Bad Medicine

Oh," said the clerk, glancing distrustfully at Caswell's bloodshot eyes. "You seem a little nervous. Perhaps the portable Bendix Anxiety Reducer—"
"Anxiety's not my ticket, either. What have you got for homicidal mania?"
The clerk pursed his lips. "Schizophrenic or manic-depressive origins?"
"I don't know," Caswell admitted, somewhat taken aback.
"It really doesn't matter," the clerk told him. "Just a private theory of my own