If it's there, there'a a likelyhood that using stimulants will unmask it. Stimulants do cause symptoms characteristic of paranoid schizophrenia; if it's latent in you, anything can act as a trigger (traumatic incident, drugs etc).
Basically, if there's a history in your family (of schizophrenia)and you decide to take stimulants, you might not be the same person after using them. That also applies to psychedelics, dissociatives & cannabinoids. You have to do the risk/benefit asssessment for yourself...
Can using these classes of drugs trigger schizophrenia? Yes, but only latent illnesses result in long term psychosis. Most people recover once the drug is removed from their system
Is it likely I'll be one of those people who lose the plot after using them? Look at your family history. If you have schizophrenic relatives, your chances might be higher than average, but no-one can be certain. Latent psychiatric illnesses triggered by drugs is a known cause, but latent = hidden, so you can only make a guesstimate.
Some drugs do cause neurotoxicity eg meth, PCP (some such as MDMA only seem to cause it with raised body temp or other specific criteria).
Overall, you have to ask yourself if you think you're one of the 'at risk' people. If so, do you think it's worth it?
Thing is, that's how a lot of life operates, you make a decision, act on it and there are consequences. Sometimes they are irreversible, so you should find out as much as you think you need before making such a descision (I'd love to be able to grow another left hand - like a salamander - but I know I can't, so I have to live with it).
[/ketamine rant!]
PS If you're doing coke, it's not your brain you need to worry about, it's your heart