Serotonin may help prevent cocaine addiction. Only about 20% of people who use cocaine develop a severe addiction. A new study found that serotonin pushes back against the dopamine buildup that drives it. When the serotonin system is out of balance, that brake fails and addiction is more likely.
Summary: Cocaine is a strong upper, and people misuse it. But against common belief, it causes severe addiction in only 20% of users. So researchers knew the brains of these 20% must lack some kind of brake. Early studies proved that the brain’s dopamine reward path plays a key role in addiction. Dopamine that builds up in certain parts of the brain causes the high. It also helps lock in the memory of these experiences. In the new study, serotonin helped fight the addiction that dopamine buildup causes. In some people, serotonin is out of balance. This makes them prone to addiction. So fixing this serotonin imbalance may help people beat addiction.
Against common belief, studies show that just 20% of regular cocaine users get addicted. Most do have a mental dependence. But very few have so-called physical dependence1.
Psychological (mental) dependence is when a person uses a drug often because it brings pleasure. But the person can give it up without many health problems. In physiological (physical) dependence, a person may have severe withdrawal. That can make it almost impossible to give up the drug.
Dopamine and its brain paths sit at the center of addiction. Dopamine is a chemical that controls the activity of brain cells. When a person feels low, a small release of dopamine wakes up the brain and lifts the mood. Cocaine causes euphoria, or a high, by making dopamine build up in certain parts of the brain2.
Of all the brain centers, the limbic system plays a key role in addiction. It holds key memory centers, like the hippocampus and amygdala. These help people remember what brings pleasure. The limbic system is also rich in cells that make dopamine2.
Figure 1 Cocaine addiction, the role of dopamine and various brain centers2
Every system in the body stays in balance through two forces that push against each other. In the nervous system, some nerves speed up the heart and others calm it down. In the same way, some brain cells excite and others calm. So researchers knew the brain must have a brake on dopamine.
Early studies found that serotonin helps dampen many of dopamine’s effects. Doctors already use dopamine drugs to help people through withdrawal. Now researchers think drugs that raise serotonin may also help. They may fight the urge to use and help people beat addiction3.
Researchers tested mice to learn how serotonin may block cocaine’s pull. They also wanted to see how it cuts some harm from high dopamine. First, they taught mice to take cocaine. But after each dose, the mice got an unpleasant electric shock. By the end, 80% of mice stopped taking cocaine. Just like in humans, 20% kept going despite the shocks.
Next, they repeated the test in mice with a faulty serotonin transporter. Far more of these mice got addicted, 60%. But when the researchers gave these mice serotonin, the addiction rate fell back to 20%. So the test proved that serotonin is one of the main brain chemicals that block addiction1.
When a person takes cocaine, dopamine rises in certain parts of the brain. This causes a high and a feeling of pleasure. Sadly, the limbic system remembers this, which leads to using cocaine again and again. But serotonin acts as a natural balancer. It helps keep the brain from locking in these memories. So therapies that target serotonin may help prevent or beat addiction in many cases.
Frequently asked questions
Why is cocaine so addictive?
Cocaine makes dopamine build up in certain parts of the brain, which produces the high. The limbic system remembers what brought that pleasure. It holds memory centers such as the hippocampus and amygdala and is rich in cells that make dopamine. That stored memory is what pulls a person back to cocaine again and again.
Does everyone who uses cocaine get addicted?
No. Studies show that only about 20% of regular cocaine users develop a severe addiction. Most users have a mental dependence. They use it because it brings pleasure but can quit without many health problems. Few develop physical dependence. There, withdrawal gets so bad that quitting can seem almost impossible.
How does serotonin affect cocaine addiction?
Serotonin acts as a natural balancer against dopamine. It helps keep the brain from locking in the memory of the cocaine high. In mouse tests, 20% kept taking cocaine despite a punishment. In mice with serotonin transporter problems, 60% became addicted. Giving these mice serotonin brought the rate back down to 20%.
What neurotransmitter is most linked to addiction?
Dopamine sits at the center of addiction. The dopamine reward path drives the high and helps the brain store the memory of it. Serotonin is its counterweight. It limits several of dopamine’s effects. When serotonin is out of balance, a person becomes more prone to addiction. Researchers think drugs that raise serotonin may help fight the urge to use.
Related reading
Drug-seeking habits play a vital role in drug addiction · Ketamine for Cocaine Addiction · How Methylphenidate Works for ADHD · Drug Addiction Treatment, St. Louis
References
1. Li Y, Simmler LD, Van Zessen R, et al. Synaptic mechanism underlying serotonin modulation of transition to cocaine addiction. Science. 2021;373(6560):1252-1256. doi:10.1126/science.abi9086
2. Nestler EJ. The Neurobiology of Cocaine Addiction. Sci Pract Perspect. 2005;3(1):4-10.
3. R.B. R, B.E. B, M.H. B. Dual dopamine/serotonin releasers: Potential treatment agents for stimulant addiction. – PsycNET. Experimental and clinical psychopharmacology. Published online 2008. Accessed October 16, 2021. https://psycnet.apa.org/doiLanding?doi=10.1037%2Fa0014103