How We Are Wired For Addiction
For many people, their addictions govern a surprising proportion of their lives and determine and control many of their day-to-day behaviours. Sometimes this may be an addiction to something as seemingly harmless as having a coffee and toast at breakfast every day or it may be to using a substance that is patently likely to result in harm such as smoking or using recreational drugs. Many use a variety of substances, consciously or unconsciously, to self-medicate and anaesthetise the pain that they feel.
In fact, addiction is probably a huge and largely unrecognised factor underscoring a wide variety of health problems including liver and lung diseases, obesity, type II diabetes and cardiovascular disease. This article examines some of the mechanisms by which we can fall prey to addiction. And since all addictive substances exert their effects upon the brain, we shall start there.
The brain
The brain is a fantastically complex communications network consisting of billions of nerve cells known as neurons. Neurons in the peripheral nervous system transmit messages to and fro between the body and the central nervous system and networks within the brain and spinal column route signals within the body of the central nervous system. These networks of neurons control everything that we feel, think, and do.
Neurons
Messages are transmitted within this network from one neuron to another across ‘junctions’ known as synapses. When the sending neuron is stimulated it causes chemical messengers known as neurotransmitters to be released from little sacs (vesicles) in its expanded terminal end. These then pass across the space (synaptic cleft) between the neurons and bind to specific receptors on the surface of the receiving neuron.
These neurotransmitters act like keys in a lock and activate various processes within the receiving neuron such as turning different genes on and this is known as transduction. Once the neurotransmitter has passed its chemical message to the receiving neuron, it is transported back into the sending neuron where it is re-stored. The substances responsible for this are known as transporters and the mechanism is known as re-uptake.
Up-regulation and down-regulation
The body seeks to maintain the steady state known as homeostasis at all times, and so if a neuron is over-stimulated by neurotransmitters it will either reduce the sensitivity of the available receptors and/or reduce their number dynamically. These processes are known as desensitisation and down-regulation respectively. If the neuron is receiving insufficient stimulation, then the receptors will become more sensitive and their number increased in processes known as sensitisation and up-regulation. All these processes are very dynamic and can occur within minutes and even after a single event of the neuron being over- or under-stimulated. The processes of desensitisation and down-regulation also result in developing tolerance, where more of a substance is required over time to achieve the same response.
Dopamine and addiction
The part of the brain thought to be particularly involved in the development of addiction and reward is the substantia nigra in the midbrain which is Latin for ‘black substance’. It was given this name because of its dark appearance due to the high levels of melanin present in this region. The neurons in this area produce the neurotransmitter, dopamine, which is chemically very similar to adrenaline (epinephrine) and plays a crucial role in our mental, emotional and physical health and our ability to experience pleasure and pain. In Parkinson's disease, the neurons in this region are destroyed leading to the profound rigor associated with this disorder.
How mood-altering drugs work
All drugs - be they recreational or pharmacological - that alter mood exert their effects upon the process of synaptic transmission between neurons either directly or indirectly. This is the basis of addiction. Marijuana and heroin, for instance, have direct effects because their chemical structure mimics that of natural endogenous neurotransmitters. Whereas, cocaine and amphetamines, have indirect actions by binding the proteins responsible for transporting dopamine so that the receiving neuron is heavily stimulated and it is this that causes the prolonged feelings of pleasure and excitement. Pharmacological drugs such as the selective serotonin reuptake inhibitor (SSRI), Prozac, act in a similar way on the neurons that produce the neurotransmitter, serotonin, causing relief of depression.
Any drug that alters mood can cause addiction by exerting an effect upon one or all of the following regions of the brain:
The brain stem which links the brain and spinal cord and regulates all automatic functions such as breathing, circulation and digestion in addition to processing incoming information from the body and controlling the movement of muscles.
The limbic system which is a collection of structures that control our emotional responses. All behaviours necessary for survival such as eating and drinking are rewarded by feelings of pleasure generated here which motivate us to repeat the behaviour in a reward circuit.
The cerebral cortex or higher, thinking centre which is responsible for thinking, planning, solving problems and making decisions.
The process of addiction
All substances that can act upon receptors as described cause initial feelings of relief of tension and mood changes. With continued use, there follows an onset phase where the user becomes preoccupied with the addictive substance and comes to rely upon using the substance to control their moods and to feel ‘normal’. This leads progressively into dependence with excessive use, loss of control, deterioration in self-image and possible self-destructive behaviour. Many who break a cycle of addiction to a particular substance, ultimately end up transferring their addictive behaviour to another substance so that someone who has combated alcoholism, for instance, may subsequently turn to food to control their moods.
Leptin is a relatively recently discovered fat-derived hormone that governs appetite, metabolism and energy production. It is thought to be as important as insulin and through its actions upon the dopamine-releasing neurons adversely affects the reward circuit in the limbic system causing the development of addiction. Dysfunction of this pathway is thought to be a primary cause of weight gain and overeating and is also thought to be intimately involved in the processes of development of chronic illness.
The body/mind connection
According to the work of Dr Candace Pert the neurotransmitters form a link between the body and the mind with emotions too producing peptides that communicate with the body. This means that the same processes involved in developing drug addiction can also apply to endogenously produced substances that lead us to become addicted to our habitual emotions. These patterns of addiction are thought to be determined by the time we are 20 years of age. Ultimately, unresolved trauma is thought to be the underlying cause of both addiction and relapse.
The good news, however, is that the brain is incredibly responsive and plastic and if you can consciously choose to break both the addiction and the habitual emotions you can liberate yourself, recover and create not only a new vision for yourself, but also a new brain.
For many people, their addictions govern a surprising proportion of their lives and determine and control many of their day-to-day behaviours. Sometimes this may be an addiction to something as seemingly harmless as having a coffee and toast at breakfast every day or it may be to using a substance that is patently likely to result in harm such as smoking or using recreational drugs. Many use a variety of substances, consciously or unconsciously, to self-medicate and anaesthetise the pain that they feel.
In fact, addiction is probably a huge and largely unrecognised factor underscoring a wide variety of health problems including liver and lung diseases, obesity, type II diabetes and cardiovascular disease. This article examines some of the mechanisms by which we can fall prey to addiction. And since all addictive substances exert their effects upon the brain, we shall start there.
The brain and neurons
The brain is a fantastically complex communications network consisting of billions of nerve cells known as neurons. Neurons in the peripheral nervous system transmit messages to and fro between the body and the central nervous system and networks within the brain and spinal column route signals within the body of the central nervous system. These networks of neurons control everything that we feel, think, and do.
Neurons and addiction
Messages are transmitted within this network from one neuron to another across ‘junctions’ known as synapses. When the sending neuron is stimulated it causes chemical messengers known as neurotransmitters to be released from little sacs (vesicles) in its expanded terminal end. These then pass across the space (synaptic cleft) between the neurons and bind to specific receptors on the surface of the receiving neuron.
These neurotransmitters act like keys in a lock and activate various processes within the receiving neuron such as turning different genes on and this is known as transduction. Once the neurotransmitter has passed its chemical message to the receiving neuron, it is transported back into the sending neuron where it is re-stored. The substances responsible for this are known as transporters and the mechanism is known as re-uptake.
The processes of up-regulation and down-regulation
The body seeks to maintain the steady state known as homeostasis at all times, and so if a neuron is over-stimulated by neurotransmitters it will either reduce the sensitivity of the available receptors and/or reduce their number dynamically. These processes are known as desensitisation and down-regulation respectively. If the neuron is receiving insufficient stimulation, then the receptors will become more sensitive and their number increased in processes known as sensitisation and up-regulation. All these processes are very dynamic and can occur within minutes and even after a single event of the neuron being over- or under-stimulated. The processes of desensitisation and down-regulation also result in developing tolerance, where more of a substance is required over time to achieve the same response.
Dopamine and addiction
The part of the brain thought to be particularly involved in the development of addiction and reward is the substantia nigra in the midbrain which is Latin for ‘black substance’. It was given this name because of its dark appearance due to the high levels of melanin present in this region. The neurons in this area produce the neurotransmitter, dopamine, which is chemically very similar to adrenaline (epinephrine) and plays a crucial role in our mental, emotional and physical health and our ability to experience pleasure and pain. In Parkinson's disease, the neurons in this region are destroyed leading to the profound rigor associated with this disorder.
How mood-altering drugs work
All drugs - be they recreational or pharmacological - that alter mood exert their effects upon the process of synaptic transmission between neurons either directly or indirectly. This is the basis of addiction. Marijuana and heroin, for instance, have direct effects because their chemical structure mimics that of natural endogenous neurotransmitters. Whereas, cocaine and amphetamines, have indirect actions by binding the proteins responsible for transporting dopamine so that the receiving neuron is heavily stimulated and it is this that causes the prolonged feelings of pleasure and excitement. Pharmacological drugs such as the selective serotonin reuptake inhibitor (SSRI), Prozac, act in a similar way on the neurons that produce the neurotransmitter, serotonin, causing relief of depression.
Any drug that alters mood can cause addiction by exerting an effect upon one or all of the following regions of the brain:
-
The brain stem which links the brain and spinal cord and regulates all automatic functions such as breathing, circulation and digestion in addition to processing incoming information from the body and controlling the movement of muscles.
-
The limbic system which is a collection of structures that control our emotional responses. All behaviours necessary for survival such as eating and drinking are rewarded by feelings of pleasure generated here which motivate us to repeat the behaviour in a reward circuit.
-
The cerebral cortex or higher, thinking centre which is responsible for thinking, planning, solving problems and making decisions.
The development of an addiction
All substances that can act upon receptors as described cause initial feelings of relief of tension and mood changes. With continued use, there follows an onset phase where the user becomes preoccupied with the addictive substance and comes to rely upon using the substance to control their moods and to feel ‘normal’. This leads progressively into dependence with excessive use, loss of control, deterioration in self-image and possible self-destructive behaviour. Many who break a cycle of addiction to a particular substance, ultimately end up transferring their addictive behaviour to another substance so that someone who has combated alcoholism, for instance, may subsequently turn to food to control their moods.
Leptin and addiction
Leptin is a relatively recently discovered fat-derived hormone that governs appetite, metabolism and energy production. It is thought to be as important as insulin and through its actions upon the dopamine-releasing neurons adversely affects the reward circuit in the limbic system causing the development of addiction. Dysfunction of this pathway is thought to be a primary cause of weight gain and overeating and is also thought to be intimately involved in the processes of development of chronic illness.
The body/mind connection
According to the work of Dr Candace Pert the neurotransmitters form a link between the body and the mind with emotions too producing peptides that communicate with the body. This means that the same processes involved in developing drug addiction can also apply to endogenously produced substances that lead us to become addicted to our habitual emotions. These patterns of addiction are thought to be determined by the time we are 20 years of age. Ultimately, unresolved trauma is thought to be the underlying cause of both addiction and relapse.
The good news, however, is that the brain is incredibly responsive and plastic and if you can consciously choose to break both the addiction and the habitual emotions you can liberate yourself, recover and create not only a new vision for yourself, but also a new brain.
Further resources
For books on related topics see the Emotional and Spiritual Health section of Recommended Reading. For a comprehensive approach to detoxification and diet refer to The Natural Recovery Plan book
"Alison's journey to good health should be an inspiration to all. En route she has to oust what must be one of the most complex and least understood diseases of the 21st century."
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