The ‘Triune Brain’ theory by Neuroscientist Paul MacLean — an evolutionary perspective

Addiction fundamentally alters the brain’s reward and decision-making systems through well-documented neurobiological mechanisms. When substances like drugs (including alcohol and nicotine) are consumed, they trigger massive releases of dopamine in the brain’s reward circuit, particularly in areas like the nucleus accumbens and ventral tegmental area. With repeated exposure, the brain adapts by reducing natural dopamine production and decreasing the number of dopamine receptors, creating tolerance and requiring increasingly larger amounts of the substance to achieve the same effect. This neuroadaptation hijacks the brain’s natural reward system, making everyday activities less rewarding while the addictive substance becomes disproportionately important.

Over time, addiction also impairs the prefrontal cortex, the brain region responsible for executive functions like decision-making, impulse control, and weighing long-term consequences. This creates a neurological double-bind: the midbrain structures driving craving and drug-seeking behaviour become hyperactive, while the prefrontal systems that would normally regulate these impulses become weakened. Chronic substance use also disrupts stress response systems, making individuals more vulnerable to relapse during difficult periods. These changes help explain why addiction is recognised as a chronic brain disease rather than simply a matter of willpower – the neuroplastic changes can persist long after substance use stops, though the brain does have remarkable capacity for recovery with sustained abstinence and appropriate treatment.

The Challenge of Stopping

The challenge of stopping stems from the profound neurobiological changes addiction creates in the brain’s fundamental survival systems. The brain essentially learns to treat the addictive substance as necessary for survival, similar to food or water. When someone tries to quit, they face intense physical withdrawal symptoms as their neurochemistry struggles to return to homeostasis, combined with psychological cravings that can persist for months or years. The damaged prefrontal cortex makes it extremely difficult to override these powerful urges with rational decision-making, while stress, environmental cues, and emotional states can trigger automatic drug-seeking responses that feel almost involuntary. This creates a cycle where attempts to quit often lead to temporary success followed by relapse, which many interpret as personal failure rather than recognising it as part of the neurological reality of the condition.

Addiction appears progressive because tolerance drives escalating use over time, while the brain’s reward system becomes increasingly dysregulated. What begins as recreational use gradually shifts to compulsive use as natural dopamine production diminishes and neural pathways become more deeply entrenched. The condition typically follows a predictable pattern: initial experimentation leads to regular use, then to use despite negative consequences, and finally to compulsive use where the person continues despite severe impairment in major life areas. Additionally, chronic substance use often damages the brain regions responsible for insight and self-awareness, making it harder for individuals to recognise the severity of their condition. The progressive nature is also influenced by external factors – as addiction advances, people often lose social supports, employment, and housing, creating additional stressors that fuel continued use and make recovery more challenging.

Understanding addiction when you’re not “addicted” to alcohol or other drugs

The difficulty in understanding addiction, even among people with their own compulsive behaviors, stems from several key differences in how these conditions manifest and are perceived. While behaviors like sugar consumption, social media use, or shopping can indeed activate similar dopamine pathways, they typically don’t create the same level of neurobiological hijacking that occurs with substances like alcohol, opioids, or stimulants. Addictive drugs often produce dopamine surges 2-10 times greater than natural rewards, creating more profound and lasting changes to brain structure and function. Additionally, many behavioral compulsions allow people to maintain relatively normal functioning in major life areas, whereas substance addiction typically leads to progressive deterioration across multiple domains – relationships, work, health, and legal standing.

The social and cognitive factors also create barriers to understanding. Most people can relate to losing control occasionally – eating too much dessert or spending too much time scrolling their phone – but these experiences usually involve temporary lapses that can be corrected relatively easily through willpower or environmental changes. This creates a false sense of equivalency where people think “I can stop eating cookies when I want to, so why can’t they just stop drinking?” They don’t grasp that addiction involves a qualitatively different level of brain change where the substance has become neurobiologically essential, not just psychologically preferred. There’s also often a moral lens applied to addiction that doesn’t exist for other compulsive behaviours – society tends to view overconsumption of legal, socially acceptable things as personal quirks or minor character flaws, while addiction to illegal substances or excessive alcohol use carries heavy stigma and assumptions about moral failing, making it harder to see as a medical condition requiring treatment rather than simply better self-control.

A Word On Nicotine (Tobacco Products)

Yes, nicotine absolutely does release large amounts of dopamine, making it highly addictive despite being legal and socially accepted in many contexts. Nicotine causes an increase in dopamine levels in the brain’s reward pathways, creating feelings of satisfaction and pleasure.Research shows that nicotine, like opioids and cocaine, can cause dopamine to flood the reward pathway up to 10 times more than natural rewards.

This helps explain why nicotine addiction can be so powerful and difficult to overcome, even though people often view smoking or vaping as less serious than other forms of substance addiction. Repeated activation of dopamine neurons in the ventral tegmental area by nicotine leads not only to reinforcement but also to craving and lack of self-control over intake. The addiction develops through the same basic mechanisms as other substances – as people continue to smoke, the number of nicotine receptors in the brain increases, requiring more of the substance to achieve the same dopamine response.

What makes nicotine particularly insidious is its legal status and social acceptance, which can make people underestimate its addictive potential. The rapid delivery of nicotine to the brain (within 10-20 seconds when smoked) creates an almost immediate reward that strongly reinforces the behaviour. This is why many people who successfully quit other substances still struggle with nicotine, and why nicotine addiction often serves as a gateway that primes the brain’s reward system for addiction to other substances.

To answer that question, I’ll need to explain a part of the brain called the Limbic System.

Within the brain there is a set of structures called the limbic system. There are several important structures within the limbic system: the amygdala, hippocampus, thalamus, hypothalamus, basal ganglia, and cingulate gyrus. The limbic system is among the oldest parts of the brain in evolutionary terms. It’s not just found in humans and other mammals, but also fish, amphibians, and reptiles.

The limbic system is the part of the brain involved in our behavioural and emotional responses, especially when it comes to behaviours we need for survival: feeding, reproduction and caring for our young, and fight or flight responses (https://qbi.uq.edu.au/brain/brain-anatomy/limbic-system).

The limbic system contains the brain’s reward circuit or pathway. The reward circuit links together several brain structures that control and regulate our ability to feel pleasure (or “reward”). The sensation of pleasure or reward motivates us to repeat behaviours. When the reward circuit is activated, each individual neuron (nerve cell) in the circuit relays electrical and chemical signals.

In a healthy world without addictive manufactured drugs, humans survive and thrive when they are rewarded for certain behaviours (cleaning, hard work, sex, eating, achieving goals etc), hence evolution has provided us with this feel-good chemical so that we will repeat pleasurable behaviours.

There is a gap between neurons called the synapse. Neurons communicate with each other by sending an electro-chemical signal from one neuron (pre-synaptic neuron) to the next (post-synaptic neuron). In the reward circuit, neurons release several neurotransmitters (chemical messengers). One of these is called dopamine. Released dopamine molecules travel across the synapse and link up with proteins called dopamine receptors on the surface of the post-synaptic neuron (the receiving nerve cell). When the dopamine binds to the dopamine receptor, it causes proteins attached to the interior part of the post-synaptic neuron to carry the signal onward within the cell. Some dopamine will re-enter the pre-synaptic nerve cell via dopamine transporters, and it can be re-released.

When a reward is encountered, the pre-synaptic nerve cell (neuron) releases a large amount of dopamine in a rapid burst. Dopamine transporters will remove “excessive” amounts of dopamine naturally within the limbic system. Dopamine surges like this help the brain to learn and adapt to a complex social and physical world.

Drugs like methamphetamine (a stimulant drug) are able to “hijack” this process contributing to behaviours which can be considered unnatural or potentially dysfunctional. A range of consequences can follow.

When someone uses methamphetamine, the drug quickly enters the brain, depending on how the drug is administered. Nevertheless, meth or ice is quick acting. Meth blocks the re-entry of dopamine back into the pre-synaptic neuron – which is not what happens naturally. This is also what cocaine does to the brain. However, unlike cocaine, higher doses of meth increase the release of dopamine from the presynaptic neuron leading to a significantly greater amount of dopamine within the synapse. Higher doses of cocaine will not release “more dopamine” from the pre-synaptic neuron like meth does. This is why after about 30 minutes or so, people who use cocaine will need more to maintain the high.

Dopamine gets trapped in the synapse (space between nerve cells) because the meth (like cocaine) prevents “transporters” from removing it back into the cell it came from. The postsynaptic cell is activated to dangerously high levels as it absorbs so much dopamine over a long period of time. The person using meth experiences powerful feelings of euphoria, increased energy, wakefulness, physical activity, and a decreased appetite.

When an unnatural amount of dopamine floods the limbic system like this over a long period of time, without reabsorption, then our brain is not replenished with dopamine, hence people who use meth often (even on a single occasion) may feel unmotivated, depressed, joyless, and/or pointlessness when they stop using. Figuratively speaking, the brain is “empty” or low on dopamine fuel, and it will take time to for dopamine to return to baseline levels and replenish itself. This may motivate the user to seek more methamphetamine to return to “normal”.

Methamphetamine can also cause a variety of cardiovascular problems, including rapid heart rate, irregular heartbeat, and increased blood pressure. Hyperthermia (elevated body temperature) and convulsions may occur with methamphetamine overdose, and if not treated immediately, can result in death (What are the immediate (short-term) effects of methamphetamine misuse? | National Institute on Drug Abuse (NIDA) (nih.gov))

SIGNS OF SUBSTANCE MISUSE OR ADDICTION

• Finding it difficult to meet responsibilities.
• Withdrawing from activities or not enjoying activities that used to provide satisfaction e.g. work, family, hobbies, sports, socialising.
• Taking part in more dangerous or risky behaviours e.g., drink driving, unprotected sex, using dirty needles, criminal behaviour.
• Behaviour changes e.g., stealing, exhibiting violence behaviour toward others.
• Conflict with partner/family/friends, losing friends.
• Experiencing signs of depression, anxiety, paranoia, or psychosis.
• Needing more substance to experience the same effects
• Cravings and urges to use the substance and symptoms of withdrawal when not using the substance.
• Having difficulty reducing or stopping substance use.
• Regretting behaviours while under the influence and continuing to use again.

(Substance abuse, misuse and addiction | Lifeline Australia | 13 11 14)

All human beings experience anger at least occasionally. It’s a natural emotion helping us recognise that we or someone or something we care about has been violated or treated badly. When we feel threatened or our goals are thwarted, anger is a coping mechanism that enables us to act decisively, especially in situations where there is little time to reason things out. It can motivate problem-solving, goal-achievement, and the removing of threats. It serves a protective function and is not always a problem (Lowth, 2018; Stosny, 2020; Zega, 2009).

But anger is a complex emotion, and all too often manifests maladaptively in clients’ lives, when they perceive excessive need for protection, protect the “wrong” things, or use anger to thwart their longer-term best interests. The result is problem anger.

Perhaps because it is so multi-faceted, misperceptions about anger abound, and the question arises: how shall we regard anger? How do we advise the client to think about it? Folk wisdom often would say that the best thing to do is just let it all out, but is it? Clients complain that they cannot control it, that the tendency to be easily angered is inherited, but again, is there evidence for that? Here are common myths people tend to hold about anger, and factual statements following them that you can use to clarify for the client why learning to deal with problem anger is time well spent.

Myth 1: “Anger is inherited.”

This is the client that may try to claim that their father was short-tempered and they have inherited that trait from him, so there is nothing they can do. Such a stance implies an attitude that the expression of anger is a fixed, unalterable set of behaviours. Research shows, however, that expression of anger is learned, so if we have – say, through exposure to aggressive influential others, such as parents – learned to be violent in our expressions, we can also learn healthier, more appropriate, pro-social ways of dealing with it.

Myth 2: “Anger and aggression are the same thing.”

Fact: Nope. Anger is a felt emotional state. Aggression is a behaviour, sometimes carried out in response to anger, but not the same as it. A person can be angry, yet use healthy methods of expression without resorting to violence, threats, or other aggression. Anger does not always lead to aggression. In fact, some experts claim that most daily anger is not followed by aggression. When it does result in aggression the “I3 Model” (pronounced “I cubed”) is deemed responsible. This suggests that aggression emerges as a function of three interacting factors, which all begin with “I”:

Instigation, an event which instils an urge to aggress as a result of, say, being addressed rudely or learning that one’s partner has had an affair (or a relatively “minor” event, such as being cut off in traffic);

Impellance, meaning a force that increases the urge to act in response to an instigating stimulus. These could be strong hormonal releases or a belief system which says that the instigating event should not be tolerated, or even a sociocultural norm which demands that instigating stimuli be responded to immediately and harshly (such as punching back someone who has hit you);

Inhibition, referring to forces that typically work to counter aggression, such as cultural norms, awareness of negative consequences, or perspective-taking or empathy (Kassinove & Tafrate, 2019).

Myth 3: “Other people make me angry.”

Fact: How often in common parlance do we say things like, “He made me so angry!” or “You make me so mad I could kill you!”? Even though we may occasionally speak about people causing emotions other than anger, it is far more frequent to hear such statements in regard to anger. We can choose whether or not we let someone else’s behaviour make us happy, sad, or something else, but we often think and talk about it as if anger is caused directly by others. With the undiscerning listener, an angry person thus gets to use anger as an excuse for unacceptable behaviour. Ultimately, it is not the other person’s behaviour that causes our anger, and in fact, it’s not even their intention, though that may influence our behaviour. Being precise, we must acknowledge that it is our interpretation of their intention, expressed in their behaviour/language, which is causative.

Myth 4: “I shouldn’t hold anger in; it’s better to let it out” (either by venting or catharsis).

Fact: If by “holding it in” someone means that they suppress anger, it’s true; ignoring it won’t make it go away and squashing it down is not a healthy choice. Neither, however, is venting. Blowing up in an aggressive tirade only fuels the fire, reinforcing the problem anger. Ditto the use of pillow-punching or other means of catharsis; this may come as a surprise to therapists trained a few years ago, when catharsis was an anger management technique in good standing. Now researchers have found that, even though we feel better in the moment after hitting something, our brain notices, subtly changing its wiring. Then the next time we are angry it softly whispers, “Hit something; you’ll feel better”. The time after that, the wiring is stronger in the brain towards a hitting catharsis, and the angry-brain-voice speaks a little louder. Continuing in this vein means that eventually, we could decide to hit something more alive than a pillow. Rather than either angry venting or catharsis is the use of skills to manage the angry impulse.

Myth 5: “Anger, aggression, and intimidation help me to earn respect and get what I want.”

Fact: People may be afraid of a bully, but they don’t respect those who cannot control themselves or deal with opposing viewpoints. Communicating respectfully is a far superior way to get (most) people to listen and accommodate one’s needs. While the momentary power that comes with successful intimidation may feel heady in the moment, it does not help build the healthy relationships that most people coming to counselling yearn to have.

Myth 6: Anger affects only a certain category of people.

Fact: Anger is a universal emotion that affects everyone. It does not discriminate against people of any particular age, nationality, race, ethnicity, socioeconomic status, education, or religion. It is tempting for some people in the educated middle classes to believe that anger is more prevalent among the poor, or those who are less educated or lacking in social skills. Reality does not bear this out, although the expressions of anger do vary among different social groups. Remember, anger is just an emotion, one which does not make people “good” or “bad” for having it.

Myth 7: “I can’t help myself. Anger isn’t something you can control.”

We don’t always get to control the situations of our lives, and some of them may trigger our anger. In fact, it’s also agreed by experts that we don’t (in the short-term) control whether we have angry feelings or not; they just come – although there are longer-term ways to work with clients that see them less easily provoked, and therefore less prone to have the experience of anger. What we do have the short-term choice to control is how we express that anger. Continuing in sessions with you (the therapist) for the purpose of learning how to better handle anger means having more choices of response, even in highly provocative situations.

Myth 8: “When I’m angry I will say what I really mean.”

Fact: This is rarely true. Uncontrolled angry expressions are more about gaining control of or hurting others, not saying what a person’s deepest truth is. 

Myth 9: “By not saying what I’m thinking in the moment, I’m being dishonest and will be even angrier later.”

Fact: There is a strong pull to “speak our mind” when angry. But it is at this time that a person’s judgment is most severely flawed. To speak from anger is to allow the impulsive part of the brain to overrule the rational part. Better for relationships, career, and pretty much everything else to wait until that reasoning part can regain control.

Myth 10: “Men are angrier than women.”

Fact: The sexes experience the same amount of anger, says research; they just express it differently. Men often use aggressive tactics and expressions, whereas women (often constrained culturally) more frequently choose indirect means of expression, such as found in passive-aggressive tactics. This could mean getting back at someone by talking negatively about them or cutting them out of their lives (categories adapted from: Therapist Aid LLC, 2016; Segal & Smith, 2018; Morin, 2015; Morrow, n.d.; Better Relationships, 2021; Gallagher, 2001).

Thought for reflection

Anger has many facets to it, and we have introduced some information here that may seem either startling or counterintuitive. As you think back over the myths we just debunked, which aspect has surprised you the most? Do you have any sense of why that might be? One woman, for example, was very surprised to hear that “men are angrier than women” was only considered a myth; it turned out that in her family, women “never got angry” (we hypothesise that perhaps they were socialised to not show anger), and the men got angry all the time (perhaps more allowed in that woman’s family/culture). In what ways, if at all, might your views about anger have shaped how you behave? How you respond to others? 

And here’s the ultimate question if you share this material with a client: what are their responses to the above questions? How might hearing these myths help them seek more adaptive ways to deal with problem anger? 

The upcoming Mental Health Academy course, “Helping Clients Deal with Problem Anger” draws from numerous therapies and neuroscience to help clinicians and clients collaboratively create a program to address each client’s unique challenges with this universal human emotion.

References:

1. Better Relationships. (2021). Common myths about anger. Anglicare Southern Queensland. Retrieved on 13 April, 2021, from: Website.
2. Gallagher, E. (2001). Anger. eddiegallagher.com.au. Retrieved on 13 April, 2021, from: Website.
3. Kassinove, H., & Tafrate, R.C. (2019). The practitioner’s guide to anger management: Customizable interventions, treatments, and tools for clients with problem anger. Oakland, CA: New Harbinger Publications, Inc. 
4. Lowth, M. (2018). Anger management. Patient. Retrieved on 7 April, 2021, from: Website.
5. Morin, A. (2015). 7 myths about anger and why they’re wrong. Psychology Today. Retrieved on 13 April, 2021, from: Website.
6. Morrow, A. (n.d.). Anger myths. Stress and Anger Management Institute. Retrieved on 13 April, 2021, from: Website.
7. Segal, J., & Smith, M. (2018). Anger management: Tips and techniques for getting anger under control. Helpguide.org. Retrieved on 9 April, 2021, from: Website.    
8. Stosny, S. (2020). Beyond anger management. Psychology Today. Retrieved on 9 April, 2021, from: Website.
9. Therapist Aid, LLC. (2016). Anger warning signs. Therapist Aid LLC. Retrieved on 7 April, 2021, from: Website.
10. Zega, K. (2009). Holistic Psychotherapy (159). Retrieved on 7 April, 2021, from: Website.