Read up the studies. I'd say it's probably best studied in schizophrenia, they have all kinds of cognitive improvements on antipsychotics, rather very unpleasant drugs.

Dopaminergics like amphetamines, ritalin or bromantane do help with anxiety, it's common knowledge, but I don't think the effect is sustainable long term, at least not that I've heard. More common for that effect to fade away with time on chronic dosages and more of a jitterness surface later on.