A Complex Yet Crucial Chemical: Exposing Myths About Dopamine

Dopamine seems to be ubiquitous. It is invoked to explain a wide range of phenomena—by the media, on podcasts, and even by people in everyday conversations. It has been labelled the brain’s chemical of pleasure. We’re supposed to be experiencing ‘dopamine hits’ or ‘rushes’ whenever we engage in activities that lead to gratification. This can be anything from eating chocolate to scrolling through social media feeds. Addictive pursuits from substance abuse through to gaming supposedly flood the brain with dopamine and hijack our actions. Abstaining from pleasure and thereby performing ‘dopamine detoxes’ is therefore necessary to reset dopamine levels. Otherwise, we can develop tolerance to high levels of it, and further stimulation can ultimately drain the brain’s dopamine leaving us flat and unhappy.

There are many books that have been published on these issues. Some exhort us to “master our dopamine” because it is “the molecule of more.” They warn us of the dangers of too much dopamine and provide advice on how to perform a ‘dopamine detox’ or ‘reboot.’ By executing a digital cleanse or breaking bad habits, we can regain ‘dopamine balance.’ Others, on the other hand, describe diets that can trigger the release of dopamine to make us feel happier. Some even offer tips on how to perform ‘dopamine decor’ to bring fun back into our homes. There are books on everything from how to leverage dopamine for dressing well to dressmaking, from how to deploy dopamine fixes for weight loss to rewiring our brain’s dopamine to achieve athletic success.

Dopamine is important for learning which actions are worth being motivated for. But it isn’t the chemical of pleasure.

Overall, the impression that we might be left with is that dopamine is released in the brain whenever something feels good. But modern life overstimulates dopamine through our vices such as junk food, phone apps, video games and drugs. This causes dopamine overload, tolerance, and eventually depletion. As a result, ordinary life stops feeling rewarding. It becomes empty. The solution, therefore, is to reduce stimulation to allow dopamine levels to recover.

The case for this argument is made even more compelling by appealing to neuroscience as the evidence base for these assertions. This narrative has led to the conclusion, for some, that the United States has become a ‘dopamine nation.’ Presumably the same sobriquet might apply to many other countries. But what is dopamine? And what has neuroscience really revealed about what it does?

Dopamine is not a modern chemical. In fact, it is an extremely old and natural one. According to the most conservative estimates, it has been used by biological systems for more than 600 million years. Some of the strongest clues to dopamine’s antiquity come from single-celled organisms that are still present and which use it as a signaling molecule. Dopamine is also found in the earliest multi-cellular organisms with nervous systems and in the brain of the oldest vertebrate that survives to this day—the lamprey.

The lamprey is a jawless, eel-like predator that lives in rivers and has been around for 360 million years. It has a vicious sucker-like mouth lined with teeth and a rasping tongue, both of which have proved invaluable for its evolutionary success. Extensive studies have revealed that the lamprey has nerve cells which use dopamine as a neurotransmitter. Although signals are transmitted along neurons electrically, communication between nerve cells depends on chemical transmission. Tiny bursts of such chemicals allow neurons to signal to each other. Dopamine is one of these chemicals termed neurotransmitters. Many of the neurons that use dopamine reside in the basal ganglia which are nuclei located deep in the lamprey brain. These nuclei are extremely well conserved across different species through evolution, all the way from lampreys to humans.

Dopamine in the lamprey basal ganglia turns out to be crucial for generating movement, and similarly in humans. If dopamine neurons in the basal ganglia degenerate as happens in Parkinson’s disease, movements become harder to initiate and slower once they are commenced. However, dopamine’s key role isn’t in simply executing movements but rather in linking motivation to action. Dopamine is important in the basal ganglia circuits that evaluate whether a particular outcome is worth the effort to make an action. If dopamine is depleted, the effort required to do something may seem formidable and less worthwhile. Hence, fewer movements are made.

But what about dopamine and pleasure? The consensus among neuroscientists is that dopamine does not in fact cause pleasure, as many media stories and books suggest. Instead, dopamine is important for connecting motivation signals to action and for learning about actions that can lead to positive, rewarding outcomes. For example, dopamine is crucial to link motivation about hunger to obtaining food. When we experience hunger, there is an urge—a motivation signal—to find food. We are not going to expire immediately if we don’t find food, but the urge to obtain it inevitably continues to rise, ultimately triggering an action to do so. Dopamine is critical for linking urges—for hunger, thirst, sex, other experiences that can give rise to positive outcomes—to action. But it isn’t the chemical that gives rise to the pleasure itself.

Dopamine does have an important role to play though in addiction to drugs. Most substances of abuse—from cocaine to alcohol—lead to a surge of dopamine in the basal ganglia when these drugs are initially encountered and their stimulating effects are not predictable. This seems to be a common initial response of the brain to drugs that can lead to addiction. However, over repeated exposure to a drug, this dopamine surge effectively becomes blunted, as the effects of taking a drug become predictable.

Then, instead of dopamine neurons firing in response to consuming the drug, they become active when cues or reminders of the exposure to the drug are encountered. This might, for example, occur if walking past the place where the drug was previously consumed. Such reminders can exacerbate drug craving. Dopamine neurons in the basal ganglia thus become most active not when the reward arrives, but when it is predicted based on prior experience.

Dopamine does not enslave us to pleasure, but it can tie us to our expectations from what we have learned through previous experiences.

Over time, this dopamine system is involved in learning which actions are worth repeating—worth making the effort for. This is how we learn which behaviors pay off and how habits—both good and bad—take hold. Thus dopamine is important for learning which actions are worth being motivated for. But it isn’t the chemical of pleasure.

There certainly is no evidence that we experience dopamine ‘hits’ or ‘rushes’ every time we repeatedly engage with social media or use our phone apps. Pleasure can occur without dopamine, and dopamine can be released in the absence of pleasure. Strokes of the basal ganglia can cause highly focal damage which results in dysfunction of the dopamine circuitry. As a result, people can become extremely apathetic, not motivated to do anything, and seemingly inert. For example, they may not be bothered to cook meals, but they can nevertheless gain pleasure from food if someone else cooks it for them. Disruption of dopamine does not take away the hedonic experience of enjoying a meal.

What about dopamine ‘detoxes’? Dopamine is not a toxin. It is a natural chemical used by the brains of a wide range of organisms. Because dopamine is released in tiny bursts when neurons communicate with each other, there is no reservoir of dopamine that builds up in the brain when you scroll, or empties when you abstain. What people usually mean by this term is a break from overstimulating cues—a period of reducing constant novelty, notifications, and temptation. This can be healthy, but crucially not because it drains dopamine from the brain. Abstaining from highly reinforcing digital or other vices can break habits and reduce impulsive behavior such as phone checking. This improvement is cognitive and behavioral, but not a literal dopamine reset.

Dopamine does not enslave us to pleasure, but it can tie us to our expectations from what we have learned through previous experiences. It also turns out to be crucial for motivating actions that lead to positive outcomes. To make matters even more complicated, there is more than one dopaminergic system in human brains. Dopamine is not just present in neurons involved in these processes. Neuroscience has revealed a role for dopamine in circuits involved in short-term memory, decision making and cognitive flexibility—being able to switch to an alternative plan. The truth about dopamine is far more nuanced than current myths suggest.

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Our Brains, Our Selves: What a Neurologist’s Patients Taught Him about the Brain by Masud Husain is available from Canongate.