In the beginning of Twilight, Edward is suffering from severe depression, but he doesn’t know it. He has reached the point at which everything has gone numb, music is an anesthetic, and unhappiness is the new normal. He has reached the human age of dying, and he would almost welcome death. But he can’t.
Edward is lonely. And still doesn’t know it. Enter Bella Swan, the girl with delicious blood and the chocolate eyes. In many ways, Bella becomes his new addiction, replacing blood, the one he can’t have. People may complain that Bella is unhealthily codependent on Edward, but it is worth noting that Bella interacts with other people besides Edward in Twilight and thinks about other things besides him. Midnight Sun is 100% Bella 100% of the time.
I do understand it. You do nothing, each day–or feel like you do–but you get used to it. You don’t matter, you hate yourself, living inside your head is torture, but you’ve been living so long like this that you think nothing is wrong, at least until you meet a person who isn’t just an anesthetic or a distraction–this person makes you happy. This person solves everything.
While Bella doesn’t have problems with wanting to eat everyone in sight, she seems to lack connection with anyone besides her mother, and even that relationship fades throughout the series (possibly because she found a new vampire mommy?). As for Charlie, he and Bella don’t seem to have laid the framework for an emotionally open relationship (and yes, I know girls don’t tell their fathers everything, but even I, stoic extraordinaire, have a better relationship with my dad than Bella does with hers). Perhaps sensing this lack in her life, Edward wastes no time installing himself as her confidante, and much as Bella might protest at first, she comes to rely on him for the only emotional depth in her life (healthy). Just as Edward is Bella’s escape from the dreariness and insincerity of humanity, Bella is his escape from vampirism. Bella is the perfect opportunity to play at being human. He doesn’t just take Bella to prom so that she’ll have the full range of human experiences–there is a hidden, ulterior motive. He wants to go to prom because it will only happen once in Bella’s life, and thus have meaning to him. Through her eyes, he experiences humanity in all its ephemeral delights for the first time in eighty-odd years. To use less big words, Edward will go to prom with a pretty girl and it will mean something because it will never happen again.
While Edward genuinely believes that vampirism is a horrible fate that he can’t condemn her to, she is also his strongest link to the living. If Bella lives, he will continue to vicariously grow up with her as she goes to college, gets a career, and faces ordinary challenges. When she dies, he will find a way to kill himself and follow her. In this way, he will approximate a human existence. And then he will be rid of blood forever.
I often hear that Twilight’s version of vampirism is a metaphor for sex, but I always read Twilight as an allegory for addiction. Insatiable craving follows Edward wherever he goes, but he drowns it out with fast cars and music and Bella Swan, mostly Bella. In fact, as the series progresses, he tells her that her blood no longer tempts him because his entire being shies away from hurting her. Her preservation is linked to his. In Twilight, people don’t recover from addictions–they just replace them with socially acceptable ones. And Bella is his addiction of choice.