When Hannibal talks to Clarice for the first time, he tells her a chilling story: "A census taker once tried to test me. I ate his liver with some fava beans and a nice Chianti." While this story is already unsettling enough as it is, the hidden meaning behind his words makes it even worse. Hannibal was actually making a subtle joke that he wasn't taking his medication.
Although it isn't explicitly stated, we can assume that Hannibal has some sort of mental illness, whether that's depression, post-traumatic stress disorder, or antisocial personality disorder. The look in his eyes, along with his blatant lack of remorse for others, makes that clear as day. Monoamine oxidase inhibitors (MAOIs) are used to treat depression and a variety of other mental health problems. While taking MAOIs, it's extremely dangerous to eat certain foods, including liver, fava beans, and wine. That means Hannibal wouldn't have been able to eat the grisly meal he described if he had been taking his medication. Leave it to Hannibal to make such a dark, complex joke.
If you or someone you know needs help with mental health, please contact the Crisis Text Line by texting HOME to 741741, call the National Alliance on Mental Illness helpline at 1-800-950-NAMI (6264), or visit the National Institute of Mental Health website.