Persuasions, the online Jane Austen Journal, offers many articles about Mansfield Park. Click here to find them. Of particular interest is Crawfords on the couch: a psychoanalytical exploration of the effects of the "bad school" on Henry and Mary Crawford, January, 2006. Here's the description of why Mr. C and Miss C were referred to the doctor:
Miss C was referred to my practice by her half-sister because of symptoms of depression, described as "low spirits," "refusing dinner invitations," and "playing plaintive airs upon the harp." Mr. C was referred to my practice by Dr. G, also because of symptoms suggestive of depression, described as "reading Shakespeare by the hour," "leaving half his dinner untouched," and "refusing even my best claret." These symptoms, according to the Gs, increased "most alarmingly" with an announcement in the London papers last fall of a marriage between Miss Frances Price and Mr. Edmund Bertram, with whom Mr. and Miss C respectively were, according to the Gs, deeply in love.