On the metacognitive deficit:
“Evils of the soul escape most people; for this reason they are worse—they prevent those who suffer from sensing them”
τὰ δ᾿ ἐν ψυχῇ λανθάνει τοὺς πολλοὺς κακά, διὰ τοῦτ᾿ ἐστι καίω, προσαφαιρούμενα τὴν αὑτῶν τοῦ πάσχοντος αἴσθησιν
This and the following passage are from Plutarch’s On Whether Sickness of the Body or Mind Are Worse (Moralia 500 ff). The following (especially the last line of the first paragraph) appears to perpetuate the stigmatizing of mental illness. And it does: many behaviors we today would see as parafunctional and requiring therapy, ancient authors viewed as issues of will.
“Just as, therefore, the storm which keeps you from docking is more dangerous than the one that won’t let you sail, the storms of the soul are worse when they do not allow a person to control or put down his troubled thoughts—this person goes without a helmsman, without ballast in confusion and wandering, taking off in steep and opposite courses until suffering a harrowing shipwreck and crushing his life. This is why it is worse to suffer sickness of mind than the body: For those who are sick, merely suffer; the sick of mind suffer and harm others.
But why is it necessary to repeat the great number of afflictions? Current events remind me of them. Do you see this immense, mix up crowd which clings together and mixes around the seat of government and the market?”
Ὥσπερ οὖν ἐπισφαλέστερος χειμὼν τοῦ πλεῖν οὐκ ἐῶντος ὁ κωλύων καθορμίσασθαι, οὕτως οἱ κατὰ ψυχὴν χειμῶνες βαρύτεροι στείλασθαι τὸν ἄνθρωπον οὐκ ἐῶντες οὐδ᾿ ἐπιστῆσαι τεταραγμένον τὸν λογισμόν· ἀλλ᾿ ἀκυβέρνητος καὶ ἀνερμάτιστος ἐν ταραχῇ καὶ πλάνῃ δρόμοις λεχρίοις καὶ παραφόροις διατραχηλιζόμενος εἴς τι ναυάγιον φοβερὸν ἐξέπεσε καὶ συνέτριψε τὸν ἑαυτοῦ βίον. ὥστε καὶ ταύτῃ χεῖρον νοσεῖν ταῖς ψυχαῖς ἢ τοῖς σώμασιν· τοῖς μὲν γὰρ πάσχειν μόνον τοῖς δὲ καὶ πάσχειν καὶ ποιεῖν κακῶς συμβέβηκε.
Καὶ τί δεῖ τὰ πολλὰ λέγειν τῶν παθῶν; αὐτὸς ὁ καιρὸς ὑπόμνησίς ἐστιν. ὁρᾶτε τὸν πολὺν καὶ παμμιγῆ τοῦτον τὸν ἐνταῦθα συνηραγμένον καὶ κυκώμενον ὄχλον περὶ τὸ βῆμα καὶ τὴν ἀγοράν;

Your comments about stigmatizing mental illness seem a bit oversimplified. For one thing, many mental illnesses are ‘issues of will’ if what that means is that they lead us to make poor judgments and irrational decisions. If instead what it is to be an ‘issue of will’ is to be fully under a person’s volitional control, then most of the ancient authors who discuss these matters most fully do not think they are unproblematically ‘issues of will’; they see them as deeply engrained patterns of desire, emotion, and thought that we cannot rid ourselves of with a simple act of will, but that we can alleviate if at all only through difficult, long-term practice. Nor do the best ancient psychologists typically suppose that we acquire these dispositions solely through our own free, responsible decisions; they’re well aware that many of them owe their existence to upbringing and culture. It’s true that ancient psychologists underestimate the extent to which psychological problems can be due to purely physiological factors, but they do not suppose that no such problems are due to physiological factors. Arguably they tend to overestimate our ability to change ourselves or improve our condition without medical intervention, but it’s simply false to claim that they didn’t see these things as requiring therapy; many of them think of philosophy itself as a kind of therapy, and their techniques anticipate today’s cognitive psychotherapy in many respects. These matters are fairly well understood by scholars of ancient philosophy, but there are good, accessible discussions as well. Jules Evans’ Philosophy for Life and Other Dangerous Situations is a good popular introduction to the enduring value of ancient Greek and Roman philosophical thought for approaching mental health; though it’s not a scholarly book, it should leave no readers in doubt that the statement above about stigmatizing mental illness is a severe oversimplification at best.
If worrying about stigma leads us to deny that mental illness frequently leads people to cause suffering to others as well as to themselves, then we should stop worrying about stigma. But one would hope that worrying about stigma wouldn’t lead us to be embarrassed to say what is true. Those of us who suffer from some form of mental illness should not be ashamed to acknowledge that it has sometimes led us to bring suffering to others; if yours hasn’t, be grateful for that.
All very fair. Thank you for this.