It would be silly to prescribe antipsychotics if all they did was cause psychosis. When properly administered under a doctor's care and a pharmacist's oversight, most patients should be fine. There will be people with bad reactions, sure, especially with the variety of things anti-psychotics can be used for--not just schizophrenia but bipolar disorder, for example. And there's always the cases where the anti-psychotics are not causing the psychotic episode, but rather failing to properly treat it.
Anti psychotics can cause psychosis. Psychosis is caused by chemical imbalances in the brain, while the idea of an anti psychotics is a great one, by assisting those chemical imbalances in righting themselves by supplementing with what the body isn't producing, the reality is, if you end up with too much of that chemical, you could end up inducing psychosis, or making it worse, especially if someone is taking these drugs that isn't psychotic in the first place.
No, anti-psychotics do not cause psychosis, they control potential psychoses in certain individuals, and if prescribed under the care of a responsible doctor,can do a great deal of good for someone who has psychotic tendencies. These medications are formulated to compensate areas of the brain that need to be regulated, and therefore are ideally helpful.
It's certainly possible for anti-psychotics to appear to cause psychosis, or even trigger psychotic episodes, particularly when not taken under a doctor and pharmacist's care, and also the wide range of disorders the drug class can be used for--not just schizophrenia, but bipolar disorder. However, it's likely that the drug is simply failing to properly medicate psychotic episodes that would've occurred without the medication.