Webb Therapy Uncategorized Neurobiological Mechanisms of Addiction

Neurobiological Mechanisms of Addiction

Addiction is a chronic, relapsing disorder involving changes in brain reward, motivation, learning, stress and executive control systems. While different substances (and behaviours) act through distinct primary mechanisms, they converge on common neurobiological pathways — particularly the mesocorticolimbic dopamine system.

Below is an overview in Australian English of the core mechanisms and then substance-specific and behavioural addiction processes.


Core Neurobiological Pathways in Addiction

1. The Mesocorticolimbic Dopamine System

The central pathway implicated in addiction is the mesocorticolimbic circuit, involving:

  • Ventral tegmental area (VTA)
  • Nucleus accumbens (NAc)
  • Prefrontal cortex (PFC)
  • Amygdala
  • Hippocampus

All addictive drugs increase dopamine transmission in the nucleus accumbens, either directly or indirectly. Dopamine does not simply produce pleasure — it encodes reward prediction, salience and learning. With repeated exposure:

  • Drug-related cues gain exaggerated salience
  • Natural rewards become less reinforcing
  • Behaviour becomes increasingly habitual and compulsive

2. Neuroadaptation and Allostasis

Repeated substance exposure produces:

Tolerance — Reduced response due to receptor downregulation or neurotransmitter depletion.

Dependence — Neuroadaptations that produce withdrawal when the substance is removed.

Allostatic shift — The brain’s reward set point shifts downward, mediated by stress systems (e.g. corticotropin-releasing factor), resulting in dysphoria during abstinence.

3. Habit Formation and Loss of Control

With repeated use:

  • Control shifts from ventral striatum (goal-directed) to dorsal striatum (habit-based)
  • Prefrontal cortex regulation weakens
  • Impulsivity and compulsivity increase

Substance-Specific Mechanisms

Alcohol

Alcohol acts on multiple neurotransmitter systems:

  • Enhances GABA-A receptor function (inhibitory)
  • Inhibits NMDA glutamate receptors (excitatory)
  • Increases dopamine release in nucleus accumbens
  • Affects endogenous opioid systems

Chronic exposure leads to:

  • GABA downregulation
  • NMDA upregulation
  • Hyperexcitable state during withdrawal (risk of seizures, delirium tremens)

Alcohol dependence also involves stress system activation and impaired frontal cortical control.

Methamphetamine

Methamphetamine is a potent psychostimulant that:

  • Enters presynaptic terminals
  • Reverses the dopamine transporter (DAT), causing carrier-mediated dopamine efflux
  • Inhibits vesicular monoamine transporter 2 (VMAT2), releasing dopamine from synaptic vesicles into the cytoplasm
  • Causes massive dopamine release into the synapse

It also increases noradrenaline and serotonin.

Chronic use causes:

  • Dopamine neurotoxicity (particularly to dopaminergic terminals)
  • Reduced dopamine transporter availability
  • Structural changes in striatum and PFC
  • Persistent cognitive deficits

Methamphetamine produces particularly strong sensitisation of cue-driven craving.

Cocaine

Cocaine:

  • Blocks the dopamine transporter (DAT), preventing reuptake
  • Increases synaptic dopamine concentration

Unlike methamphetamine, cocaine acts by blocking DAT rather than reversing it, and does not cause large presynaptic vesicular release — the elevation in synaptic dopamine arises from impaired clearance.

Repeated use leads to:

  • Dopamine receptor downregulation
  • Enhanced cue reactivity
  • Rapid cycling between intoxication and crash
  • Strong psychological dependence

Opioids (e.g. heroin, morphine, oxycodone)

Opioids act primarily at mu-opioid receptors (MORs), which are expressed throughout the brain, including in the VTA. Their dopaminergic effects arise through multiple mechanisms:

  • MORs on GABAergic interneurons in the VTA suppress inhibitory tone, thereby disinhibiting dopamine neurons (the classical disinhibition mechanism)
  • MORs are also expressed on VTA dopamine neurons and projection targets directly, contributing additional excitatory drive beyond the disinhibition pathway

They also act in brainstem respiratory centres, which underlies the risk of respiratory depression in overdose.

Chronic use produces:

  • Receptor desensitisation and internalisation
  • Reduced endogenous opioid production
  • Severe physical withdrawal mediated by noradrenergic rebound in the locus coeruleus
  • Strong negative reinforcement (use to avoid withdrawal)

Cannabis

Δ9-tetrahydrocannabinol (THC):

  • Activates CB1 receptors (the primary psychoactive cannabinoid receptor)
  • Modulates GABA and glutamate release at presynaptic terminals
  • Indirectly increases dopamine in NAc via disinhibitory mechanisms

Cannabis produces:

  • Altered endocannabinoid system function
  • CB1 receptor downregulation with chronic use
  • A mild to moderate withdrawal syndrome (irritability, sleep disturbance, appetite changes)
  • Effects on hippocampal memory circuits

While addiction risk is generally considered lower than for opioids or stimulants, it remains clinically significant and may be underestimated, particularly given the widespread availability of high-potency THC products (e.g. concentrates and high-THC flower), which are associated with greater dependence risk and more severe withdrawal.

MDMA (Ecstasy)

MDMA:

  • Reverses the serotonin transporter (SERT), causing massive serotonin efflux — this is its primary mechanism
  • Also increases dopamine and noradrenaline

Neurobiological consequences include:

  • Acute empathogenic and entactogenic effects driven by serotonin release
  • Post-use serotonin depletion, which may contribute to dysphoria in the days following use
  • Potential serotonergic neurotoxicity, though this evidence comes largely from high-dose or repeated animal studies; the clinical significance in typical human recreational use remains under debate and is not definitively established
  • Moderate addictive potential relative to psychostimulants, partly because dopaminergic effects are less prominent than with cocaine or methamphetamine

Prescription Psychoactive Medications

Certain prescribed medications also have addictive potential:

Benzodiazepines — Enhance GABA-A receptor activity. Cause tolerance via receptor downregulation. Dependence is primarily a GABAergic adaptation. Withdrawal can be protracted and, in cases of high-dose or long-term use, may produce seizures.

Prescription stimulants — Act via similar mechanisms to amphetamine, increasing dopamine and noradrenaline. Risk of misuse exists in susceptible individuals, though therapeutic doses in appropriately diagnosed patients are associated with substantially lower addiction risk than recreational use.


Behavioural (Process) Addictions

Gambling Disorder

Gambling disorder is recognised in DSM-5-TR as a non-substance-related addictive disorder. Although no substance is ingested, similar neurobiological mechanisms are involved.

Dopamine and reward prediction error — Near misses activate the nucleus accumbens similarly to wins. Variable ratio reinforcement schedules (as in poker machines) generate strong, unpredictable dopamine prediction error signalling that powerfully drives continued behaviour.

Cue reactivity — Gambling-related cues activate the same mesocorticolimbic circuitry as drug cues, with increased striatal activation and reduced prefrontal inhibitory control.

Habit circuitry — A shift from ventral to dorsal striatal control contributes to compulsive betting despite continued losses.

Other Emerging Behavioural Addictions

Conditions such as internet gaming disorder, compulsive sexual behaviour disorder, and problematic social media use share overlapping neurobiological features including:

  • Dopamine dysregulation and sensitisation to cue salience
  • Reduced executive control
  • Stress system activation

However, the evidence base for most of these conditions is still developing, and their classification as formal addictive disorders remains an area of active research and debate. Internet gaming disorder is currently listed in DSM-5-TR as a condition for further study.


Shared Neurobiological Themes Across Addictions

Across substances and behaviours, addiction involves:

  • Dopamine sensitisation to cues
  • Reduced sensitivity to natural rewards
  • Impaired prefrontal inhibitory control
  • Stress system overactivation (particularly corticotropin-releasing factor)
  • Habit circuitry dominance (dorsal striatum)
  • Neuroplastic changes in glutamatergic signalling

Why Some Substances Are More Addictive

Addictive potential is influenced by multiple interacting factors. The speed of dopamine rise is one of the most studied — faster onset of dopamine elevation (e.g. via smoking or intravenous administration) is associated with stronger reinforcement. This framework, developed largely through the work of Volkow and colleagues, has strong empirical support, though it represents a mechanistic model rather than an established universal law. Other important factors include:

  • Intensity of dopamine release
  • Pharmacokinetics (e.g. route of administration)
  • Withdrawal severity (which drives negative reinforcement)
  • Social and environmental context
  • Genetic vulnerability (heritability of addiction is estimated at 40–60% across substances)

Conclusion

Addiction is not simply about pleasure seeking. It reflects maladaptive neuroplasticity in reward, stress, learning and executive control circuits. While alcohol, methamphetamine, cannabis, opioids, cocaine and MDMA each act through different primary molecular mechanisms, they converge on common neural pathways that drive craving, tolerance, withdrawal and compulsive use. Behavioural addictions such as gambling engage these same circuits despite the absence of an ingested substance.

The neurobiological understanding of addiction continues to evolve, and where evidence is still emerging — particularly regarding emerging behavioural addictions and the long-term neurotoxic effects of substances like MDMA — clinical interpretation should be appropriately cautious.

Related Post

Mortality DeterminantsMortality Determinants


Overall Global Leading Cause of Death

  • Ischemic heart disease (coronary artery disease) – Still the #1 cause of death worldwide.
  • Followed by: Stroke, chronic obstructive pulmonary disease (COPD), lower respiratory infections, and cancer (e.g., lung, liver, colorectal).

Breakdown by Category

By Age

Age GroupLeading Cause(s) of Death
Infants (<1)Neonatal conditions, birth complications, infections
Children (1–14)Accidents (injuries), infections (low-income countries), cancers (e.g., leukemia)
Youth (15–24)Road injuries, suicide, homicide (varies by country)
Adults (25–44)Injuries (road, drug overdose), suicide, HIV/AIDS (in some countries), heart disease
Middle Age (45–64)Heart disease, cancer (esp. lung, colorectal, breast), liver disease
Older Adults (65+)Heart disease, stroke, cancer, Alzheimer’s disease

By Gender/Sex

GroupLeading Cause of Death
Cisgender MenHeart disease, cancer (lung, liver), accidents
Cisgender WomenHeart disease, cancer (breast, lung), stroke
Transgender IndividualsElevated risk from violence, suicide, and HIV/AIDS (especially trans women of color); limited large-scale data
Non-binaryInsufficient population-specific data, but risks often parallel those of trans populations or assigned sex at birth

By Race/Ethnicity (Example: United States)

GroupTop CausesUnique Issues
White (non-Hispanic)Heart disease, cancer, drug overdose
Black or African AmericanHeart disease, cancer, higher stroke risk
Hispanic/LatinoHeart disease, cancer, diabetes
Native AmericanAccidents, liver disease, diabetes, suicide
Asian AmericanCancer (leading cause), stroke, heart disease

Note: Disparities arise from systemic inequalities, access to care, and social determinants of health.


By Sexuality (LGBTQ+)

  • Limited global data, but in many regions:
    • Higher risk of suicide, mental health disorders, substance abuse, HIV/AIDS (especially among MSM and trans women).
    • Discrimination and healthcare avoidance contribute to worsened outcomes.
  • Common causes of death still include heart disease and cancer, with higher rates of premature death linked to stigma and healthcare disparities.

By Geographic Region

RegionLeading Cause(s)
High-Income CountriesHeart disease, cancer, Alzheimer’s, stroke
Low- and Middle-Income CountriesInfectious diseases (TB, HIV), maternal mortality, stroke, heart disease
AfricaHIV/AIDS, malaria, lower respiratory infections
AsiaStroke, heart disease, chronic lung disease
North AmericaHeart disease, cancer, drug overdose (opioid crisis)
EuropeHeart disease, stroke, cancer
Latin AmericaViolence (in younger adults), heart disease, diabetes

By Profession

  • Agricultural/farm workers: High injury rates, pesticide exposure, suicide
  • Construction workers: Falls, injuries, exposure to toxins (e.g., asbestos)
  • Healthcare workers: Infectious disease, burnout, mental health risks
  • Military/first responders: Combat-related injuries, PTSD, suicide
  • Office workers: Sedentary lifestyle risks (heart disease, diabetes)

Occupation-linked deaths often relate to environmental exposures, physical risks, or psychological stressors.


Conclusion:

Across almost all demographics, heart disease remains the leading cause of death, followed by cancer, stroke, and—in certain populations—accidents, suicide, or infectious diseases. However, the underlying causes (social, economic, political) differ significantly based on identity, geography, and profession.

Would you like this formatted into a chart, infographic, or specific to a country or report you’re working on?

Clinical and Psychiatric Understanding of Religious Extremism and ViolenceClinical and Psychiatric Understanding of Religious Extremism and Violence

Purpose

This report summarises how clinical psychology and psychiatry generally understand people who believe that killing others is justified, necessary or required because of a religious or ideological cause. It uses plain language where possible and distinguishes extreme beliefs from mental illness.

Believe it or not – Key finding

A belief that killing people is justified by religion does not, by itself, mean that a person is mentally ill.

This is an important distinction. Contemporary psychiatric literature indicates that members of terrorist or extremist groups do not generally have higher rates of mental illness than the general population. Mental illness appears to be more common among some lone-actor extremists, but it still cannot be assumed to be the explanation for their behaviour.

In other words, someone can be psychologically capable of understanding what they are doing, planning it deliberately and believing that it is morally right, while not suffering from a psychiatric disorder.

1. Extreme religious belief is not necessarily psychosis

Psychosis involves a significant loss of contact with reality, such as hallucinations or fixed false beliefs that are not reasonably explained by the person’s cultural or religious background.

For example:

  • Extreme ideology: “My religion teaches that these people are enemies of God, so killing them is justified.”
  • Possible psychosis: “God is personally speaking to me through my television and has instructed me to kill my neighbour because he is secretly a demon.”

The first statement may represent an extreme ideological or religious belief. The second could indicate a psychiatric disorder, particularly if it occurs alongside other symptoms of psychosis.

A psychiatrist would therefore ask much more than “Does this person have strange beliefs?” They would examine whether the person has lost the ability to distinguish their beliefs from reality and whether there are other symptoms of mental illness. Distinguishing extremist beliefs from symptoms of mental disorder is recognised as an important difficulty in psychiatric assessment.

2. How can an otherwise ordinary person come to accept killing?

Psychology provides several explanations that do not require mental illness.

One is moral disengagement. This is where a person changes the way they think about an action so that something normally considered wrong becomes acceptable.

An ordinary example would be a soldier being trained to think of an enemy as a threat rather than as an individual person with a family and a life.

In extremist thinking, this can become much more extreme:

“They are not innocent people. They are enemies of God.”

Once someone has been placed into an “enemy” category, killing them can become psychologically easier to justify.

3. The importance of an “us versus them” mentality

Extremist movements often create a very strong distinction between “us” and “them”.

The person may increasingly see:

  • their own group as good, pure or righteous;
  • outsiders as corrupt, dangerous or evil;
  • disagreement as evidence of hostility; and
  • violence as self-defence or moral duty.

This is something ordinary people can recognise in less extreme forms.

For example, football rivalry can involve “us versus them”, but most people retain the understanding that the opposing team’s supporters are still ordinary human beings.

Extremism can take the same psychological distinction to an entirely different level, where the opposing group is no longer regarded as deserving the same moral consideration.

4. Religion can provide a powerful justification

Religious belief can become particularly powerful when something is regarded as a sacred or absolute value.

If a person believes:

“This is God’s command”,

then ordinary moral reasoning can change.

Instead of asking:

“Is killing this person morally acceptable?”

the person may ask:

“How could I disobey God?”

This can produce a situation where the individual genuinely believes they are doing something morally good, despite the fact that an outside observer sees the behaviour as horrific.

That does not make the behaviour acceptable, nor does it make the belief reasonable. It helps explain how the person can psychologically reconcile their actions with their own sense of morality.

5. Believing something and acting on it are different

Clinical assessment is particularly interested in the difference between extreme beliefs and a pathway towards violence.

A person might say:

“I believe people who oppose my religion are evil.”

That is concerning, but it is different from:

“I have decided to kill someone.”

And that is different again from:

“I have chosen a target, obtained the means to do it and have started preparing.”

Psychiatric risk assessment therefore looks for behavioural evidence of movement towards violence, rather than simply diagnosing someone based on their political or religious beliefs. Contemporary forensic psychiatry specifically emphasises identifying warning behaviours and distinguishing extremist beliefs from an actual pathway towards violence.

6. Mental illness can nevertheless be involved

Some people who commit extremist violence do have mental disorders.

For example, a person could have:

  • schizophrenia or another psychotic disorder;
  • severe depression;
  • a personality disorder;
  • substance-use problems;
  • significant paranoia;
  • or another condition affecting their judgement or behaviour.

However, clinicians should not automatically assume that the mental illness caused the extremism.

The relationship may instead look something like:

Personal grievance + extremist ideology + social reinforcement + psychological vulnerabilities + opportunity + willingness to use violence

rather than simply:

mental illness → terrorism.

Research specifically cautions against looking for a single cause or single psychological profile for radicalisation.

7. The most important clinical distinction

From a clinical perspective, there is a major difference between:

“This person believes something that I consider bizarre, frightening or morally repugnant.”

and

“This person has a psychiatric disorder that is causing them to lose contact with reality.”

Those are not the same thing.

A person can be completely sincere, highly intelligent, psychologically organised and fully aware of their actions, while holding an extraordinarily dangerous ideology.

That is one reason psychiatry does not regard terrorism or religious extremism as a diagnosis in itself.

Conclusion

Clinical psychology and psychiatry would generally view religiously motivated killing as a complex interaction between ideology, psychology, social influences and individual circumstances, rather than automatically as evidence of insanity.

The crucial question is not simply:

“Are their beliefs extreme?”

It is:

“What is driving those beliefs, how firmly are they held, is the person able to distinguish belief from reality, and have they moved from believing violence is justified to actually intending, preparing or attempting to carry it out?”

That distinction is important because a mentally ill person is not necessarily dangerous, and a person who is not mentally ill can nevertheless become extremely dangerous. Contemporary psychiatric literature explicitly warns against confusing mental disorder with extremist ideology and instead emphasises assessing the person’s actual pathway towards violence.

Self-sabotage is self-sabotaging. Why would anyone do this?Self-sabotage is self-sabotaging. Why would anyone do this?

As I always like to say, there are as many reasons why people self-sabotage as there are people. A common theme is to protect the self from failure, feeling things we don’t want to feel, and to control our experiences.

One of the hidden culprits behind self-sabotage is the need for perfection and control. Self-sabotage has a strange way of helping us maintain the illusion that if only we had put in more effort or had better circumstances, everything would have worked out as it should. Social psychologists call this counter-intuitive strategy of regulating self-esteem ‘self-handicapping.’ It’s very seductive to engage in self-sabotage because the hidden payoff is high. It’s often easier to be a perfect whole rather than a real part. It’s a short-term solution that sidesteps the more arduous but ultimately more fulfilling work of individuation and self-realization. It takes risk, patience, suffering, and ultimately wisdom to come to the place where you can let go of self-sabotage and learn how to be real.

Behaviour is said to be self-sabotaging when it creates problems in daily life and interferes with long-standing goals. The most common self-sabotaging behaviors include procrastination, self-medication with alcohol and other drugs, comfort eating, and forms of self-injury such as cutting.

Self-sabotage originates in the internal critic we all have, the side that has been internalized by the undermining and negative voices we’ve encountered in our lives. This critic and ‘internal sabotuer,’ functions to keep the person from risking being hurt, shamed, or traumatized in the ways they had been in the past. While it keeps the individual safe, it does so at a very high cost, foreclosing the possibility of new, creative, and three-dimensional experiences. Like an addiction, self-sabotage insidiously lulls and deludes us into thinking that it has the answer. In fact, it is the problem masquerading as the solution. Nothing stops self-sabotage faster in its tracks than shining this particular light on it. Consciousness is true power. We need to let go of our illusions of omnipotence and perfection and see that it is only when we are real and imperfect that we can create a true work of art. Then and only then we can enjoy the gifts of being Real.

– Michael Alcée, Ph.D., Relational therapist/ Clinical psychologistArt: Bawa Manjit, Acrobat

– Self-Sabotage | Psychology Today Australia