What makes something addictive? Are ADHD drugs addictive? What about sugar?

“I’m going to head to Tim Horton’s for a coffee.”

“Sure, no problem.”

You walk to Tim’s and you begin to realize you’re hungry. It’s 11:45 AM and lunch is only fifteen minutes away. You’ve brought your lunch to work today as well so you should be good.

Just a coffee, you say to yourself.

“Hi, welcome to Tim Horton’s! May I take your order?”

“Hi, yes I’ll have a large coffee with milk, a vanilla dip doughnut, and a pack of those doughnut sticks you have.”

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What is it that makes fried, sugared dough addictive? Or deep-fried potatoes? Or sour patch kids? Or anything, for that matter?

In our brains, there exists something called the nucleus accumbens. This part of the brain is known as the reward centre. What does this mean? Every time you do something that feels good, this centre “pings,” and makes you feel good. Why does this part of the brain exist? Well, it’s actually essential to our survival! Things like eating, drinking water, and having sex, are vital biological functions for our species. Without them, we would not survive. Very few of us, however, are thinking about, “I need to survive and propagate my genes,” as we eat and have sex. No, most of us do these things because they feel good. That’s where the nucleus accumbens comes in. It pings and rewards us with a shot of dopamine, the brain’s “happiness chemical,” when you do something that’s good, biologically. It’s a built-in incentive system to ensure we are doing, and feel good about doing, those functions essential for species survival.

This system, however, is imperfect, and it is prone to being hijacked. The nucleus accumbens is where many substances of abuse act, including cocaine, crystal meth, and any number of drugs. This is why many people with drug addiction become very skinny, and can waste away. The drugs hijack the system, and reward you more than food. Drugs steadily train the brain that the best rewards come from the drugs, and not food or water or sex. A great example of how strong the craving for drugs can be is a study that examined rats, who had electrodes placed in their brain at the site of the nucleus accumbens. The rats were given the ability to hit a button in their cages, which would activate the electrode, stimulate the nucleus, and cause a reward. The rats eventually choose to die while hitting the button, and totally neglect vital functions such as eating and drinking.

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But what is it that makes a substance addictive? Sugary foods can be addictive and cause cravings, for example, while carrots almost certainly do not. Cocaine and crystal meth are extraordinarily addictive drugs, while ritaline and vyvanse, medications for ADHD which act similarly, are not. What is responsible for this difference?

We think we know!

The nucleus accumbens appears to be sensitive the the size of a potential reward. Finding a penny on the ground, for example, makes us feel a lot less better than finding a one hundred dollar bill. Biologically, this discrimination has allowed the brain to prioritize eating high caloric foods, over low caloric foods, although both may taste good. (This function would have evolved prior to the food-availability we experience today in the Western world – the drive to eat higher calorie foods is a clear disadvantage to many of us nowadays.) The same principle applies today, which is why sugary, fatty foods are so addictive. The sugar and the fat, the nutrients essential to life which are activating the nucleus accumbens in the first place, are higher in doughnuts than they are broccoli, and therefore we crave doughnuts. This is actually a great example of how the advantage of a particular behaviour, and whether it is a mental illness, depends entirely on context. A drive to eat high caloric foods would have previously been evolutionary essential – now it causes heart disease.

So what’s the deal with drugs?

Well, the same principle applies. The strength of a stimulus is directly proportional to how addictive the substance is. So what affects the strength? Food that are higher in sugar and fat cause a higher level of nucleus stimulation, therefore we crave food that are slowly killing us. This is also true for drugs of abuse; crystal meth is several orders of magnitude stronger than cocaine, and meth is a hell of a lot more addictive. But there’s more! The speed of the stimulus also matters!

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When a sugar/fat/drug reward is given to us suddenly, the nucleus reacts more strongly to it, and we get a higher reward. This also reinforces the strength of an addiction. This has implications for food, which is why a banana and a candy with the exact same amount of sugar make us feel differently. The candy which instantly digests and gives us a sudden jolt of sugar, is highly addictive. The banana, which takes time to digest and releases the same amount of sugar, just over time, is not addictive!

This principle also applies for drugs, and gets to the root of why ADHD medications are not addictive – usually. The medications used for ADHD tend to digest very slowly, and although they act on the brain in the exact same way as cocaine and crystal meth, are not addictive. This is because that, relative to drugs of abuse, the medications are released very slowly.

The exception can be if you use ADHD medications in ways they are not meant to be – such as snorting or injecting (neither of these are safe methods to use). By snorting/injecting, instead of digesting you get around the bodies need to digest, and you can get a sudden jolt of dopamine, which would potentially contribute to an addiction.

Dr. Travis Barron is a resident physician in Toronto, Canada.

Can you develop ADHD?

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Andrew was always a high achiever. He got straight A’s in high school, was valedictorian, and assistant captain of the basketball team. Andrew would often spend long evenings on the weekdays and even some of the weekends studying. His parents reassured him he was developing good habits.

When Andrew was 17, he graduated high school, and started university. As in high school, he spent much of his time studying. He put considerable effort into his academics. Unfortunately, a few weeks into his first semester, Andrew forgets to hand in a major project. A few weeks later, he doesn’t do well on a test. Andrew begins to panic and decides to see his doctor.

“Doc, there’s something happening to me.”

“What makes you say that, Andrew?”

“I think my brain is… failing or something. I’m struggling so much at university and I never had any trouble in high school at all…”

Attention-deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that affects attention. You can read more about ADHD here. What does neurodevelopmental disorder mean? In general, this term refers to any problem which may arise during brain development. While brain development occurs to some extent throughout our lives, the major development of the brain happens while we are still a fetus! This means that our understanding of ADHD is that it develops before we are born, as a result of numerous genetic, environmental, intrauterine factors.

Andrew might have ADHD. So how does that make sense, given what we know about ADHD? If ADHD exists from birth (probably), how is he only having problems now?

What Andrew is describing may be what is known as adult ADHD. What is adult ADHD? Well, it’s the same as ADHD! And it’s also present from birth. The only difference between adult ADHD and ADHD is that adult ADHD has been, until adulthood, undiagnosed, for a variety of factors.

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ADHD screening is usually initiated by primary grade school teachers. Sometimes I meet kids from lower serviced neighbourhoods and poorer schools that simply were not given the opportunity to be screened as a child. I meet kids who were recommended to be screened as a child by their teachers, who have parents which declined the screen for any number of reasons, including not believing in ADHD and religion. I often meet women (and some men) who have gone undiagnosed, despite having struggles with academics when they were younger, because they have the “less obvious” inattentive subtype (previously known as ADD). Other times, I meet children who have been able to compensate for their natural attention abilities in their brain, for example by excessive studying (4+ hours a day in some cases) and who have flown under the radar. These kids often run into problems as they move through the academic system and the demands of the program exceeds their ability to compensate.

Andrew is an example of one of these children. He was likely able to compensate for a naturally lower attention span/hyperactivity in high school, and these coping strategies were likely overwhelmed when moving to post-secondary. Features of ADHD in adults can include mood swings, impulsive anger, losing keys, forgetting appointments, trouble holding down a relationship, and trouble holding down a job. Fortunately for Andrew, medications for ADHD are 85% effective, among the most of any drug! Ever.

So did Andrew develop ADHD? No. ADHD is a neurodevelopmental disorder, and is (in all likelihood) present since birth.

Editor’s note: There are however other illnesses which can affect attention which can develop later in life. Depression and anxiety, for example. One thing that is not ADHD, which I often see college age kids asking about, is marijuana. Marijuana interferes profoundly with attention is my most likely suspect when a marijuana user presents with new symptoms of inattention.

Dr. Travis Barron is a resident physician in Toronto, Canada.

Does ADHD exist?

“Based on all of the information you have provided, the collateral information, and the report cards, I think the most likely explanation is Attention-Deficit/Hyperactivity Disorder, also known as ADHD.”

“The doctors tried to diagnose me with that when I was a kid, and now you want to medicate my kid? I don’t believe in ADHD, we’re getting out of here.”

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It’s not an uncommon scenario. A parent brings their struggling child into my office for an assessment. The child promptly runs into my office, and immediately begins playing with the toys laid in a bin by my desk. Mom continually redirects the kid, who for some reason, just can’t seem to sit still. “He’s run by a motor,” she says, “he’s always been this way, full of life! But he’s really struggling at school.”

Attention-Deficit/Hyperactivity Disorder is a real disorder, that in broad strokes, can present in two different ways. There is the hyperactive sub-type, which is probably what most of you picture when you think of ADHD. Less recognized is the inattentive subtype of the illness, previously known as ADD. These are people and kids who can zone-out and have trouble maintaining attention, but are not running around the classroom (as a clinical pearl, women tend to present with the inattentive sub-type, and males with the hyperactive).

So what is ADHD, other than a hyper kid? To understand that, we must first understand what are psychiatric diagnoses. You can read more about that here. The punchline is that a feature of personality, behaviour, or mood, only becomes an illness when it begins to interfere with functioning. If you’re an anxious person, that can be a source of strength. It makes us on time for work, helps us meet deadlines, and not forget our wedding anniversary. If your anxiety gets to the degree it begins to cause avoidance and problems functioning (for example, anxiety causing you to miss work), then you would meet criteria for an anxiety disorder.

There is a similar phenomenon with ADHD (which *disclaimer* remains poorly understood!)


Our attention span lives in our frontal lobe, the front part of the brain. If we took one hundred people and tested their attention span, it’s likely we would find a range of different attention spans among the population sample. If we plotted this on a graph, it would likely look something like the picture to the left. Attention span would be on the x-axis (bottom), and the number of people with that attention span on the y-axis (side). Note that the numbers contained on the graph in this post are meaningless and are just for understanding!

A quick interpretation of the graph allows us to arrive at some conclusions. Most people have an average attention span, represented by the peak in the graph. Some people have a superior attention span, the plateau on the right side of the graph. The plateau on the left would be those with poor attention spans. So in summary, there exists a spectrum of attention spans, with most people falling near the middle, with some people (outliers) on the edges.

Credit: Medicalnewstoday

The prevalence of ADHD is between 5-10%, meaning 5-10% of the population have ADHD. These individuals would be represented on the graph by the lower attention span outliers, about from the “-2” on the x-axis above to the left limit of the graph. But does having a low attention span mean you have ADHD?


Remember, context is always important in psychiatry! If something does not interfere with your functioning, it’s not a disease, it’s just who you are. Our society has, over time, placed increasing emphasis on an education model focused primarily on sitting in a seat. A math test is in many ways as much a test of your ability to sit still for an hour straight as it is about your skills in math. The modern day office is in many ways a person with ADHD’s nightmare. If you take the same child and place them in a playground, a gym, or a more active form of education, you may find they excel. Many of the people diagnosed with ADHD today may find they did not qualify for the diagnosis one hundred years ago, when time spent at a desk was minimal. All of that to say, ADHD exists, and is a result of the direct interaction between our individual attention spans and societal expectations!

So do we medicate these kids, if a change in environment can sometimes optimize functioning? That’s a complicated question. The answer is (usually) yes. The impairments in functioning caused by ADHD can be life changing. Academic and vocational success may depend on it. Happiness in relationships, impulsive anger, and substance use, are all impacted by treated/untreated ADHD. The reality is our ability to change the environment in our regulated world is extraordinarily limited. The fact is we are all expected to graduate high school, and that’s that. While some parents find success for their children in alternative school systems with different education models, in my experience this has a limited benefit.

It’s not all doom and gloom. Treatment for ADHD is 85% effective, among the highest response rates for any medication for any illness. Ever.

I recently met a middle aged man presenting with problems losing things. He was worried he had dementia. This man worked as a camera man for an international news agency, and his work brought him all over the globe. He has worked in countless battlegrounds, war torn countries, and environments on earth that I cannot begin to imagine. And he excelled at his job. On further history, outside of occasionally losing his keys, the remote, or his cell phone, he wasn’t really having any issues. He had many of the features of ADHD and may very well have met criteria for the illness, particularly when he was school-aged, based on his old report cards which he brought in at my request. This man, however, had found a partner and an occupation which were not only tolerant of this mans attention span and resultant behaviours, but embraced it.

“So doc, do you think I have ADHD?”


Editor’s note: Often times I meet people who later in life, after high school and college, find a niche job that works for them and they can reduce or even eliminate the need for medications. If your child is struggling in school due to ADHD, I highly recommend treatment, because it can have life changing consequences!

Dr. Travis Barron is a resident physician in Toronto, Canada.