDMA made me anxious about my health, so I stopped at pretty low dose, didn't notice any effects in this area. From the legal and accepted drugs, caffeine has no effect, nicotine might have some effect on anxiety unless you have built up tolerance.