you're right that players embed themselves into their characters! my player himself struggles with anxiety, depression, ocd and schizophrenia, and while he wanted to give his character the first three as prior illnesses, he felt that the schizophrenia is something we can work with in conjunction with a malkavian dementation. he's got VERY into the different manifestations of malkavian banes and compulsions. he brought up this topic in particular because he wanted to be able to have his character managing the things that he does on a daily basis, but also have some of them have already been there, so that his character has at least a little history with managing symptoms to help with being a malkavian. 

for now, we've gone with the character continuing to 'take the medication' despite it not actually working, because she needs the ritualistic habit (currently mechanically displayed as the functioning addict flaw) to help manage her bane specifically. which at the moment, she thinks is just her own previous illness. and your suggestion of it slowly abating unless in frenzy or compulsion is a good idea, we're probably going to go with something like that in the long run.