Sapiens: A Brief History of Humankind.

Addiction fundamentally alters the brain’s reward and decision-making systems through well-documented neurobiological mechanisms. When substances like drugs (including alcohol and nicotine) are consumed, they trigger massive releases of dopamine in the brain’s reward circuit, particularly in areas like the nucleus accumbens and ventral tegmental area. With repeated exposure, the brain adapts by reducing natural dopamine production and decreasing the number of dopamine receptors, creating tolerance and requiring increasingly larger amounts of the substance to achieve the same effect. This neuroadaptation hijacks the brain’s natural reward system, making everyday activities less rewarding while the addictive substance becomes disproportionately important.

Over time, addiction also impairs the prefrontal cortex, the brain region responsible for executive functions like decision-making, impulse control, and weighing long-term consequences. This creates a neurological double-bind: the midbrain structures driving craving and drug-seeking behaviour become hyperactive, while the prefrontal systems that would normally regulate these impulses become weakened. Chronic substance use also disrupts stress response systems, making individuals more vulnerable to relapse during difficult periods. These changes help explain why addiction is recognised as a chronic brain disease rather than simply a matter of willpower – the neuroplastic changes can persist long after substance use stops, though the brain does have remarkable capacity for recovery with sustained abstinence and appropriate treatment.

The Challenge of Stopping

The challenge of stopping stems from the profound neurobiological changes addiction creates in the brain’s fundamental survival systems. The brain essentially learns to treat the addictive substance as necessary for survival, similar to food or water. When someone tries to quit, they face intense physical withdrawal symptoms as their neurochemistry struggles to return to homeostasis, combined with psychological cravings that can persist for months or years. The damaged prefrontal cortex makes it extremely difficult to override these powerful urges with rational decision-making, while stress, environmental cues, and emotional states can trigger automatic drug-seeking responses that feel almost involuntary. This creates a cycle where attempts to quit often lead to temporary success followed by relapse, which many interpret as personal failure rather than recognising it as part of the neurological reality of the condition.

Addiction appears progressive because tolerance drives escalating use over time, while the brain’s reward system becomes increasingly dysregulated. What begins as recreational use gradually shifts to compulsive use as natural dopamine production diminishes and neural pathways become more deeply entrenched. The condition typically follows a predictable pattern: initial experimentation leads to regular use, then to use despite negative consequences, and finally to compulsive use where the person continues despite severe impairment in major life areas. Additionally, chronic substance use often damages the brain regions responsible for insight and self-awareness, making it harder for individuals to recognise the severity of their condition. The progressive nature is also influenced by external factors – as addiction advances, people often lose social supports, employment, and housing, creating additional stressors that fuel continued use and make recovery more challenging.

Understanding addiction when you’re not “addicted” to alcohol or other drugs

The difficulty in understanding addiction, even among people with their own compulsive behaviors, stems from several key differences in how these conditions manifest and are perceived. While behaviors like sugar consumption, social media use, or shopping can indeed activate similar dopamine pathways, they typically don’t create the same level of neurobiological hijacking that occurs with substances like alcohol, opioids, or stimulants. Addictive drugs often produce dopamine surges 2-10 times greater than natural rewards, creating more profound and lasting changes to brain structure and function. Additionally, many behavioral compulsions allow people to maintain relatively normal functioning in major life areas, whereas substance addiction typically leads to progressive deterioration across multiple domains – relationships, work, health, and legal standing.

The social and cognitive factors also create barriers to understanding. Most people can relate to losing control occasionally – eating too much dessert or spending too much time scrolling their phone – but these experiences usually involve temporary lapses that can be corrected relatively easily through willpower or environmental changes. This creates a false sense of equivalency where people think “I can stop eating cookies when I want to, so why can’t they just stop drinking?” They don’t grasp that addiction involves a qualitatively different level of brain change where the substance has become neurobiologically essential, not just psychologically preferred. There’s also often a moral lens applied to addiction that doesn’t exist for other compulsive behaviours – society tends to view overconsumption of legal, socially acceptable things as personal quirks or minor character flaws, while addiction to illegal substances or excessive alcohol use carries heavy stigma and assumptions about moral failing, making it harder to see as a medical condition requiring treatment rather than simply better self-control.

A Word On Nicotine (Tobacco Products)

Yes, nicotine absolutely does release large amounts of dopamine, making it highly addictive despite being legal and socially accepted in many contexts. Nicotine causes an increase in dopamine levels in the brain’s reward pathways, creating feelings of satisfaction and pleasure.Research shows that nicotine, like opioids and cocaine, can cause dopamine to flood the reward pathway up to 10 times more than natural rewards.

This helps explain why nicotine addiction can be so powerful and difficult to overcome, even though people often view smoking or vaping as less serious than other forms of substance addiction. Repeated activation of dopamine neurons in the ventral tegmental area by nicotine leads not only to reinforcement but also to craving and lack of self-control over intake. The addiction develops through the same basic mechanisms as other substances – as people continue to smoke, the number of nicotine receptors in the brain increases, requiring more of the substance to achieve the same dopamine response.

What makes nicotine particularly insidious is its legal status and social acceptance, which can make people underestimate its addictive potential. The rapid delivery of nicotine to the brain (within 10-20 seconds when smoked) creates an almost immediate reward that strongly reinforces the behaviour. This is why many people who successfully quit other substances still struggle with nicotine, and why nicotine addiction often serves as a gateway that primes the brain’s reward system for addiction to other substances.

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.