Drug Addiction: A Chronic Disease
The debate surrounding drug abuse’s definition has been going on for many years. Although many psychiatrists claim that it is only a psychological problem, several neurobiological theories highlight the impact of drugs on our system1.
In the United States alone, nearly 10% of people over the age of 12 are addicted to alcohol or other drugs. Substance abuse represents a market of more than $700 billion annually, so it has an absurd impact on the economy2.
Even with all the social and biological impact, there is no unanimous consensus on labeling drug abuse. Let’s take a step-by-step look at what happens in our bodies and brains once illicit use begins, and why science has a basis for considering it a chronic disease.
The Toxic Union
We all know that drugs (which are addictive) activate specific sectors in the brain that cause the release of dopamine3. This is a neurotransmitter that generates positive stimuli on receptors that generate a reward response and cause conditioning.
This is a whole closed cycle. The more exposed you are to dopamine, the more stimuli you will cause. However, your cells become more resistant to stimulation with each dose of dopamine4. Now you need even more dopamine to create the same response.
Also, when your body has low concentrations of the neurotransmitter (when you are not on the drug), it will start to “ask” for it. Your cells will launch an anticipatory response that is what we know as “craving”.
This is where the real problem with the rest of the theories occurs. The conditioning that makes drug addiction a chronic disease is part of a biological problem: dopamine. Not only are there changes in your mind (because you want more drugs now), but there are changes in your cell receptors, the number of neurotransmitters, nerve connections, etc.
What happens in Neurons?
After starting to take drugs, neurons change, like everything else in our body. We are beings of adaptation, so we are constantly changing even at a molecular level to continue living.
Scientifics call the effect that occurs in the neurons Neuroplasticity5, specific changes in the way the neurons communicate with each other and the environment they used to do so.
Don’t think this only happens when you are exposed to drugs. As we said earlier, our bodies are designed to adapt. When you learn or try to improve your memory, the first changes that occur, biologically, are in the neurons.
The problem is that things can get a little confusing when using drugs. A response that should only occur when you are learning or enhancing your memory becomes triggered by an illicit substance. This only causes the two mechanisms to become confused6.
Now, neuroplasticity gives way to your brain understanding -biologically- that using drugs has been a learned and useful response for many years (since it alters the way we process memory).
When you record something in your brain with neuroplasticity, the stimuli are stronger. Remembering your mom evokes a powerful stimulus, compared to remembering what you did yesterday at 8:59pm. What do you think happens with drugs?
That’s right. The changes on each of the neurons disrupt all these signals, and now we’ve created a terrible link. Now, every time you consume, powerful stimuli will be sent to your memory, which only promotes prolonged consumption.
It’s as if you’re under exposure to a virus, like the flu. It will enter your body, create changes within it, and then snot, malaise, and fever will follow.
We can see the changes that the drugs create in key regions of our brain. Remember that neurons are in the entire central nervous system. The alterations caused by these substances can reach the cerebral cortex, the limbic system (emotions and desires), the dorsal striatum (in charge of habits and routines), the hippocampus (memory) and the prefrontal cortex (our self-regulation)7.
The impact on these specific areas of the brain, through neuroplasticity, is what creates a complete response involving over one specific system. Not only do you have the biological damage caused by the drug, but you learn to need it (hippocampus), desire it (limbic system), make it part of your life (dorsal striatum) and let it control you (prefrontal cortex)
Could we say it’s just a learned response? Is it just a change in behavior? Is there nothing biological to make us think it’s a chronic disease?
Not everyone is at the same risk for drug addiction. We are not talking about social factors (such as living in a dangerous low social stratum where drugs are handled), but about biological changes.
For example, a person with family members who has cancer is also likely to have cancer. If you are likely to be obese, you will be more likely to have diabetes. These are classic risk factors for any chronic disease.
The same is true for drug addiction8. Not everyone has the same susceptibility (for genetic, environmental, and development-related factors). This not only determines the first use, but the sustaining and subsequent changes related to neuroplasticity.
- Nora D. Volkow, M.D., George F. Koob, Ph.D., and A. Thomas McLellan, Ph.D. Neurobiologic Advances from the Brain Disease Model of Addiction. N Engl J Med. 2016 Jan 28; 374(4): 363–371. doi: 1056/NEJMra1511480
- Results from the 2013 National Sur-vey on Drug Use and Health: summary of national findings. Rockville, MD: Sub-stance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality, 2013. Google Scholar
- Di Chiara. Nucleus accumbens shell and core dopamine: differential role in behavior and addiction. Behav Brain Res. 2002 Dec 2;137(1-2):75-114. DOI:1016/s0166-4328(02)00286-3
- Schultz W. Getting formal with dopamine and reward. Neuron. 2002 Oct 10;36(2):241-63. DOI: 1016/s0896-6273(02)00967-4
- Kauer JA, Malenka RC. Synaptic plasticity and addiction. Nat Rev Neurosci. 2007 Nov;8(11):844-58. DOI: 1038/nrn2234
- De Roo M, Klauser P, Garcia PM, Poglia L, Muller D. Spine dynamics and synapse remodeling during LTP and memory processes. Prog Brain Res. 2008;169:199-207. DOI: 1016/S0079-6123(07)00011-8
- Volkow ND, Morales M. The Brain on Drugs: From Reward to Addiction. Cell. 2015 Aug 13;162(4):712-25 DOI: 1016/j.cell.2015.07.046
- Demers H. The Genetics, Neurogenetics and Pharmacogenetics of Addiction. Curr Behav Neurosci Rep. 2014 Mar 1;1(1):33-44. DOI:1007/s40473-013-0004-8