How Does Prozac Work? Jonah Lehrer

What’s the point of neuroscience? Why do we spend billions of dollars investigating those three pounds of flesh inside the head? Sure, human nature is interesting, and self-knowledge is a virtuous pursuit, but let’s be honest: we study the brain because we don’t want to die. Because we want cures for awful afflictions. Because we’re desperate to avoid depression and addiction and dementia. The only way to justify the terrific expense of biomedical research is medicine.

Here’s the bad news: I think neuroscience has yet to deliver on its therapeutical potential. We’ve learned an astonishing amount about the brain in recent years – a ten year old textbook is totally obsolete – but all this shiny new knowledge has yet to heal us. As a result, we’re still stuck with pills and treatments that are frustratingly ineffective.

Consider depression. Every year, approximately 7 percent of us will be afflicted to some degree by the awful mental state that William Styron described as a “gray drizzle of horror . . . a storm of murk.” This is a big societal problem, which is why 24.4 million prescriptions were filled for fluoxetine (the generic version of Prozac) in 2010 in America.

The first thing to say about fluoxetine is that it’s an old drug, having been introduced in the early 1970s. (Like many medical treatments, it was discovered largely by accident, when researchers realized that a common anti-histamine had anti-depressant properties.) Until recently, scientists assumed they knew how fluoxetine/Prozac worked. The story was simple: depression results from a neurotransmitter imbalance in the brain, in which patients suffer from a shortage of chemical happiness. The little blue pills cheer us up because they give the brain what it has been missing – a dose of serotonin.

There’s only one problem with this theory of anti-depressants: it’s almost certainly wrong, or at the very least woefully incomplete. Experiments have since shown that lowering people’s serotonin levels does not make them depressed, nor does it worsen their symptoms if they are already depressed. And then there’s the “Prozac lag”: although anti-depressants increase the amount of serotonin in the brain within hours, their beneficial effects are not usually felt for weeks.

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