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

Abstract

Addiction is a complex, multifaceted phenomenon that has been described variously as a disease, disorder, syndrome, obsessive-compulsive behaviour, learned behaviour, or spiritual malady. Modern scientific understanding emphasises addiction as a chronic brain disorder shaped by neurobiological changes, learning, and social context. This article examines each conceptualisation and presents an integrated definition that aligns with current neuroscience, psychological, and public health evidence.

Conceptualising Addiction: Labels and Their Accuracy

No single label fully captures addiction’s complexity; each highlights certain truths while overlooking others.

Disease

From a medical perspective, disease is the closest match. Addiction involves persistent neurobiological changes in reward, stress, and self-control circuits, increases relapse risk over years, and shows substantial genetic vulnerability (~50–60%) (NIDA, 2018; Heilig et al., 2021). Treatments improve outcomes but rarely “cure” the condition. This framing is used by the American Society of Addiction Medicine (ASAM), NIDA, WHO ICD-11, and DSM-5-TR (as “Substance Use Disorder”) (NIDA, 2018).

Disorder

Disorder is also scientifically accurate and slightly less medicalised. DSM-5’s “Substance Use Disorder” captures behavioural, psychological, and biological criteria and recognises functioning and harm rather than framing addiction strictly as a lifelong disease (Heather, n.d.; Heilig et al., 2021).

Syndrome

Addiction may be described as a syndrome because it is a cluster of symptoms with behavioural and physiological manifestations, without a single causative factor. However, the term is too generic for practical use outside clinical texts (Blithikioti et al., 2025).

Obsessive and Compulsive Learned Behaviour

Addiction involves learning, habit formation, and compulsion through reinforcement of rewarding behaviours (Hyman, 2005; Hausotter, 2013). Yet describing it solely as learned behaviour ignores genetic predisposition, neuroadaptation, withdrawal, and social factors.

Spiritual Malady

Some mutual-aid traditions characterise addiction as a spiritual malady. While this may be meaningful for individuals, it is not scientifically explanatory: addiction can be adequately explained via biological, psychological, and social mechanisms (Lewis, 2017).

Modern Integrative Definition

The most accurate contemporary description of addiction is:
“A chronic, relapsing disorder of brain circuits involved in reward, stress, and self-control, shaped by learning, environment, and social context”.

This definition encompasses:

• Disease/disorder: medical accuracy
• Learned behaviour and compulsion: neuroscience and behavioural accuracy
• Social determinants: public health relevance
• Flexibility for personal or spiritual interpretations

In short, addiction is best understood as a bio-psycho-social condition that is treatable and sometimes reversible, rather than a deterministic, lifelong curse.

Neurobiology: Why Addiction Is Considered a Brain Disorder

Repeated substance use alters structural and functional brain circuits involved in reward, stress, motivation, memory, and self-control (Nwonu et al., 2022; NIDA, 2018). These changes can persist long after use stops, explaining why addiction is more than a matter of “bad habits” or weak will (NIDA, 2025).

Chronicity and Relapse

Addiction is often chronic and relapsing. Even after long periods of abstinence, cues and stressors can trigger relapse (Meurk et al., 2014; SAMHSA, 2023). Key regions implicated include the basal ganglia (habit formation), extended amygdala (stress), and prefrontal cortex (decision-making) (Kirby et al., 2024). Nevertheless, many individuals achieve stable remission, highlighting heterogeneity in clinical outcomes (Heilig et al., 2021).

Learning, Memory, and Habit Formation

Addiction exploits neural mechanisms of learning and memory: rewarding behaviours are repeated and consolidated into habits, with cues triggering compulsive responses even when the substance’s reward diminishes (Hausotter, 2013; Lewis, 2017). This intertwines biological disorder and learned behaviour.

Critiques and Limitations

Some scientists caution that framing addiction strictly as a brain disease is simplistic:

• Brain changes may resemble those from other motivated behaviours (Lewis, 2017).
• Many recover without formal treatment (Heilig et al., 2021).
• Social, environmental, and psychological factors are crucial to understanding addiction (Blithikioti et al., 2025).

Thus, while the disease model is powerful, it does not fully represent addiction’s heterogeneity or socio-psychological dimensions.

Implications for Treatment

Addiction is treatable, not simply curable. Interventions combining pharmacological and behavioural approaches, alongside social support, can foster long-term recovery (Liu & Li, 2018; Heilig et al., 2021). Like other chronic conditions, management — rather than elimination — is often the realistic goal (NIDA, 2018). Neural circuits can gradually readjust, particularly when environmental and personal factors support recovery.

Conclusion

Addiction is a learned, compulsive brain disorder with chronic potential, shaped by neurobiological, psychological, social, and environmental factors. Recognising addiction as both a disorder and a behavioural learning condition avoids extremes: it is neither an unchangeable fate nor merely a moral failing. This integrated perspective supports nuanced understanding, compassionate care, and effective treatment strategies.

References

Blithikioti, C., Fried, E. I., Albanese, E., Field, M., & Cristea, I. A. (2025). Reevaluating the brain disease model of addiction. The Lancet Psychiatry, 12(6), 469–474. https://doi.org/10.1016/S2215-0366(25)00060-4

Hausotter, W. (2013). Neuroscience and understanding addiction. Addiction Technology Transfer Center (ATTC) Network. https://attcnetwork.org/neuroscience-and-understanding-addiction

Heather, N. (n.d.). What’s wrong with the brain disease model of addiction (BDMA)? Addiction Theory Network. https://addictiontheorynetwork.org/brain-disease-model-of-addiction

Heilig, M., MacKillop, J., Martinez, D., Rehm, J., Leggio, L., & Vanderschuren, L. J. M. J. (2021). Addiction as a brain disease revised: Why it still matters, and the need for consilience. Neuropsychopharmacology, 46(10), 1715–1723. https://doi.org/10.1038/s41386-020-00950-y

Hyman, S. E. (2005). Addiction: A disease of learning and memory. The American Journal of Psychiatry, 162(8), 1414–1422. https://doi.org/10.1176/appi.ajp.162.8.1414

Kirby, E. D., Glenn, M. J., Sandstrom, N. J., & Williams, C. L. (2024). Neurobiology of addiction (Section 14.5). In Introduction to Behavioral Neuroscience. OpenStax. https://socialsci.libretexts.org/…/14.05:_Neurobiology_of_Addiction

Leshner, A. I. (1997). Addiction is a brain disease, and it matters. Science, 278(5335), 45–47. https://doi.org/10.1126/science.278.5335.45

Lewis, M. (2017). Addiction and the brain: Development, not disease. Neuroethics, 10(1), 7–18. https://doi.org/10.1007/s12152-016-9293-4

Liu, J. F., & Li, J. X. (2018). Drug addiction: A curable mental disorder? Acta Pharmacologica Sinica, 39(12), 1823–1829. https://doi.org/10.1038/s41401-018-0180-x

Meurk, C., Carter, A., Partridge, B., Lucke, J., & Hall, W. (2014). How is acceptance of the brain disease model of addiction related to Australians’ attitudes towards addicted individuals and treatments for addiction? BMC Psychiatry, 14, 373. https://doi.org/10.1186/s12888-014-0373-x

National Institute on Drug Abuse. (2018). Drugs, brains, and behavior: The science of addiction (Rev. ed.). https://irp.nida.nih.gov/…/NIDA_DrugsBrainsAddiction

Nwonu, C. N. S., Nwonu, P. C., & Ude, R. A. (2022). Neurobiological underpinnings in drug addiction. West African Journal of Medicine, 39(6), 874–884. https://pubmed.ncbi.nlm.nih.gov/36063103

Substance Abuse and Mental Health Services Administration. (2023). What is substance use disorder? U.S. Department of Health and Human Services. https://www.samhsa.gov/substance-use/what-is-sud

What is meant by self-harm?

Self-harm is any behaviour that involves the deliberate causing of pain or injury to oneself without the intention to end your life. Self-harm can include behaviours such as cutting, burning or hitting oneself, binge-eating or starvation, or repeatedly putting oneself in dangerous situations. It can also involve abuse of drugs or alcohol, including overdosing on prescription medications. Self-harm is usually a response to distress, whether it be from mental illness, trauma, or psychological pain. Some people find that the physical pain of self-harm helps provide temporary relief from emotional pain (extract from Self harm (lifeline.org.au)).

People who engage in self-harm will profess that they have no intention of dying and that their self-harming behaviour is a coping strategy, however, there are incidents of accidental suicide. The act of self-harm can develop into an obsessive-compulsion experience which can be very difficult to stop, like addiction, without outside intervention. This can result in feelings of hopelessness and possible suicidal thinking. Like building a tolerance to a drug, when self-injury does not relieve the tension or help control negative thoughts and feelings, the person may injure themselves more severely or may start to believe they can no longer control their pain and may consider suicide.

The following extract by Tracy Alderman Ph.D explains the physiological response to physical pain:

“Physiologically, endorphins are released when we are injured or stressed. Endorphins are neurotransmitters that act similarly to morphine and reduce the amount of pain we experience when we are hurt. Joggers often report experiencing a “runners high” when reaching a physically stressful period. This “high” is the physiological reaction to the release of endorphins – the masking of pain by a substance that mimics morphine. When people self-injure, the same process takes place. Endorphins are released which limit or block the amount of physical pain that’s experienced. Sometimes people who intentionally hurt themselves will even say that they felt a “rush” or “high” from the act. Given the role of endorphins, this makes perfect sense” (Oct 22, 2009).

Please click on the link for the full article Myths and Misconceptions of Self-Injury: Part II | Psychology Today Australia

The first step is to distinguish between self-harming and suicidal behaviour by paying attention to a person’s underlying motivation. When working with self-harming behaviour it is important to remember that this behaviour serves a purpose. In collaboration with the client, try to identify what problem self-harm solves for the client. For example, from the client’s perspective:

• To make me feel real (counteracts dissociation)
• To punish me (temporarily lessens guilt or shame)
• To stop me from feeling (when strong feelings are too dangerous)
• To mark the body (to show externally the internal scars)
• To let something bad out (symbolic way to try to get rid of shame, pain, etc.)
• To remember
• To keep from hurting someone else (to control my behaviour and my anger)
• To communicate (to let someone know how bad the pain is)
• To express anger indirectly (to punish someone without getting them angry at me)
• To reclaim control of the body (this time I’m in charge)
• To feel better

Tips for helping yourself in the moment
It can be hard for people who self-harm to stop it by themselves. That’s why it’s important to get further help if needed; however, the ideas below may be helpful to start relieving some distress:

• Intense exercise for 30 seconds, 30 second break, repeat, up to 15 minutes – Exercising intensely will help your body mitigate unpleasant energy that can sometimes be stored from strong emotions. Transfer this energy by running, walking at a fast pace, doing jumping jacks, etc. Exercise naturally releases endorphins which will help combat any negative emotions like anger, anxiety, or sadness.
• Delay — put off self-harming behaviours until you have spoken to someone.
• Distract — do some exercise, go for a walk, play a game, do something kind for yourself, play loud music or use positive coping strategies.
• Deep breathing — or other relaxation methods.
• Cool your body temperature – Cooler temperatures decrease your heart rate (which is usually faster when we are emotionally overwhelmed). You can either splash your face with cold water, take a cold (but not too cold) shower, or if the weather outside is chilly you can go outside for a walk. Another idea is to take an ice cube and hold it in your hand or rub your face with it.
• Listen to loud music
• Call someone you trust or one of the services available like LifeLine 13 11 14, MensLine Australia 1300 78 99 78 and BeyondBlue 1300 22 4636 [see below].
• You could write an email to yourself to express your emotions, or journal your feelings, if that’s something that might be effective for you.
• Watch humorous Youtube clips

New, healthier coping strategies may not be as effective as the one you’re trying to replace so it may take practice. Bring lots of compassion to yourself, okay.

You may find that some of these strategies work in some situations but not others, or you may find that you need to use a combination of these. It’s important to find what works for you. Also, remember that these are not long-term solutions to self-harm but rather, useful short-term alternatives for relieving distress.

If you’ve ever found yourself thinking “Part of me wants to change… but part of me’s not sure”, you’re not alone. That back-and-forth, weighing things up—“Should I? Shouldn’t I?”—is a normal part of how people process big (and small) decisions. In counselling, this is called ambivalence, and rather than seeing it as a barrier, Motivational Interviewing (MI) treats it as a starting point for meaningful conversations.

What Is Motivational Interviewing?

Motivational Interviewing is a counselling approach that helps people explore their own reasons for change, without pressure or judgment. It’s a respectful, supportive way of helping you work through the push-pull that often comes with making decisions. You’re in the driver’s seat—we’re just here to help you navigate.

You might hear MI described in different ways:

In simple terms:
“MI is a collaborative conversation style that helps strengthen your own motivation and commitment to change.”

In practice:
“MI is about helping you make sense of mixed feelings and explore what’s right for you—based on your values, your goals, and your life.”

MI isn’t about telling you what to do. It’s about listening deeply, asking thoughtful questions, and helping you make sense of where you’re at—and where you might want to go.

Why It’s Not Just a Quick Fix

While MI can be used in short sessions, the research shows it works best when there’s time to really explore your thinking. In studies where people had just one 15-minute session, the outcomes were decent. But when they had more time—say, several sessions of an hour—the results were much stronger. That’s probably because real change often takes time, reflection, and a bit of back-and-forth.

MI originally started in the health world—helping people reduce alcohol use, manage weight, or improve their health. More recently, it’s been used to address things like vaccine hesitancy. But MI isn’t just for health issues. It can also help with things like relationship struggles, career decisions, or anything where you might feel stuck or unsure.

Ambivalence Is Normal

Let’s say you’re thinking about quitting smoking, leaving a relationship, or starting something new. You might feel torn—part of you is ready, and another part isn’t. That’s ambivalence.

MI offers tools to help with this, including something called the Decisional Balance, which simply helps you look at both sides: What are the good things about staying the same? What are the reasons you might want to change?

But here’s the thing—MI isn’t about pushing you toward a particular outcome. If you’re trying to make a decision where there’s no obvious “right” answer—like whether to stay in a relationship—the counsellor stays neutral. They don’t steer you in one direction. Instead, they help you explore what matters to you.

Talking Your Way Toward Change

One of the interesting things about MI is how it pays attention to the language you use when you talk about change.

Some of the things people say when they’re starting to think about change include:

• “I probably should cut down…”
• “I’d like to feel better about this…”
• “I don’t know if I can keep doing this…”

These kinds of statements are called change talk—and they’re actually signs that something inside you is shifting. MI aims to gently encourage and grow this kind of talk, because research shows that the more someone talks about change, the more likely they are to act on it.

There’s also sustain talk, which sounds like:

• “I don’t smoke that much…”
• “I know I should, but it helps me relax.”
• “Now’s not really the right time.”

Both are normal. In MI, there’s no need to rush. Instead, the focus is on listening to both sides of you—and helping you get clearer about what you want to do next.

Getting Skilled Support

Like any professional approach, MI works best when the counsellor is trained and skilled in using it. Some practitioners have their sessions reviewed (with consent) by independent experts to make sure the spirit and skills of MI are being used well.

If you ever hear a practitioner say they “do MI”, you can ask what that looks like. The most effective use of MI goes beyond just asking open-ended questions or offering summaries—it’s about how your counsellor supports you in finding your own reasons for change.

What a Session Might Involve

Motivational Interviewing tends to follow a flexible process with four key parts:

1. Engaging – Building trust and understanding
2. Focusing – Exploring what matters most to you
3. Evoking – Drawing out your own reasons for change
4. Planning – When you’re ready, looking at possible next steps

You don’t have to go through these in a straight line. Some days you might focus on one step, then circle back to another later. It’s all guided by you—your pace, your readiness, your goals.

In Summary

If you’re feeling uncertain about making a change—or you’ve been thinking about it for a while but haven’t quite landed on what to do—Motivational Interviewing could be a really helpful way to explore things.

It’s not about being told what to do, and it’s not about “fixing” you. It’s a respectful, evidence-based approach that helps people work through their own ambivalence, connect with what matters to them, and move toward change when they’re ready.

Change doesn’t have to be instant. And it doesn’t have to be perfect. But it can start with a conversation.