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Neurobiology Of Addiction

What Is Addiction?

Addiction is the condition of being addicted to a substance or an activity. Addiction is represented by a traumatic dysregulation in the motivational circuit which is caused by a combination of habit formation, inflated incentive salience, excessive stress, and reward deficits.

Drugs have habit-forming actions. Chemical trigger zones that initiate habit-forming actions of individual drugs reveal that drugs like heroin, cocaine, nicotine, alcohol, and cannabis activate reward circuitry in the brain.

Addiction is induced by drugs, in the form of neural plasticity. It is also known as substance dependence and is characterized by the compulsion to take drugs, and the inability to control self by limiting intake. A negative emotional state including dysphoria, irritability, and anxiety occurs when access to the substance is prevented.

Addiction involves various symptoms that include tolerance, withdrawal symptoms, persistent desire or unsuccessful effort to cut down despite interference with social or interpersonal functions, failure to fulfill major role obligations, and continued use despite physical, and psychological problems caused.

The Biology Of Addiction

As the individual consumes a substance, it creates a neurotransmitter imbalance in the Brain. There is a surge in Dopamine in the basal ganglia region, which controls our reward system of the body and how we process it. With constant substance consumption, the brain adapts to the increased hormone. Then the body becomes tolerant to the dosage and hence requires more to get the same pleasure and this is how people become addicted, as the Brain has been adapted to the New Normal. Other brain areas associated and affected are Amygdala and the Prefrontal cortex.

This is the same reward system that brings high/ pleasure to feel with food, sex, social interaction, etc. Due to the increased amount, they don't feel pleasure with these factors. Repeated use of substances trains the brain to associate the pleasure felt with the high cues and hence this vicious cycle keeps on repeating. Now the person no longer consumes substances to get high but rather to avoid feeling low and face the withdrawal symptoms, this explains why stopping is so difficult.

The Addiction Cycle:

The addiction to drug-taking behavior progresses from impulsivity to compulsivity and has a three-stage cycle:

  • Binge/intoxication stage

The drugs have positive reinforcing effects and they involve actions that are based on inputs from the hypothalamus, which is responsible for regulating emotions and senses and response to stress and reward system. PET scans have shown that intoxicating doses of alcohol and drugs produce opioid and dopamine peptides in the brain. This faster and steep release of dopamine is responsible for the subjective sensation of the so-called hype.

  • Withdrawal/Negative Affect

It is a chronic drug-seeking stage that involves the reduction in the brain's stress neurocircuitry system and the functioning of the extended amygdala system.

  • Preoccupation/Anticipation

It is the craving stage which involves parts of the amygdala (prefrontal cortex and basolateral amygdala) and afferent projections to the nucleus accumbens and amygdala.


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