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  • Part of what makes our brains so deliciously amazing, is that they've evolved to reward us and encourage us

  • when we do stuff that helps us survive and spread our genes all over the place.

  • I'm talking about eating and sex having and running from danger.

  • Stuff like that.

  • For hundreds of thousands of years, this system served us well. But in a way, our brains have

  • since gotten too smart for their own good.

  • We've figured out how to make ourselves experience this pleasure when we're not even doing any of those things.

  • By inventing drugs.

  • And we've also figured out how we could do those things.

  • Eating, sex having, getting an adrenaline rush.

  • Recreationally.

  • Instead of for our survival. And sometimes the craving for that feeling can take on a life of its own.

  • And so, by doing these things, we have basically invented addiction.

  • Nice move, brains.

  • But this is why addiction isn't limited to drugs; behaviors can be addictive too.

  • The compulsive urge to use cocaine again and again, the compulsive urge to eat candy bars again and again,

  • are both produced from the same brain circuitry.

  • Same goes for addictions to gambling, sex, eating, even...Reddit.

  • Addiction: it's all in our brains. Mo' synapses, mo' problems.

  • [Intro Jingle]

  • The chemistry of addiction takes place mostly in the brain's limbic system, the set of structures at the center

  • of the brain that controls our emotional and behavioral responses to the information we receive.

  • It's often referred to as the brain's "reward center."

  • And it responds to new information from the nervous system by releasing chemical messengers called neurotransmitters

  • that pass signals from one neuron to the next or to another kind of cell it wants to activate.

  • Your brain produces at least 100 different neurotransmitters and we're finding new ones all the time.

  • But the most important neurotransmitters, when it comes to addiction, are the ones that are released

  • when we do something that's key to our survival and success.

  • Once they're done getting the word out, they're usually re-absorbed back into whatever neurons they originated from.

  • There are two major kinds of neurotransmitters and in a healthy brain they're pretty much in balance.

  • There's excitatory neurotransmitters, which get their target cells all fired up with chemical energy

  • and there's inhibitory neurotransmitters which keep their target cells calm and mellow.

  • Serotonin is an inhibitory neurotransmitter that you've probably heard of; it helps regulate your mood, your

  • your appetite and your sleep cycle.

  • But it's the excitatory ones that you really gotta watch out for.

  • Endorphin, for instance, is released when we exercise, are really stressed or in a lot of physical pain,

  • and it helps with coping and painkilling.

  • And, by far, the most important reward chemical is dopamine.

  • It's released whenever our brain believes we should take strong note of our current behavior, to remember it.

  • It's levels rise in response to pleasurable experience like eating or baby-making.

  • But it's also released when, like, a bull moose is charging us.

  • PAY ATTENTION TO THIS MOMENT! DO NOT FORGET IT!

  • So, yes, the exciting sensation you feel when your dopamine levels are up reminds our brains to do things

  • that are important to our survival.

  • But it's also a large part of what drives addiction.

  • Because addictive drugs are really good at not only messing with our levels of dopamine and other neurotransmitters,

  • they also exploit the brain's ability to vividly remember unnatural highs and motivate itself to find more of them in the future.

  • Scientists have recently started to debate whether dopamine actually makes you feel good,

  • or if it just exists to make you want things more.

  • We've always based the assumption that dopamine makes you feel good on the fact that it makes people

  • and, more commonly, rats repeat activities that increase dopamine levels.

  • But while dopamine definitely has a pleasure component, it may be much more important

  • in simply creating desire, whether or not there's a pleasurable outcome, which is why, maybe, so many

  • addictions continue long after any actual pleasure is gone.

  • Another important factor in addiction is that when the brain is met with the intense stimuli that drugs can cause,

  • it has all kinds of defenses that it desperately uses to restore balance.

  • So after using a certain drug over the long-term, your brain will reduce the number of neurotransmitters

  • or receptors available to it to try to moderate it's effects.

  • This leads to what's known as a hypo-functioning reward system, which makes artifical and natural highs harder to come by.

  • So while your brain on drugs is not technically a fried egg, it is a significantly altered egg.

  • This is why we develop tolerance to certain drugs and why addicts often end up with shiny new psychological

  • disorders they didn't have before their addictions.

  • Now, with all this in mind, drugs that cause addiction screw with your brain activity in two major ways:

  • One, they imitate one of your natural neurotransmitters or two, they artificially change the levels of your

  • neurotransmitters, either by overstimulating their release or inhibiting their re-absorption.

  • So, for instance, heroin and other opiates like codeine and morphine are some of the most addictive substances on Earth,

  • because their structure is very similar to endorphin.

  • They bind to nerve cell receptors reserved for endorphin in huge numbers which magnifies endorphin's painkilling

  • effect, creating a feeling of euphoria.

  • Opiates create far more powerful reactions than any natural stimulus.

  • So once the artificial high is experienced, the brain craves to return to that feeling.

  • Nicotine, meanwhile, takes a different attack vector; first, it mimics a neurotransmitter called acetylcholine

  • which triggers the release of large amounts of dopamine.

  • Then it also sets off the release of other chemicals that leverage it's effect, like glutamate, which plays an

  • important role in memory formation.

  • So, in addition to dopamine being all, "Remember this and do it more!", glutamate is also firing memos

  • off to surrounding neurons, creating what some scientists think is a memory loop that reinforces the habit.

  • Finally, a third way for it to act, nicotine also sets off a flood of an inhibitory neurotransmitter called GABA,

  • which ordinarily calms neurons down, but after 20 minutes the GABA receptors are so desensitized

  • that there's nothing left to get in dopamine's way.

  • Then there's alcohol, which upsets that balance of neurotransmitters that allow body and brain to function as one.

  • It binds to a number of different receptors, including those for acetylcholine and serotonin,

  • which explains it's initially pleasing and, later, sedative effects.

  • More alcohol means slower communication between neurons, but here's the thing:

  • as the brain grows used to alcohol over long-term use it tries to compensate by releasing excitatory neurotransmitters

  • to speed up signal transmission.

  • So, after heavy regular drinking, if the flow of alcohol stops, the brain is left with out of control synaptic

  • firing with nothing to calm it down.

  • Now, you've heard of a drunk getting the shakes when they stop drinking. This is where that comes from.

  • Now, some drugs don't even bother imitating a neurotransmitter. Instead, they just screw with the levels

  • of natural neurotransmitters.

  • We're talking here about things like cocaine and methamphetamine and other amphetamines

  • like ecstasy and bath salts.

  • Cocaine is such an effective stimulant because it interrupts the reabsorption of dopamine and another

  • important excitatory chemical: norepinephrine.

  • By creating extremely high concentrations of them floating around in the synapses, nerve cells are

  • overstimulated and the user will feel pleasure from the dopamine and energy thanks to the norepinephrine.

  • But because it creates such a flood of these neurotransmitters the cocaine ends up depleting them,

  • and more and more cocaine is needed to produce the same high.

  • Now, the effects of smoking meth can last up to twelve hours versus one hour to cocaine and is vicious in it's

  • ability to create addiction.

  • Instead of blocking the re-absorption of dopamine, like cocaine does, meth causes the release of excess amounts of dopamine.

  • It's a nasty drug made worse by the fact that over time an addicts brain, in an effort of self-defense,

  • will eventually force neurons to release an enzyme that destroys all that extra dopamine,

  • as well as the brain's ability to produce more.

  • As a result, users will continue upping the dosage, seeking a high that they can't achieve.

  • Other new amphetamines bursting onto the scene including bath salts, which are so fascinatingly awful

  • that we did a separate episode just on them.

  • Bath salts contain a group of synthetic stimulants called substituted cathinones which combine the effects of

  • both cocaine and meth at the same time.

  • What scientists are now discovering is that these same chemical reactions brought about by substance abuse

  • are similar to those brought about by a number of behaviors, causing behavioral addiction.

  • Let's take gambling: the neural circuits manipulated by wagering money on blackjack, horse racing and other games of chance

  • are actually the same ones that originally evolved to help animals assess reward versus risk.

  • Like, you're living on the savannah and you haven't eaten in two days,

  • you don't want to be like, "I forget, is it the black berries that kill you or the red ones?"

  • But what researchers have discovered with gambling is that it's not only winning that enhances dopamine

  • transmission in the limbic system but it's also the near misses; it's the 4-out-of-5 jackpot symbols on the slot machine

  • or being one number off on the roulette wheel.

  • Those things actually have a larger effect on the brain than winning the jackpot.

  • Almost getting the reward causes strange things to happen to the ways in which your brain anticipates future rewards.

  • Our brains love to find and predict patterns. But, when it becomes fixed on predicting patterns in something

  • that's inherently unpredictable, like a slot machine, it leads to compulsive gambling.

  • And, in fact, in 2012, the Diagnostic Statistical Manual for Mental Disorders, which is pretty much the go-to

  • book for psychiatric illness professionals announced that it's going to add a new category for behavioral addictions

  • beginning with pathological gambling.

  • It's also adding references to internet and sex addiction for the first time and many would like to see food addiction added as well.

  • Food and sex addiction are controversial topics, partly because of the stigmas associated with them.

  • The release of dopamine as a response to eating fatty foods is completely natural and makes perfect sense evolutionarily.

  • However, even this natural release of dopamine can be exploited.

  • Studies of rats have shown that, when given easy access to high sugary and fatty foods like bacon and chocolate and cheesecake...

  • Ooh-mmm. Bacon chocolate cheesecake.

  • Those rats not only ignored their normal food but continued to eat the unhealthy snacks even when they were shocked in the process.

  • Over time, the rat's brains developed tolerance to the chemical response to junk food by desensitizing their

  • dopamine receptors, exactly like the hypo-functioning reward circuitry caused by drug addiction.

  • Findings like this have actually led to a theory that some people might have fewer dopamine receptors than

  • others, which may make them more predisposed to food and other addictions.

  • Like sex, for instance. This shouldn't come as a surprise, given that brain scans taken during orgasm closely

  • resemble those of heroin users after shooting up.

  • Like food addiction, sex addiction is linked to low dopamine levels in the brain which can lead to

  • post-sex hangovers that leave the addict in despair and on a quest to find his or her next fix.

  • It's a craving, both biologically and psychologically.

  • Even here on the internet our dopamine receptors are spoiled full of fun and stimulating distractions that activate our pleasure chemicals.

  • And like other addictive behaviors, it's often the anticipation that's greater than the reward.

  • I mean really, how many times did you check your email in the last hour and how many important emails did you actually have?

  • Meanwhile, studies of video gamers are showing that players will continue their gaming, even when multiple

  • distractions are placed in front of them.

  • Not that I would know anything about that.

  • We're living in kind of a golden age of brain research right now, which means that we're learning more about

  • the causes of addiction and possible cures every day.

  • And while there pretty much is no way to avoid overstimulating your dopamine receptors in this world of instant pleasures,

  • the rush of finding a particularly adorable cat on Reddit is likely going to remain my drug of choice,

  • at least for the near future.

  • Thanks for watching this episode of SciShow Infusion.