Your Brain on Drugs... Literally

We have all seen or heard about this ad before, a few too many times for it to be easily forgotten. Still, its ridiculousness has probably driven more teenagers to drugs than away from them. But when it comes down to science, the anti-drug campaign is a little more accurate than it may seem.

1987 "Your Brain on Drugs" PDFA Ad Campaign Poster

Before you pretend that this issue is entirely foreign to you, we're all adults here, and if it was only that one time...

But seriously, most people know somebody with an addiction, whether they are aware of it or not. If you think you don't, think again, cause your girl didn't come to AP Bio class all year to attend a substance abuse program. Addiction isn't always what you see on Intervention, this information applies equally to caffeine and nicotine (and in some cases food, video games, and gambling) as it does illicit substances. I know you're thinking, "Sofia, this isn't health class, stop telling me that drugs will mess with my brain." But trust me, I'm the last person to tell you what to do. That being said, some facts can't be ignored, so here are a few that I found interesting.
There's a reason that drug and alcohol addiction/dependence are now categorized as chronic brain disorders (as well as mental illnesses). The human brain is an intricate and complicated organ, and its inner workings are not yet fully understood by the academic world. As with any disease, a lot of factors can influence an individual's risk of becoming addicted to some substance. Our whole lives we hear about, are exposed to, and are given access to addictive substances, so why aren't we all addicts? Certain factors (genetic and environmental) can lower an individual's threshold, making them more vulnerable when the opportunity arises. Nurture definitely plays a huge role, but about 40 to 60 percent of risk is based on genes and epigenetics. This means that addiction is fairly heritable, which is why we often see things like alcoholism in multiple individuals in the same family.

Heritability of Addictive Disorders (h squared range represents the amount of variance caused by genes)

Although how exactly addiction is inherited isn't known yet, it is far from Mendelian. Biological and behavioral similarities (called intermediate phenotypes or endophenotypes) shared by addicts give some indication of what genes may be involved. For example, substance abuse is often prevalent in people with anxiety disorders, and geneticists speculate that this has something to do with a mutation in a gene that regulates serotonin levels. But this is just one of many possible factors that contribute to an individual's possibility of developing a dependency. Understanding the genetics behind addiction on a deeper level has the capability to help thousands of people, like this gene therapy treatment that, if it reaches the market, promises to eliminate the high gotten from cocaine.


Whether you experiment with drugs in adolescence can be blamed more on your peers and your environment, but as you reach adulthood your continued use and chances of becoming dependent become increasingly based on genes. This doesn't mean that teenagers are immune to addiction, though, when in fact it takes fewer uses of a substance for us to get hooked than it would an adult. Because the prefrontal cortexes of young brains are still developing, we make a lot of poor decisions while simultaneously forming the connection that those decisions can't be that bad if they make us feel good. As I'll talk about a bit more later, the release of dopamine (the feel good brain chemical) is meant to reward the body for positive/productive behaviors, such as exercise or eating high calorie foods, and motivate you to make them a habit. The immense amount of dopamine that comes with drug use makes the normal reward system look pathetic, and our malleable brains quickly soak up the idea that this drug is in some way beneficial, more so than exercise or chocolate or sleep or music.

Your brain on dopamine pretty much

Your brain on drugs pretty much

Still, that first time is critical. Each time you use a drug, it rewires your brain in various ways, many of which lower your chances of avoiding addiction or dependency. There are a couple different ways that addictive substances can affect your brain, but it all comes down to messing with the cell signaling in certain critical regions. This includes the extended amygdala (stress, irritability, and withdrawal), the basal ganglia (reward, pleasure, and motivation), the hippocampus (learning and memory), the cerebellum (motor movements) and the prefrontal cortex (problem solving and self control). I know, I just named, like, the entire brain.

Labelled Sections of the Brain (not all of them, but some important ones here)

There are a couple different ways that addictive substances can affect signaling pathways in the brain. Drugs like marijuana and heroin mimic naturally occurring ligands called neurotransmitters that are released from neurons (nervous system cells). These chemicals bind to receptors in different parts of the brain and trigger various responses. For example, the brain lipid anandamide is synthesized inside of neurons as needed to maintain homeostasis. When it's released from a cell it binds to cannabinoid receptors (remember G-protein coupled receptors?) before quickly being broken down. An anandamide signal can trigger pathways that stimulate appetite, regulate mood, release dopamine, or induce neurogenesis (the production of new brain cells). This neurotransmitter is released, after rigorous exercise for instance, producing a natural kind of high and rewarding you with small, controlled amounts of dopamine. Tetrahydrocannabinol (THC) in marijuana is structurally similar to anandamide so it is able to bind to the same cannabinoid receptors and trigger similar pathways.

Anandamide Structure Compared to THC

But, as we very well know, similar is not the same as identical, and any difference in structure leads to a difference in function. THC stays intact in your body for much longer than anandamide and enters your system in much greater amounts, temporarily overwhelming the regulation of these pathways. This results in a real high, characterized by the excessive release of dopamine, along with other complicated phenomena. Heroin, considered the most addictive drug, causes your brain to release up to 3 times as much dopamine as a typical release from, say, a jog. This is all well and good (actually its not, but its not all bad), until it goes on for a bit and your brain closes off dopamine receptors to combat the frequent and excessive release of the chemical. That's when you stop feeling as good as you used to about that stuff you love before- exercise, chocolate, sleep, music- unless, of course, you're high.

While many people successfully recover from addictions, your brain can only recover up to a point. It depends on the type of drug, how long you used it, and the amount you used, but in any case a lot of brain cells were sacrificed (even though contrary to popular belief you can grow a small amount of new ones).

Control brain (left) vs. the brain of a methamphetamine addict (right)

Activity in a healthy brain vs. the brain of a cocaine addict in various stages of recovery

It's crazy to think about a person's potential diminishing with each use of a drug. Whether you blame the drug epidemic in this country on lousy childhoods, lousy genes, big pharma or society, "your brain on drugs" didn't really work at spreading awareness about addiction. But preaching abstinence never works as much as education. I hope you found this as interesting as I did, and that you hesitate before the next time you put your brain in a frying pan.