Talking to the Dead
The hero of this story is a therapist, so it's not really a shocker that "talking" is a major motif. But what does end up kind of being a surprise is that all of Cole's struggles with the dead—and all of their efforts to terrorize him—really come down to a desire to communicate and be heard.
Sure, there's a certain amount of magical hocus-pocus involved in the fact that Cole can hear and see them, but his powers only reach their full potential (and stop damaging his life and relationships) when he allows them to tell him their troubles.
The result is miraculous: he can finally confide in his mother, his school life improves, and he manages to help a whole bunch of (dead) people with their unfinished (earthly) business.
And that includes Malcolm, too, who through his chats with Cole finally realizes that he's dead. It's the supernatural version of the psychological breakthrough, and it sets Malcolm free.
So, really, the movie is about the benefits of therapy. Freud would be so pleased. In fact, he told Shmoop that just the other day.
Hey, could someone turn up the heat in here?