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Before any model of why people become addicted can be evaluated, the phenomenon itself must be carefully described. Addiction is a chronic, relapsing condition in which an individual engages compulsively in a behaviour or in substance use despite harmful consequences. Describing it accurately means distinguishing physical from psychological dependence, understanding the closely related processes of tolerance and withdrawal, and identifying the risk factors that make some individuals more vulnerable than others — genetic vulnerability, stress, personality, and family and peer influences. Throughout this lesson the AQA-specified examples of smoking (nicotine), alcohol and gambling are used, because they let us see how the same descriptive concepts apply both to a substance addiction and to a behavioural one. The topic is treated as a clinical and scientific subject: addiction is described objectively, without glamorising substance misuse and without operational detail, in the standard register of A-Level teaching.
Key Definition: Addiction is a chronic, relapsing condition characterised by compulsive engagement in substance use or a behaviour, continued despite harmful consequences, typically involving dependence and long-lasting changes to the brain's reward, motivation and memory systems.
This lesson addresses the following points from the AQA A-Level Psychology (7182) specification, Paper 3, Section D — Addiction:
It develops precise definitions of dependence, tolerance and withdrawal, applies them to smoking, alcohol and gambling, and explains each named risk factor, preparing you to describe (AO1) and evaluate (AO3) the description of addiction. Questions on this material are usually split AO1/AO3 only, with no AO2 unless a scenario stem describing a particular individual is provided — this lesson flags that distinction. The content underpins the biological, learning and cognitive models that follow, since each of those models is an attempt to explain the descriptive features set out here.
The single most important descriptive distinction is between physical and psychological dependence. They frequently co-occur, but they are conceptually different and have different implications for withdrawal and treatment.
| Feature | Physical Dependence | Psychological Dependence |
|---|---|---|
| Core idea | The body has physiologically adapted to the substance, so removing it disrupts normal functioning | A compelling subjective need for the substance or behaviour to feel normal or to cope emotionally |
| Hallmark features | Tolerance and a physical withdrawal syndrome | Craving, preoccupation, compulsive use, loss of control |
| Withdrawal | Physical symptoms (e.g., tremor, sweating, nausea — and, for alcohol, potentially seizures) | Predominantly psychological symptoms (anxiety, restlessness, low mood, irritability) |
| Typical examples | Alcohol, nicotine, heroin, benzodiazepines | Gambling; also a major component of nicotine, alcohol and cocaine use |
A crucial point for evaluation is that the two forms of dependence are not neatly separable. Nicotine, for example, produces both a genuine physical withdrawal syndrome and powerful psychological dependence (cravings cued by routines and emotions). Gambling is especially instructive: because no substance is ingested, gambling dependence has often been treated as purely psychological — yet gamblers report craving, develop a kind of tolerance (needing to bet larger sums for the same excitement), and experience withdrawal-like restlessness and irritability when they try to stop, which is one reason gambling disorder is now grouped with the substance addictions.
Applying the distinction to the three AQA examples clarifies it. With smoking, the physical component is real (nicotine withdrawal: irritability, poor concentration) but relatively mild and short-lived, whereas the psychological component — cravings triggered by the morning coffee, the work break, stress, or finishing a meal — is often what makes quitting so hard and relapse so common. With alcohol, physical dependence can be pronounced (tolerance and a withdrawal syndrome that, in severe dependence, can be medically serious), and it coexists with strong psychological dependence (drinking to cope, to socialise, to relax). With gambling, there is essentially no chemical and so the physical-dependence component is weak at most, yet the psychological dependence — preoccupation, craving, chasing losses, a felt inability to stop — is profound. The lesson is that physical and psychological dependence vary in their relative weight across addictions but both are typically present to some degree.
Key Definition: Physical dependence is a state in which the body has adapted to a substance such that reducing or stopping it produces a physical withdrawal syndrome. Psychological dependence is a compelling subjective need to use a substance or perform a behaviour in order to feel normal or to manage emotional states.
It also helps to distinguish use, misuse and dependence, since not all substance use is addiction. Use is simply consuming a substance; misuse is using it in a harmful or hazardous way (e.g., heavy episodic drinking) without necessarily being dependent; and dependence/addiction adds the features of tolerance, withdrawal, craving and impaired control that this lesson describes. The same activity can therefore sit at different points on this continuum for different people, which is why addiction is defined not by the substance or behaviour itself but by the pattern of compulsive, harmful, dyscontrolled engagement around it. This continuum view also makes clear that the boundary between heavy use and addiction is a matter of degree rather than a sharp line — a point that becomes important when evaluating how addiction is diagnosed and described.
Tolerance is a physiological adaptation in which increasing doses of a substance are needed to achieve the effect once produced by a smaller dose — or, equivalently, a given dose produces a progressively smaller effect. It is a defining feature of physical dependence and a key driver of escalating use.
Several mechanisms contribute:
Tolerance is not all-or-nothing and can differ across the various effects of a single drug. Critically, tolerance helps explain why dependence tends to escalate: as the brain adapts, the individual needs more of the substance simply to feel its effects, which in turn deepens the physiological adaptation.
Across the examples, alcohol shows clear tolerance — the experienced drinker needs more to reach the same effect, partly through faster metabolism (metabolic tolerance) and partly through nervous-system adaptation (pharmacodynamic tolerance). Nicotine also produces tolerance, especially early in a smoking career, contributing to the rise in daily consumption. Even gambling shows a tolerance-like escalation: the same stake stops producing the original level of excitement, so the gambler bets larger sums or takes greater risks to recapture the "buzz" — a behavioural parallel to drug tolerance that again shows why gambling is described in the addiction vocabulary.
A withdrawal syndrome is the cluster of unpleasant physical and psychological symptoms that appears when a substance is reduced or stopped after the body has become physically dependent on it. Withdrawal symptoms are, characteristically, roughly opposite to the acute effects of the substance: a drug that calms tends to produce agitation on withdrawal, and a stimulant tends to produce fatigue and low mood. This "rebound" pattern reflects the brain's adaptation to the substance being suddenly unopposed.
| Substance | Acute effect | Typical withdrawal features |
|---|---|---|
| Nicotine | Mild stimulation, alertness, relaxation | Irritability, anxiety, restlessness, difficulty concentrating, low mood, strong craving |
| Alcohol | Sedation, reduced anxiety, disinhibition | Anxiety, tremor, sweating, nausea; in severe dependence, potentially serious complications |
| Gambling (behavioural) | Excitement, arousal, "buzz" | Restlessness, irritability, preoccupation and craving when trying to cut down |
The avoidance of withdrawal is one of the most powerful forces maintaining an addiction: the individual increasingly uses the substance not to feel good but simply to feel normal and to escape the aversive withdrawal state — a transition from positive to negative reinforcement developed further in the learning model.
Key Definition: Withdrawal syndrome is the set of physical and psychological symptoms — often opposite in character to the substance's acute effects — that occurs when a substance is reduced or stopped after physical dependence has developed.
Not everyone who encounters an addictive substance or activity becomes addicted. The AQA specification identifies a set of risk factors that increase vulnerability. It is important to be clear that these are risk factors, not causes: they raise the probability of addiction but do not determine it, and they interact (a diathesis–stress logic).
graph TD
A[Risk Factors for Addiction] --> B[Genetic Vulnerability]
A --> C[Stress]
A --> D[Personality]
A --> E[Family Influences]
A --> F[Peers]
B --> H[Increased Vulnerability to Addiction]
C --> H
D --> H
E --> H
F --> H
Family, twin and adoption studies consistently indicate a substantial heritable component to addiction, with heritability estimates commonly in the region of 40–60% depending on the substance. Identical (MZ) twins show higher concordance for addiction than non-identical (DZ) twins, and adoption studies show raised risk in the biological children of addicted parents even when reared apart, pointing to genetic rather than purely environmental transmission. Candidate genes — notably variants affecting the dopamine system, such as the DRD2 receptor gene — have been implicated, though addiction is polygenic: many genes each make a small contribution and no single "addiction gene" exists. Genetic vulnerability is best understood as a predisposition that interacts with environmental exposure. It may operate in several ways: genes can influence how rewarding a substance feels (for instance, through dopamine-receptor density), how quickly a substance is metabolised, and broader temperamental traits such as impulsivity and sensation-seeking that themselves raise risk. In other words, "inheriting a vulnerability to addiction" rarely means inheriting a switch for a specific drug; it usually means inheriting features of the reward system, metabolism or temperament that make dependence more likely once exposure occurs.
Chronic stress and adverse experiences — including childhood trauma and adversity — are strongly associated with addiction risk. Two mechanisms are usually proposed. First, the self-medication account: individuals use substances or behaviours to relieve the unpleasant emotional states stress produces, so the substance is negatively reinforced by stress reduction. Second, stress has biological effects on the reward and stress-response systems that may heighten vulnerability and the risk of relapse: sustained activation of the hypothalamic–pituitary–adrenal (HPA) axis and elevated stress hormones interact with the dopamine reward system in ways that can intensify the reinforcing effects of substances and the pull of craving. Adverse childhood experiences are particularly important because they combine chronic early stress with disrupted family environments, so the stress and family risk factors often act together. Stress is also one of the most reliable triggers for relapse in people who have stopped, which is why stress management features prominently in treatment.
Certain personality characteristics are associated with raised vulnerability. The most-cited is sensation-seeking — Zuckerman's (1979) trait describing a need for novel, varied and intense experiences and a willingness to take risks to obtain them. High sensation-seekers are drawn to the arousal and stimulation that substances and gambling provide. Other dispositional features associated with addiction risk include high impulsivity (difficulty resisting immediate rewards) and, in some accounts, traits linked to neuroticism or to an "addiction-prone" pattern. As with the other factors, personality is a vulnerability rather than a guarantee, and the direction of causation is not always clear.
The family contributes to addiction risk through several routes that are difficult to disentangle: genetic transmission (children inherit predisposing genes from addicted parents), social learning (children observe and may imitate parental substance use — see the learning model), and the family environment more broadly (parenting style, supervision, conflict, attitudes towards substances, and exposure to substances in the home). Perceived parental approval or normalisation of use, and low parental monitoring, are associated with earlier initiation and greater risk.
Peer influence is particularly potent during adolescence, when the desire for social acceptance is strong and the brain's reward system is highly responsive while the prefrontal control system is still maturing. Adolescents whose friends use substances are markedly more likely to initiate use themselves, through direct social pressure, modelling, and the shaping of norms (beliefs about how common and acceptable use is). Peer influence interacts with personality and family factors — for example, a sensation-seeking adolescent with low parental monitoring may both select substance-using peers and be more influenced by them, illustrating how the risk factors combine rather than act in isolation.
Gambling disorder is the principal recognised behavioural addiction and a valuable test case for the descriptive concepts above, because it shows that addiction need not involve a chemical taken into the body. Gambling is associated with craving and preoccupation (psychological dependence), a form of tolerance (needing to wager more to achieve the same level of excitement), and withdrawal-like restlessness and irritability on attempting to cut down. Its reclassification alongside the substance addictions reflects evidence that it engages the same dopamine reward pathways as drug addictions (developed in the biological model). Describing gambling in the same vocabulary of dependence, tolerance and withdrawal is therefore not loose analogy but a recognition of genuinely shared features — though, as evaluation will note, the physical dependence component is far weaker than for alcohol or nicotine.
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