What’s New in Psychology?
Why Do Only One in Five Become Addicted to Cocaine?
Jim Windell
According to the American Addiction Centers, cocaine is a very addictive substance that can place you at risk for any number of health issues. Nonetheless, people begin using cocaine every day. And it is common for someone who tries it once to progress to regular, problematic use.
It’s estimated by the Substance Abuse and Mental Health Administration (SAMHSA) that there are 1.9 million cocaine users – many of whom are addicted.
But, can you really become addicted after one time?
The Center for Substance Abuse Research says yes; you can become addicted to cocaine, especially crack cocaine, the first time. It’s estimated that more than five million people in the U.S. use cocaine regularly.
Yet, researchers at the University of Geneva say that contrary to common thinking, cocaine triggers an addiction in only about 20 percent of people who try cocaine.
So why do some people use cocaine without becoming addicted while others get hooked on this drug?
Neuroscientists at the University of Geneva (UNIGE), Switzerland, developed a series of experiments that revealed a brain mechanism specific to cocaine. This mechanism is able to trigger a massive increase in serotonin in addition to the increase in dopamine common to all drugs.
The scientists first taught a large group of mice to self-administer cocaine voluntarily, and then added a constraint. Each time they self-administered cocaine, the mice received a slightly unpleasant stimulus (electric shock or air jet). Two groups then emerged. One group – 80% of the mice stopped their consumption – while the other group – 20% continued, despite the unpleasantness. The experiment was repeated with mice in which cocaine was no longer linked to the serotonin transporter, so that only dopamine increased when the substance was taken. In this second experiment, 60% of the animals then developed an addiction. The same was found in other animals with a reward system stimulation protocol that did not affect serotonin.
The results, published recently in Science, suggest that serotonin acts as an intrinsic brake on the over-excitement of the reward system elicited by dopamine, the neurotransmitter that causes addiction.
Christian Lüscher, a professor in the Department of Basic Neurosciences at the UNIGE Faculty of Medicine and the lead researcher, explains that when cocaine is consumed, two forces are at work in the brain. One force is dopamine, whose sudden increase leads to compulsion, and the other force is serotonin, which acts as a brake on compulsion. Addiction, therefore, occurs when an imbalance is created between these two neurotransmitters and dopamine overtakes serotonin.
“Actually, dopamine triggers a phenomenon of synaptic plasticity, through the strengthening of connections between synapses in the cortex and those in the dorsal striatum,” Lüscher says. “This intense stimulation of the reward system then triggers compulsion. Serotonin has the opposite effect by inhibiting the reinforcement induced by dopamine to keep the reward system under control.”
It is this compulsive behavior which defines addiction, which affects 20% of individuals, both in mice as well as in humans.
Apart from the increase in dopamine, each substance has its own specificity and effect on the brain. If the addictive effect of cocaine is naturally reduced by serotonin, what about other drugs?
The Geneva neuroscientists plan to next look at opiates – which are more addictive than cocaine – and ketamine, which is much less so. Their aim is to understand in detail how the brain reacts to these drugs and why some people are much more vulnerable to their harmful effects than others.
To read the original article, find it with this reference:
Li, Y., Simmler, L.D., Van Zessen, R., Flakowski, J., Wan, J., Deng, F., Li, Y., Nautiyal, K.M., Pascoli, V. & Lüscher, C. (2021). Synaptic mechanism underlying serotonin modulation of transition to cocaine addiction. Science, 373 (6560): 1252 DOI: 10.1126/science.abi9086
