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Psychology
The Neuroscience of Addiction
How the Reward System Is Hijacked
Related Worksheets
Addiction is a chronic brain and behavior disorder in which a person continues using a substance or behavior despite harmful consequences. It matters because it affects learning, motivation, decision making, health, families, and communities. Neuroscience shows that addiction is not simply a lack of willpower, but a change in how brain circuits assign value and drive action. The reward pathway is central because it helps the brain learn what is important for survival.
Key Facts
- The reward pathway includes the ventral tegmental area, nucleus accumbens, prefrontal cortex, amygdala, and hippocampus.
- Dopamine helps signal reward prediction and motivation, not just pleasure.
- Many addictive drugs cause dopamine release that is stronger or faster than natural rewards such as food or social connection.
- Tolerance means a larger dose is needed to get the same effect: response decreases as repeated exposure increases.
- Withdrawal happens when the brain has adapted to a drug and then must function without it.
- A simple risk model is addiction risk = exposure x vulnerability x environment, where genetics, stress, age, and access can all change vulnerability.
Vocabulary
- Dopamine
- Dopamine is a neurotransmitter involved in motivation, learning, reward prediction, and movement.
- Reward pathway
- The reward pathway is a set of brain circuits that helps reinforce behaviors linked to survival and important goals.
- Tolerance
- Tolerance is a reduced response to a substance after repeated use, often leading a person to take more to feel the same effect.
- Withdrawal
- Withdrawal is the set of physical and emotional symptoms that can occur when a dependent brain and body no longer receive a substance.
- Craving
- Craving is a strong learned urge to use a substance, often triggered by stress, cues, memories, or withdrawal.
Common Mistakes to Avoid
- Thinking dopamine equals pleasure only is wrong because dopamine also teaches the brain what to seek and what cues predict reward.
- Calling addiction only a bad choice is wrong because repeated drug exposure can change brain circuits involved in impulse control, stress, learning, and motivation.
- Assuming tolerance means the drug is safer is wrong because tolerance can lead to higher doses, while overdose risk may still remain high.
- Expecting willpower alone to cure addiction is wrong because cues, withdrawal, stress, and altered reward circuits can overpower short term intentions without treatment support.
Practice Questions
- 1 A drug increases dopamine signaling in a reward circuit from a baseline value of 20 units to 90 units. What is the increase in units, and what percent increase is this relative to baseline?
- 2 A person originally feels strong effects from 10 mg of a substance, but after tolerance develops they need 25 mg for a similar effect. By what factor did the dose increase, and what is the percent increase?
- 3 Explain why a person in recovery might experience intense craving when passing a place where they previously used a drug, even if the drug is not currently in their body.