• The OAD Clinic

The Brain and Addiction - Part III

Updated: Jul 16

Do we have three brains?


Now we know that in the early century XX neuroscientists were able to understand the roots of some of Jon’s symptoms, mostly those related to very basic primitive behaviours, hiding deep inside the human brain because they were one of the first brain structures to develop during the evolution process. They first appeared in reptiles and other species with relative simpler brain structures. The so called Reptile brain.


Those structures can explain basic human instinctive short lasting reactions, with no elaborate emotions and feelings involved, nor long lasting memories of it.

The lizard inside us all.


As decades went by, extraordinary events occurred. Some 140 million people were killed within a 30 year period (1914-1945). WWI resulted in 40 million deaths, WWII in 75 million deaths, and a further 20 million also died as direct or indirect consequence of the Russian Revolution. And we say Coronavirus is lethal… What about humans?


Well, that’s exactly what many people wondered at the time, and that was what prompted, along with new scientific advances in neurobiology, neurology, neurosurgery, psychiatry and psychology, a new age of research and discoveries in human brain and human mind.


No doubt we are intelligent, but why do we behave in such aggressive ways? How can humans be capable of such cruelty? Not even the Reptilian part of our brain can explain such destructiveness, unheard of in the animal kingdom, supposedly inferior to humans…

But that was exactly the nature of the paradox. We have a reptilian brain but also human intelligence as well. That combination of intelligence and animal instinct makes us dangerous.


We were able to create increasingly elaborate means of destruction, driven by the basic aggressive instincts deep in our brains. When the more developed parts of our brain work together with the most primitive ones, intelligence and basic aggressive instincts get their way. That’s how during WWI for the first time industrial revolution engineering was applied to war waging, to create killing machines.


Savage animals are very capable of killing, but the concept of torture and vengeance upon their victims does not seem to exist. And that applies not just to sadistic behaviours, but masochistic as well.


It is not just the stimulation of deep structures in our brains by drugs that induce self-destructive behaviours, but the damage to our most evolved parts (pre frontal cortex) as well. That could explain the loss of humanity fuelled by hard drugs. The forebrain turns servant to the Reptilian Brain.


During those WWI years Freud's ideas and theories flourished and became the new trend in psychology. The concepts of unconscious primitive drives (psychological) / instincts (biological) taking over the human psyche became popular because humans have proven to be a lot less rational than they thought they were.


In the early century XX Freud's and Jung's psychoanalytic theories led the way to understanding human behaviour and treating its “deviations” with psychotherapy.

Their theories and ideas were supported by little or almost non-existent empirical evidence, although they did provide a rational framework for professional psychological treatment.


Something similar happened with Psychiatry, where pragmatic interventions using a few medications and medical procedures were utilized, sometimes resulting in very negative outcomes. Neurobiological sciences continued developing at a steady but slow pace in relation to the acute need for evidence based treatments of mental disorders.

By the mid-50s there was a much better understanding of brain development and how it works, and by 1964 Paul MacLean, an American clinician and neuroscientist, proposed the evolutionary Triune Brain theory. Communicators such as Paul Koestler and Carl Sagan made his theory more understandable to the public, captivating their imaginations. MacLean’s Triune Brain (TB) resembles a neuroanatomical correlate to Freud’s tripartite view of the mind: id, ego and superego.


We know today that the TB theory has many flaws and many recent discoveries in neuroscience contradict the model, however when it was launched some 60 years ago it was widely accepted by scientists and clinicians. MacLean's theory provided a relative simple integration of central nervous system phylogenetic evolution, neuro-embryologic development, and mature brain structures with different levels of function.

Now we know it is not that simple, but the TB model was appealing (it still is) and not too difficult to understand.


The TB consists of three independent, conscious, sequential structures resulting from evolution. These brain structures develop like a Russian doll. The most internal parts are the most ancient ones, first to appear in amphibia. The intermediate structures (midbrain) appeared for the first time in vertebrates, and the outer dorsal ones in superior mammals.

Following MacLean's ideas, we could say that in some way, we have three brains that have evolved over eons to become one.


What makes human brain different from the rest of superior mammals, is a much more developed pre-frontal brain cortex, bigger in size and neural complexity when compared to primates. It is very important to understand the brain structures, how they work and how they interact, if we are to provide a rational evidence based treatment for mental health disorders, including addictions.


Dr Oscar D'Agnone, MD, MRCPsych.

Medical Director

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