Sometimes, but not always. In chemistry, catalysts can help initiate or facilitate chemical reactions, but there is often another input required to kick start the process (e.g. heat). A catalyst won't do anything if there are other things missing.

We know that cannabis can act as a catalyst for schizophrenia, but we also know that not everyone who is predisposed to schizophrenia develops it 100% of the time after cannabis use. There are degrees of predisposition, and a bunch of other factors that contribute to this.