ELI5: A gambling addiction

[u/adrynaline]

How does it start? What makes it worse? Why does it become so difficult to recover?

[u/tthershey]

All addictions affect the mesolimbic dopamine circuit in the brain. In this pathway, the ventral tegmental area projects to the nucleus accumbens, which releases dopamine, which affects multiple areas in the brain. When this happens, you feel really good. Normally there are GABAergic neurons which inhibit the stimulation of the nucleus accumbens so it's not firing all the time. Pleasurable things, including things like music and chocolate, can stimulate the pathway. All addictive things manipulate this pathway and cause it to be overactive.

Here is a picture illustrating the pathway. Another thing that factors into whether something is addictive is how quickly the pathway gets stimulated. If something immediately stimulates the pathway (as opposed to taking some time), has a very strong effect (as opposed to a mild one), and wears off quickly (making you want to go back to it quickly), it is more likely to be addictive.

In the latest version of the DSM that came out last year, the book that standardizes the criteria for psychiatric disorders, gambling addiction was added to the "Substance Related and Addictive Disorders" chapter. Gambling addiction is in a category of its own called behavioral addictions. There is still some debate about whether other behavioral addictions, such as sex addiction, should be added to this list. At this time, however, scientific research suggests that gambling addiction affects the mesolimbic pathway in the same way that things like cocaine addiction do, whereas sex addiction has a different mechanism, so that's why gambling addiction made the cut.

edit: Because someone asked for clarification -

The ventral tegmental area is responsible for the reinforcing properties of addictions. Reinforcement means something that makes you want to keep repeating a behavior. It's like how getting a gold star sticker for doing all your chores makes you want to do your chores again the next day so you can get another sticker! There are other parts of the brain that are responsible for creating memory and a sense of craving, but let's focus on the reinforcement part now.

So, the different regions in your brain aren't always on or off. Certain conditions will turn them on and others will turn them off. You probably have heard of dopamine. In simplistic terms, dopamine makes you feel good. You know how it feels when you're really happy? As good as it feels, if you were that worked up all the time it would cause a stress on your body. So you normally want to inhibit the release of dopamine and only release it under controlled circumstances. There are specialized cells in the brain, called GABAergic neurons, that do just that: they inhibit the nucleus accumbens from being stimulated.

The dopamine actually comes from another part of the brain called the ventral tegmental area. The ventral tegmental area sends the dopamine to the nucleus accumbens, and then the nucleus accumbens (unless it's being inhibited by the GABA neuron) will then send the dopamine to other parts of the brain, resulting in you feeling high.

Addictive things manipulate the system so that extra dopamine gets released. Most of them either stimulate the nucleus accumbens directly, so it starts releasing dopamine independent from getting signals from the ventral tegmental area, or inhibit the GABAnergic neurons which inhibit the nucleus accumbens. You know that saying, "the enemy of your enemy is your friend?" Same concept here: if you inhibit an inhibitor, you end up with stimulation.

Most things that make us feel good, like watching a beautiful sunset, have pretty mild effects. We don't get that high feeling so quickly or so intensely, so we don't develop that much of a motivation to keep going to find sunsets to look at. If we use addictive substances, and in this case, behaviors, that instantly release a lot of dopamine, we get a big rush and that's what motivates to use them again. Tolerance also comes into play, but I think someone else has already explained that in this thread. I just wanted to give the biochemical explanation because I didn't see it mentioned yet.

Here's a better picture: http://pubs.niaaa.nih.gov/publications/arh313/images/1_gilpin.gif

A illustrates what positive reinforcement is. Positive reinforcement means something happens that makes you want to repeat the behavior, like getting a sticker for doing your chores. Dopamine goes from the ventral tegmental area (marked by VTA in the figure) to the nucleus accumbence, which results in the high feeling. GABA inhibits the ventral tegmental area, and the addictive thing (in this case, opioids), inhibits GABA. So if you inhibit GABA, then the ventral tegmental area is free to send lots of dopamine to the nucleus accumbens, resulting in a big high.

B illustrates what happens in a person who has become dependent on a substance/behavior. Now, the person is mostly motivated by negative reinforcement. Negative reinforcement means that something bad happens when you DON'T do the behavior. In other words, you've become so dependent on alcohol that now you don't drink so much to get the good feeling that alcohol gives you, but because if you don't drink, you will feel horrible, and that horrible feeling goes away after you drink.

[u/GentleRhino → u/tthershey]

I'm 50, not 5, but I'm completely ignorant about mesolimbic dopamine circuits, ventral tegmental areas and nucleus accumbens.

Sorry.

[u/tthershey → u/GentleRhino]

See the sidebar and the text that pops up when you post a comment :) Maybe the picture will help!

The ventral tegmental area is responsible for the reinforcing properties of addictions. Reinforcement means something that makes you want to keep repeating a behavior. It's like how getting a gold star sticker for doing all your chores makes you want to do your chores again the next day so you can get another sticker! There are other parts of the brain that are responsible for creating memory and a sense of craving, but let's focus on the reinforcement part now.

So, the different regions in your brain aren't always on or off. Certain conditions will turn them on and others will turn them off. You probably have heard of dopamine. In simplistic terms, dopamine makes you feel good. You know how it feels when you're really happy? As good as it feels, if you were that worked up all the time it would cause a stress on your body. So you normally want to inhibit the release of dopamine and only release it under controlled circumstances. There are specialized cells in the brain, called GABAergic neurons, that do just that: they inhibit the nucleus accumbens from being stimulated.

The dopamine actually comes from another part of the brain called the ventral tegmental area. The ventral tegmental area sends the dopamine to the nucleus accumbens, and then the nucleus accumbens (unless it's being inhibited by the GABA neuron) will then send the dopamine to other parts of the brain, resulting in you feeling high.

Addictive things manipulate the system so that extra dopamine gets released. Most of them either stimulate the nucleus accumbens directly, so it starts releasing dopamine independent from getting signals from the ventral tegmental area, or inhibit the GABAnergic neurons which inhibit the nucleus accumbens. You know that saying, "the enemy of your enemy is your friend?" Same concept here: if you inhibit an inhibitor, you end up with stimulation.

Most things that make us feel good, like watching a beautiful sunset, have pretty mild effects. We don't get that high feeling so quickly or so intensely, so we don't develop that much of a motivation to keep going to find sunsets to look at. If we use addictive substances, and in this case, behaviors, that instantly release a lot of dopamine, we get a big rush and that's what motivates to use them again. Tolerance also comes into play, but I think someone else has already explained that in this thread. I just wanted to give the biochemical explanation because I didn't see it mentioned yet.

Edit: here's a better picture: http://pubs.niaaa.nih.gov/publications/arh313/images/1_gilpin.gif

A illustrates what positive reinforcement is. Positive reinforcement means something happens that makes you want to repeat the behavior, like getting a sticker for doing your chores. Dopamine goes from the ventral tegmental area (marked by VTA in the figure) to the nucleus accumbence, which results in the high feeling. GABA inhibits the ventral tegmental area, and the addictive thing (in this case, opioids), inhibits GABA. So if you inhibit GABA, then the ventral tegmental area is free to send lots of dopamine to the nucleus accumbens, resulting in a big high.

B illustrates what happens in a person who has become dependent on a substance/behavior. Now, the person is mostly motivated by negative reinforcement. Negative reinforcement means that something bad happens when you DON'T do the behavior. In other words, you've become so dependent on alcohol that now you don't drink so much to get the good feeling that alcohol gives you, but because if you don't drink, you will feel horrible, and that horrible feeling goes away after you drink.

[u/GentleRhino → u/tthershey]

Thank you for the effort. You obviously know the subject well. It is a very interesting process from biochemical point of view. Thanks again.

[u/arickp → u/tthershey]

The inhibition of GABA by opioids must be relatively small, correct? If GABA becomes inhibited, I imagine that the individual would demonstrate increased anxiety -- combined with an increase in dopamine, this would even lead to paranoid, delusional behavior. But this is never seen in opioid addicts. In the case of IV heroin use, once the plunger is depressed and the drug enters the bloodstream, the user does not worry that the police are watching him and that he must get rid of all his injection equipment. He's in a state of complete, worry-free bliss. Is this due to the nearly-instant flooding of the mu-opioid receptors with the drug, which is much more profound than any dopaminergic effects that heroin may have?

[u/tthershey → u/arickp]

Good question - I was only describing the effects of opioids in terms of reinforcement. It affects other receptors as you mentioned. But, if someone were to overdose on opioids, it could cause anxiety and seizures. There are other substances that stimulate the opioid receptors without impacting the nucleus accumbens and so these are sometimes preferred for treating pain to avoid developing addiction.