Why do some people but not others develop substance use problems?

- [Instructor] As it turns out, only a very small number of substance users become substance abusers. And this is something that we really don't know too much about. We don't know why certain people, but not others, move from use to abuse. And we don't really know how use generally progresses to abuse. But even though we don't have a complete model, we do have a number of theories that pertain to this. And that's what I want to go over in this video. The first model I want to talk about is the common syndrome theory, which is also sometimes called the problem behavior theory. And this theory revolves around the idea that maybe there is one, single underlying factor, a drug use propensity, that might put people at a higher risk for abusing substances. But this is really deterministic. It kind of implies that anyone who has a drug use propensity will develop substance abuse problems, and that seems pretty severe. A more nuanced way of talking about this is to use what researchers sometimes refer to as the Swiss cheese model. So here we have a piece of Swiss cheese, and of course it has holes in it. So imagine that every individual on Earth is a unique slice of Swiss cheese. So the placement of holes on each individual slice and the size of these holes and the number of holes vary from person to person. And so we can imagine that the solid parts of the cheese represent things that can protect us from substance abuse. And so the more solid area you have, the less likely you are to use substances. The holes, on the other hand, represent risks. So individuals with many holes, or with really large holes, would be at a greater risk for substance abuse. So maybe we can imagine someone whose friends use substances, and that opens the door for their use as well. Or maybe they have a relative with a substance abuse problem. And in fact, there are many different types of risk factors for substance abuse. And we can think about these different risk factors as being individual slices. So let's say that we have three slices of Swiss cheese here. And each represents a different kind of risk factor. So we have biological risk factors, things like genetics. Psychological risk factors, so maybe certain personality factors that are correlated with addiction. And we also have social risk factors. Things like having friends who use substances, which we talked about earlier. And of course, these slices are different for each individual person. They might have more holes in one and fewer in another. But everyone has some unique combination of risk factors. So now let's try to use this as a way to talk about why some individuals develop substance abuse problems and others don't. And to do that, I want you to imagine that you're shining a laser pointer through these different slices of cheese. So I have three laser pointers here, and these laser pointers represent substance use for different individuals. And if the light hits a piece of the cheese, it'll stop. But if the light goes through a hole, it will continue to move forward. And it is only when the light reaches the back wall, only when it has passed through all of the holes and in the right combination, will someone develop addiction. So let's say we have someone who uses substances, but they don't have a lot of risk factors. They don't have a lot of holes in their Swiss cheese. In that case, the cheese will block the laser pointer beam. And the person will not develop addiction. But let's say that we have someone else who does have some risk factors. Maybe they have a relative who has a substance abuse problem. In that case, some of the light will get through. But if they have fewer holes in their other Swiss cheese slices, or if they aren't lined up in the correct pattern, then the light will stop there. But imagine we have someone else, and maybe they have a lot of holes in their Swiss cheese, they have a lot of risk factors. Or maybe they have an average amount, but they're lined up in a very particular way. In this case, the laser will be able to shine directly through the holes of the Swiss cheese for all of the slices, and will illuminate the back wall, meaning that that person will develop addiction. And hopefully I didn't confuse you too much with this laser pointer Swiss cheese model, but the takeaway's that each individual person has a unique combination of risk factors or things that will make them more likely to abuse substances. And while a lot of individuals might use substances, substance abuse problems will only develop when these risk factors line up. So when they're combined with each other at the right time.