Neurotransmitter control via biofeedback?
Firstly, you wouldn't be directly controlling neurotransmitter.  From the human perspective, you'd be controlling higher-level events (and they aren't necessarily describable on more than a phenomenological level).  Of course, this would also lead to some changes in neurotransmitter release, but in a complex way: that's all handled at a lower level by the cells.

That being said, neurofeedback is a (the?) clinical practice that most closely matches your question.  If you look at the references in the wiki page I linked, you will see lots of papers reporting on the findings and techniques.  I do not know the current state of the research.