I have encountered some mental-health professionals who, despite their training and official professional doctrine, definitely do apply the categories of good and evil. I shall leave aside the debate about homosexuality, which in the present state of things is more about competing ideologies than scientific fact. But depressed people, narcissists, and multiple-personality sufferers, among others, are sometimes held morally accountable for their condition. Sometimes such people are held accountable for letting themselves get into such a state; other times, they are held accountable for continuing to be in such a state. When it's both, we have full-blown moral judgment. Even granted Jesus Christ's wise injunction "not to judge"—i.e., not to claim knowledge that only God can have—such a judgment is doubtless objectively true in some cases; in others, it doubtless is not. But the mere fact that it naturally suggests itself puts the lie to the widespread claim that the conditions for which people are sometimes judged are just mental illnesses. Such "illnesses"—sometimes in their origin, sometimes in their persistence—can themselves be symptoms of evil choices made in the heart, ones that could have been otherwise.
I do not suggest that we deal with such persons merely as "sinners" rather than as "patients." We know too much about brain chemistry and other influences to dispense with treatment in the familiar sense. But it seems reasonable that, if people must want to get well in order to get well, then obversely, something evil that they want accounts for their getting or staying sick.
M. Scott Peck, of The Road Less Traveled fame, has had some interesting thoughts on this. He does not pretend to have an all-encompassing theory, and of course neither do I. But one thing I'm sure of: Satan, who is real and personal, is especially active among the mentally ill.