20.10 — Addiction and Dependence

In the 1970s, a series of experiments put rats in bare cages with two water bottles, one laced with an opioid. The rats drank themselves to death, and the finding was taken to show that the drug was irresistible.

Then someone built a different cage — with space, wheels, tunnels and other rats — and the same drug was taken far less.

The experiment has real methodological limits, and it has been over-quoted. But the direction it pointed has held up: addiction is not simply a chemical hooking a brain. It is a chemical, a brain, and a life, interacting.

Which is why the treatments that work address all three, and why willpower-only approaches have such poor results.

What addiction does to the brain

The reward system exists to make you repeat things that help you survive — eating, drinking, sex, social connection.

Dopamine release in the nucleus accumbens marks something as worth doing again (Chapter 11.5).

And a critical correction to the usual account: dopamine is not the pleasure signal. It is the wanting signal.

Which explains the single most confusing thing about addiction: people continue using long after they stop enjoying it. The wanting system and the liking system are separate, and addiction amplifies wanting while liking fades.

Addictive drugs release far more dopamine than natural rewards — several times more, and faster.

Then the brain adapts. Receptors are downregulated. Baseline dopamine function falls.

Which produces both halves of the trap: tolerance, so more is needed for the same effect, and anhedonia, so ordinary pleasures stop registering. The drug becomes the only thing that reaches the baseline that used to be free.

And the prefrontal cortex — the region that weighs consequences and inhibits impulses — is impaired by chronic use (Chapter 11.5). So the braking system is damaged at the same time the accelerator is stuck.

This is why "just stop" fails, and why relapse is a feature of the condition rather than a moral failure.

Cues matter enormously. The places, people, sights and smells associated with use acquire the ability to trigger craving directly, which is why someone stable for years can be floored by walking down a particular street. Cue exposure explains most relapse better than withdrawal does.

Dependence, tolerance and addiction are not the same thing

And confusing them causes real harm.

Tolerance — needing more for the same effect. Physiological, and it happens with many drugs that are not addictive.

Physical dependence — withdrawal symptoms on stopping. Also physiological. Someone on long-term steroids, beta blockers or antidepressants is physically dependent and is not addicted.

Addiction — compulsive use despite harm, loss of control, craving, and the life narrowing around the substance.

A person with cancer pain on long-term opioids is dependent and usually not addicted. Confusing the two has caused patients to be denied pain relief, and it is worth being precise about.

The substances

Alcohol

The most harmful drug at population level in most countries, because of how widely it is used.

Withdrawal is dangerous, and this is the most important safety point in the chapter.

Alcohol enhances GABA, the brain's main inhibitory signal, and blocks glutamate, the main excitatory one (Chapter 11.2). The brain compensates by reducing GABA function and increasing glutamate.

Remove the alcohol suddenly and that compensation is unopposed — the brain is left over-excited.

The timeline: tremor, sweating, anxiety and nausea from 6 to 12 hours. Seizures at 12 to 48 hours. Delirium tremens at 48 to 72 hours — confusion, hallucinations, severe agitation, fever and dangerous swings in heart rate and blood pressure.

Untreated delirium tremens has a mortality of around 15 percent; treated, under 5 percent.

So: a heavy daily drinker should not stop abruptly without medical support. This is the opposite of the advice for most substances, and it is the one that saves lives.

Treatment of withdrawal: a benzodiazepine on a reducing schedule, plus thiamine, given before any glucose.

And the reason matters: thiamine deficiency causes Wernicke's encephalopathy — confusion, unsteadiness and eye movement abnormalities — which progresses to permanent memory loss if untreated. Giving glucose to a thiamine-deficient person can precipitate it, which is why thiamine goes first.

Longer-term treatment: acamprosate, reducing craving; naltrexone, blocking opioid receptors and reducing the reward from drinking; disulfiram, causing an unpleasant reaction if alcohol is taken, effective when supervised; and psychological treatment plus mutual aid groups.

Physical harm: liver disease (Chapter 21.2), pancreatitis, several cancers, cardiomyopathy, neuropathy, brain damage, and injury.

Nicotine

Around 8 million deaths a year worldwide.

Extremely addictive — reaching the brain within seconds of an inhalation, which produces very tight learning between the act and the reward.

And the good news is substantial: quitting at any age adds years, and quitting before 40 avoids almost all of the excess mortality.

What works: varenicline, the most effective single drug; nicotine replacement, and combining a patch with a fast-acting form works better than either alone; bupropion; behavioural support, which roughly doubles the success of any drug; and e-cigarettes, which trials have found more effective than nicotine replacement for quitting.

On e-cigarettes, the accurate position: substantially less harmful than smoking for someone switching completely, not harmless, and not for people who do not already smoke — particularly adolescents.

And a fact worth holding: most people who quit needed several attempts. A failed attempt is data, not evidence that it cannot be done.

Opioids

Heroin, and prescription opioids including oxycodone, morphine, tramadol and codeine.

Overdose kills by suppressing the brainstem respiratory drive (Chapter 11.7) — breathing slows and stops while the person is unconscious.

The signs: unresponsive, very slow or absent breathing, and pinpoint pupils.

Naloxone reverses it within minutes. It is safe, it is given by injection or nasal spray, it can be given by a bystander, and it does not harm someone who turns out not to have taken opioids. Take-home naloxone programmes save lives and should be as normal as a fire extinguisher in the households that need them (Chapter 23.6).

And a lethal detail: tolerance falls fast after a period of abstinence. Deaths cluster in the weeks after leaving prison or completing detox, because the person takes their previous dose into a body that can no longer handle it.

Which is why detox alone, without ongoing treatment, is worse than no treatment for opioid dependence.

Treatment that works: opioid substitution with methadone or buprenorphine.

And the evidence here is unusually strong: substitution treatment reduces mortality by around half, reduces transmission of blood-borne infection, reduces crime, and keeps people in contact with services.

It is frequently criticised as "replacing one drug with another", and the answer is that the outcome measured is people staying alive. A stable dose taken orally on a schedule does not produce the intoxication, the risk or the chaos, and it allows a life to be rebuilt.

Naltrexone — blocking opioid effects, for people who are already abstinent.

Stimulants

Cocaine, amphetamines, methamphetamine.

Physical withdrawal is mild; the psychological pull is severe, with exhaustion, depression and intense craving.

No effective substitution treatment exists, which is a real gap.

What works is psychological, and contingency management — providing tangible rewards for verified abstinence — has the best evidence of anything for stimulant use. It is under-used because it looks like paying people to do what they should do anyway, which is a values objection rather than an evidence one.

Physical risks: heart attack, stroke, arrhythmia, and psychosis.

Cannabis

Dependence occurs in around 9 percent of users overall, and higher with adolescent onset and daily use.

Withdrawal is real — irritability, poor sleep, reduced appetite, and craving, peaking in the first week.

Risks: psychosis in vulnerable people (Chapter 20.9), impaired driving, and possible effects on adolescent cognitive development, where the evidence is real but not as strong as sometimes claimed.

Benzodiazepines and sedatives

Dependence develops within weeks.

Withdrawal can include seizures and is potentially dangerous, like alcohol and for the same reason.

Stopping requires a slow taper over months, frequently after switching to a longer-acting drug. Abrupt stopping is unsafe.

Behavioural addictions

Gambling disorder is a recognised condition using the same reward pathways, and gambling produces the same dopamine dynamics without any substance, which is strong evidence that the pathway rather than the chemical is the essential thing.

Modern designs — near misses, variable rewards, losses disguised as wins — are engineered around the same principles.

Gaming disorder is recognised, applied to a small proportion of heavy players.

And treatment is the same shape: CBT, self-exclusion schemes, and naltrexone, which has evidence in gambling — the same drug used for alcohol, which again points to a shared mechanism.

What actually helps

Treating it as a health condition rather than a moral failure, because that framing determines whether people seek help.

Motivational interviewing — working with ambivalence rather than confronting it. Confrontational approaches perform worse in trials.

CBT and relapse prevention — identifying triggers, planning for high-risk situations, and treating a lapse as information rather than as proof of failure.

Mutual aid groups — 12-step programmes have better evidence than commonly assumed, particularly for sustained abstinence in alcohol dependence. Secular alternatives exist and work for people whom the 12-step framing does not suit.

Contingency management, particularly for stimulants.

Medication where it exists — and it exists for alcohol, opioids and nicotine.

Harm reduction: needle exchange, naloxone, drug checking, supervised consumption. These reduce deaths and infections without increasing use, which is a well-replicated finding.

And treating what is underneath. Rates of trauma, depression, anxiety and ADHD are high in addiction, and treating only the substance while leaving the reason untouched has poor results.

Housing, work and relationships. The strongest predictors of sustained recovery are stable housing, meaningful occupation and supportive relationships — which is where the different cage comes back in, and which is why treatment that ends at the clinic door underperforms.

The realistic picture

Relapse is common and it is part of the condition, not the end of treatment. Chronic conditions like diabetes and asthma have comparable rates of return to poor control after treatment lapses, and nobody calls those treatment failures.

Most people who recover do so — the majority of people who have ever met criteria for a substance use disorder are in remission, and a large proportion recover without formal treatment.

Which is the fact most worth carrying out of this chapter, because the visible cases are the ones who do not recover, and that produces a badly distorted impression of the odds.

What the next page fixes

Chapter 20.11 covers sleep — the biological function most consistently sacrificed and the one whose loss touches everything else in this Part.