To draw a conclusion as to the validity/soundness of a proposition/argument based upon the mental state of the person making it would be to commit a non sequitur.
Why? Because even a severely mentally ill person might, despite their illness, be more than capable of constructing perfectly cogent claims. A person's mental state is not a reliable predictor of the quality of the claims a person makes. A condition with paranoid and/or delusional traits might lead a person to more frequently make claims that fail to bear up to scrutiny, but the condition alone is a woefully insufficient indicator as to the truth value of individual claims made by a person suffering from such an illness. It would constitute a similar error to conclude that a person of entirely 'healthy mind' (if such a thing exists), will adhere to some imaginary flawless philosophy or will provide only unassailable arguments and irrefutable claims.
A claim is typically best evaluated against evidence and logic. This protects against a whole raft of logical fallacies, such as ad hominem, appeal to authority and appeal to faith (to name but a few).