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What is addiction and what causes it?

Credit to Freestocks, via Unsplash

Disclaimer: the experiences of addicted people are extremely complex and cannot be appropriately covered in this post. This is just a brief review of where science is at this point and it doesn't necessarily match the feelings of people with an addiction problem. Addiction many times has a lot of emotional layers behind it that make it ever more complicated to exit from it. However we may choose to define addiction, addicts should be treated with empathy, in treatment centres and in society. I believe addiction can be a way to cope with other complicated situations that the person has gone through and that these should be appropriately addressed so that an addict can recover. In no case should they be dismissed as weak or superficial people that don't deserve help.

Addiction has always been a controversial topic. Many people think addicts are weak people that succumb to immediate pleasure even though they know that it will have negative consequences later on. They think that this is an “antinatural” behaviour when in fact it is quite normal. It is called “delay discounting” and we all do it. It means that we take away value from a certain reward the further away it is. So if we have to chose between two rewarding experiences and one is further in the future, we are more likely to choose the one that is readily available (for example, drugs) than the one further away. But have our prejudices against addicts hindered their recovery?

There are two main questions that are essential in addiction research that once answered might help the development of directed treatment options. The first one is more complicated than it may seem, but crucial if we want to understand addiction: what is addiction in the first place? The second one is, in my opinion, equally complicated: what causes addiction?

1. What is addiction?

Let’s start with the first one. For decades many people thought (and many still think) that addiction is a voluntary behaviour, a free choice. However, science has proven that there is not a lot that is voluntary about addiction. It wasn’t until the 90s that scientists started to defend the position that addiction is a disease and not a choice, and that, therefore, addicts need treatment to overcome it. This idea stems from the fact that several brain structures change in the brain of an addict compared to the general population. These changes range from very small changes, like gene expression, which we cannot directly visualize, to big changes that are visible to the “naked eye”, such as changes in the size of specific brain structures involved in judgement and motivation. Because there are physical changes in the brain and addiction has negative consequences for the individual and for society, scientists have termed addiction a disease.

However, this disease starts with a voluntary action. Shouldn’t this make us think that addiction is not a disease, but a very difficult habit to break? Some scientists, like Dr Marc Lewis, believe so. One of the main arguments in this line of thinking is as follows: we know diseases can produce changes in the brain, but changes in the brain also occur with any learned behaviour. Therefore, changes in a brain region cannot be directly equated to brain disease. A very famous example is the case of the London taxi drivers, who have to learn the road distribution in London by heart. They, in turn, have a very large hippocampus (the region in charge of spatial memory in the brain) compared to people with other jobs. You can see the full explanation of this position in the following YouTube video:

But ultimately, why is the definition of a concept important? As long as we know how it works biologically, it should be enough, right? Well, this is not entirely correct. Healthy and sick people live within society, and, therefore, what the general public thinks of addicts influences what options are acceptable and available for treatment. For example, AIDS has been one of the most devastating epidemics in human history. However, most of the people affected by it were groups rejected by society, such as gay men or heroin addicts. Therefore, the interest in this disease and the resources for researching the evolution of HIV and treatments against the virus were meagre for a long time. Addicts are generally a rejected group. If the rest of society (and even themselves) think that they are just weak people that cannot make the resolution to stop their addictive behaviour, there will be no treatment and they will be left to fend for themselves. So is thinking that addiction is a disease instead of a choice a better approach?

Some researchers defend that talking of addiction as a disease passes a message onto the “patients” that is as harmful as the free choice belief. Being a patient seems to imply that addicts are victims and that they can only get cured by a pill. It takes away the power to treat themselves by changing the patterns that lead to addictive behaviour. However, the fact that addiction is a brain disease doesn’t mean that addicts should perceive their situation as unsolvable without a pill. Other diseases can also be treated (at least partially) without a little magic pill, and people are prescribed exercise or a special diet to treat it. The definition of disease is a biological state that deviates from the normal functioning of the body, causing distress to the person suffering it, their immediate circle, or society. We could say that addicts tick these boxes: the brains of addicts function and look different to what the brains of the average population look like. It is true that the parts that are altered have to do with decision making, so these changes could be related to a detrimental habit. However, these new habits cause distress to both the person directly affected by addiction and their surroundings. Therefore, by this definition, we could say that these habits are pathological. Unfortunately, it is clear that no magic pill will release addicts from their situation easily or quickly. But since, if we accept that addiction is a disease, it would be a mental disorder, we could hypothesize that other non-"strictly biological" strategies might work as a treatment, for example, cognitive therapy.

2. What causes addiction?

Nonetheless, we need to know what is at the root of the habit/disease to be able to successfully help addicts exit their adverse situation. Treatments that are designed without the root cause of a disorder in mind might help with the symptoms but won't eradicate the disease and patients could consequently have a relapse.

Unfortunately, there is no clear answer to this question. As with many psychiatric disorders, finding the cause for addiction has proven very hard (remember that psychiatric disorders are born from a combination of genetic and environmental factors that can be combined in many ways with similar outcomes). However, a common factor we see in addiction patients and in patients from other psychiatric diseases is loneliness. Why loneliness is a good candidate as a major risk factor for addiction is beautifully explained in the podcast “Your Undivided Attention” by Tristan Harris and Aza Raskin. Listen to the full podcast episode here:

I’ve taken some of their examples to quickly explain it here. In Britain, people that need painkillers at the hospital are often treated using a very pure version of heroin, which is one of the most addictive drugs that exist. However, these people don’t necessarily become addicted to the drug. This rules out a hypothesis that was sustained for many years also in the scientific community: addiction can’t be caused just by the chemicals from the drug. Additional evidence for this is that certain behaviours, such as gambling and watching porn, can also be addictive.

Credit to Markus Piske via Unsplash

But this doesn’t automatically link addiction to loneliness. There are other clues that lead to this conclusion, though. First of all, when you put a rat alone in a cage and let it choose between a bottle of plain water and a bottle of water with heroin, it will undoubtedly choose the water with heroin and almost always kill itself by overdosing. But if you put a group of rats in the cage with all the environmental stimulants rats are happy with and give them the same choice, they will not drink excessively from the heroin bottle and they don’t overdose - this of course also points at the artificial way in which we reconstruct the natural environments of animals in the lab and calls into question the experimental set-ups that are used. That is another topic though, which needs to be addressed properly in a separate post, so let's continue with the topic of addiction.

Keep this experiment in mind while we look at the way Portugal handled their drug addiction problem. In Portugal, around 1% of the population was addicted to drugs. They initially took the same “drug treatment” approach many countries still practice: they imprisoned drug addicts or forced them into treatment centres, etc. However, the number of addicts wasn’t decreasing and it was still an important burden on Portuguese society. The government then decided to ask a group of expert scientists for help. When the scientists came back with what they thought was the best solution they said: we want to decriminalize all drugs and invest the money that is currently used to imprison drug addicts and use it for a dramatically different approach. We want to offer psychological support to addicts and we want to implement a programme of reconnection. With that money, the government promoted the hiring of drug addicts in jobs they were passionate about or offered micro-loans so that they could start their own business. The rate of addiction went down dramatically, it was the largest decrease in the world. No one wants to go back to the previous system. So could reconnection be the treatment for addiction? It is unlikely that this is the sole explanation to why people develop addiction, but it seems like a good bet until we delve deeper into other factors that also contribute to someone becoming addicted.

Why is it important that we find the root of addiction and any other psychiatric disorder? As I stated above, treatments that scratch the surface of the disease don't really cure the illness, they just relieve some of the symptoms. Therefore, patients could have a relapse or might depend on a particular medication for the rest of their life. They will never recover completely because the root of the problem is still there.

If loneliness is at the root of (some) psychiatric disorders, we might be in a tricky situation. We live in a society that is ever more focused on digitalizing everything, effectively reducing human connection. However, this might not be the smartest move if loneliness really is a key player in psychiatric disorders. You can read more about social media and depression and suicidal ideation in my previous post and on Dr David Puder's podcast.

So the big question is, are we prepared to make the sacrifice of controlling our social media use to preserve our mental health, or will we continue to abuse it in detriment of our physical interactions and our mind?


- Leshner, A. I. Addiction Is a Brain Disease, and It Matters. Front. Neurosci. 278, (1997).

- Wise, R. A. & Koob, G. F. The development and maintenance of drug addiction. Neuropsychopharmacology 39, 254–262 (2014).

- Volkow, N. D. & Morales, M. The Brain on Drugs: From Reward to Addiction. Cell 162, 712–725 (2015).

Laura Sotillos Elliott
Laura Sotillos Elliott
Read next: Never In the Cover of Night
Laura Sotillos Elliott

Future doctor. Interested in science communication in all its forms: writing, podcasting, organizing scientific events...

Follow me on twitter at @addict_science

See all posts by Laura Sotillos Elliott