There are a few weight neutral drugs, Lamotrigine, abilify, also a new version of zyprexa (Zydis)...
Lamotrigine is an anticonvolsant that is a really good antidepressant and weak mood stabiliser, abilify and zyprexa are both antipsychotics that are good moodstabilsers
I have put on 20 kg since my diagnosis, then lost 15 then put it back on then lost 5 and put in on.... so I understand the yo yo!!!!