Drug use leads to increased dopamine and glutamate, which causes alterations in the reward circuit of the brain, increasing synaptic plasticity, and reinforcing that drug use[1]. Addiction literally rewires the brain. Now it kind of makes sense why every adult is so scared of kids using drugs in high school and college. But at the same time, if we know addiction impacts our brain, it doesn’t make sense why society shames addiction as a personality fault and a choice, instead of a brain health disorder. Let’s look more into the neuroscience of how exactly drug use and addiction impacts the brain to see if it’s really as scary as everyone says, and if it really is a choice.
Neurotransmitters
Psychostimulents also increase the neurotransmitter dopamine. This happens when the drug binds DA receptors, increases the release of dopaminergic neurons, reduces reuptake, or decreases the enzyme that degrades dopamine[1].
Reward Circuit
Dopamine plays a crucial role in the reward pathways of the brain, especially in relation to drug use. It causes drugs to be rewarding. The brain gets more and more addicted to dopamine, craving more and more of the drug[1].
When drug use increases dopamine in the brain, the reward circuit causes the brain to build up a tolerance to the drug. This is dangerous with addiction, especially when the tolerance is environment specific. Specific environments can be associated with anticipation of drug use, increasing tolerance. But when using drugs not in that environment, tolerance is not as high, and overdose can occur[2].
Tolerance can also be dangerous in relation to glutamate’s role in the brain’s learning and memory processes.
Neuroplasticity
Glutamate is related to long-term potentiation, the strengthening of synapses in the brain.
This means that with drug use, the brain’s extra dopamine makes drugs extra rewarding. But the extra glutamate changes the brain’s natural firing pattern, making the brain expect drugs. It makes drug use and the effects of drugs the norm for the brain. The glutamate helps the brain learn and remember how much it likes the drugs. This increase in long-term potentiation that happens with drug use is accompanied by a decrease in long-term depression[3].
Long-term depression, a decrease in synaptic strength, in the prefrontal cortex is decreased in addiction, which reduces the inhibition and control over drug use[3].
It is interesting to note, that one of the ways neuroplasticity works in the brain is glutamate synapses onto dopaminergic neurons in the ventral tegmental area[1]. This makes sense then, why a drug impacting dopamine, also impacts glutamate, and vice versa.
Repeat
This is why addiction has such a high risk of relapse. The brain is rewired to learn and remember that drugs are rewarding. And the brain has less control over it with time[3].
Brain Health
So drug use and potential addiction is scary. It rewires how the brain is rewarded, how the brain learns and remembers, and how much impulse control the brain has.
But addiction is also less of a choice than society makes it seem. One could argue that after the first time an addict uses substances, they are no longer choosing, and have become a victim of their brain. There is also the argument that the first choice to use drugs is also not a choice, but a culmination of genetic and environmental factors [4]. Regardless of how much of drug use is a choice, addiction is not. The science says that addiction causes the brain to be rewired, and usual choice making processes are impacted. Addiction is a matter of brain health, just like any other physical disorder.
References
[1] Mozafari, R., Karimi-Haghighi, S., Fattahi, M., Kalivas, P., & Haghparast, A. (2023). A review on the role of metabotropic glutamate receptors in neuroplasticity following psychostimulant use disorder. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 124. https://doi.org/10.1016/j.pnpbp.2023.110735
[2] Sinha, R. (2008). Chronic stress, drug use, and vulnerability to addiction. In Annals of the New York Academy of Sciences (Vol. 1141, pp. 105–130). Blackwell Publishing Inc. https://doi.org/10.1196/annals.1441.030
[3] Robinson, T. E., & Kolb, B. (2004). Structural plasticity associated with exposure to drugs of abuse. Neuropharmacology, 47, 33–46. https://doi.org/10.1016/j.neuropharm.2004.06.025
[4] Gerring, Z.F., Thorp, J.G., Treur, J.L. et al. The genetic landscape of substance use disorders. Mol Psychiatry 29, 3694–3705 (2024). https://doi.org/10.1038/s41380-024-02547-z
