So the first antidepressants were made from, of all things, rocket fuel, left over after World War II. Which is fitting, seeing as today,one in five soldiers develop depression, or post-traumatic stress disorder or both. But it's not just soldiers that are at high risk for these diseases. It's firefighters, ER doctors, cancer patients, aid workers, refugees -- anyone exposed to trauma or major life stress. And yet, despite how commonplace these disorders are, our current treatments, if they work at all, only suppress symptoms.
In 1798, when Edward Jenner discovered the first vaccine -- it happened to be for smallpox -- he didn't just discover a prophylactic for a disease, but a whole new way of thinking: that medicine could prevent disease. However, for over 200 years, this prevention was not believed to extend to psychiatric diseases. Until 2014, when my colleague and I accidentally discovered the first drugs that might prevent depression and PTSD. We discovered the drugs in mice, and we're currently studying whether they work in humans. And these preventative psychopharmaceuticals are not antidepressants. They are a whole new class of drug. And they work by increasing stress resilience, so let's call them resilience enhancers.
So think back to a stressful time that you've since recovered from. Maybe a breakup or an exam, you missed a flight. Stress resilience is the active biological process that allows us to bounce back after stress. Similar to if you have a cold and your immune system fights it off. And insufficient resilience in the face of a significant enough stressor, can result in a psychiatric disorder, such as depression. In fact, most cases of major depressive disorder are initially triggered by stress. And from what we've seen so far in mice, resilience enhancers can protect against purely biological stressors, like stress hormones, and social and psychological stressors, like bullying and isolation.
So here is an example where we gave mice three weeks of high levels of stress hormones. So, in other words, a biological stressor without a psychological component. And this causes depressive behavior. And if we give three weeks of antidepressant treatment beforehand, it has no beneficial effects. But a single dose of a resilience enhancer given a week before completely prevents the depressive behavior. Even after three weeks of stress. This is the first time a drug has ever been shown to prevent the negative effects of stress.
Depression and PTSD are chronic, often lifelong, clinical diseases. They also increase the risk of substance abuse, homelessness, heart disease, Alzheimer's, suicide. The global cost of depression alone is over three trillion dollars per year. But now, imagine a scenario where we know someone is predictively at high risk for exposure to extreme stress. Say, a red cross volunteer going into an earthquake zone. In addition to the typhoid vaccine, we could give her a pill or an injection of a resilience enhancer before she leaves. So when she is held at gunpoint by looters or worse, she would at least be protected against developing depression or PTSD after the fact. It won't prevent her from experiencing the stress, but it will allow her to recover from it. And that's what's revolutionary here. By increasing resiliency, we can dramatically reduce her susceptibility to depression and PTSD, possibly saving her from losing her job, her home, her family or even her life.
After Jenner discovered the smallpox vaccine, a lot of other vaccines rapidly followed. But it was over 150 years before a tuberculosis vaccine was widely available. Why? In part because society believed that tuberculosis made people more sensitive and creative and empathetic. And that it was caused by constitution and not biology. And similar things are still said today about depression. And just as Jenner's discovery opened the door for all of the vaccines that followed after, the drugs we've discovered open the possibility of a whole new field: preventative psychopharmacology. But whether that's 15 years away, or 150 years away, depends not just on the science, but on what we as a society choose to do with it.
Thank you.
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