How / why does the body become physiologically dependent on a substance?
What happens to our bodies to create a physical substance dependence? Like the only way to prevent someone in severe withdrawal from dying is to give them more of the substance they are addicted to? It seems obvious to me that dopamine/serotonin etc have their effects in psychological dependence but shouldn’t our bodies react more positively to not being regularly hit with what is basically a poison/s?
In: Biology
Let’s take alcohol as an example. Alcohol imitates a chemical that the nerves in your brain use, called GABA. What GABA does, basically, is tell nerves to chill out. (It’s an “inhibitory neurotransmitter”; it tells nerve cells to fire less.)
If you’re a very heavy drinker and have lots of alcohol in your system all the time, your nerves learn to pay less attention to GABA — because the alcohol is doing GABA’s job and more. You don’t need to tell your nerves to chill out, because they’re already drunk.
But then if you *stop* taking alcohol, now your nerves run too hot! The job that GABA is supposed to do — get your nerves to chill out — *isn’t getting done.* As a result, your nerves fire too much, making you shake, sweat, hallucinate, and even have seizures. This is *delirium tremens* (“the DTs”) and it’s one of the worst symptoms of acute withdrawal from high alcohol intake.
So physical dependence on alcohol is due to your brain adjusting to having alcohol all the time, and becoming less able to chill itself out *without* alcohol.
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