Table of Contents
Overview – Tobacco/Nicotine
Tobacco/nicotine use is the leading preventable cause of death worldwide, with nearly one-third of the global adult population smoking regularly. Nicotine is the addictive component of tobacco, acting via nicotinic acetylcholine receptors to stimulate dopamine release in the brain’s reward pathways. This explains why tobacco is so habit-forming despite its well-documented and widespread health risks. Understanding the neurobiology, health impacts, and treatment strategies for tobacco addiction is essential for final-year medical students.
Definition
- A smoker is defined as someone who smokes on a daily to weekly basis.
Epidemiology
- Leading preventable cause of death worldwide
- ~33% of adults worldwide smoke
- Early age of initiation → increased risk of lifetime smoking
- ~50% of smokers die from a tobacco-related disease
- More common in:
- Males
- Ages 24–29
- Individuals with low socioeconomic status
- Global smoking rates are declining overall
Tobacco Smoke Composition
- Nicotine → highly addictive compound
- Monoamine oxidase (MAO) inhibitors → inhibit breakdown of:
- Dopamine
- Serotonin
- Noradrenaline
- Epinephrine
- Carbon monoxide → binds haemoglobin more strongly than oxygen → impairs oxygen delivery
- Tar → deposits in lungs (~1 cup per year in pack-a-day smokers)
- Carcinogens → increase risk of:
- Lung, oral, nasal, tracheal, and pancreatic cancers
Health Effects
Cardiovascular
- Atherosclerosis
- Coronary artery disease
- Stroke
- Peripheral vascular disease
Respiratory
Reproductive
- Impaired fertility
- Low birth weight
- Premature birth
Oncology
- Cancers:
- Lung
- Head and neck
- Pancreas
Addiction Mechanism
- Nicotine is a naturally occurring alkaloid and insecticide
- Rapid absorption (even through skin)
- At low doses: mild euphoria; at high doses: parasympathetic toxicity
- Metabolised via cytochrome P450 enzymes
- Mechanism of addiction:
- Nicotine → stimulates nicotinic acetylcholine receptors in the brain
- → triggers dopamine release in the mesolimbic pathway
- → Reinforces pleasurable behaviours
- Dopaminergic reward circuitry is the same one responsible for survival-driven behaviours (eating, reproduction) → difficult to override
- All addictive substances act on this reward pathway
Nicotine Withdrawal
- Due to re-regulation of nicotinic receptors (usually complete in 2–3 weeks)
- Long-term risk of relapse remains
- Symptoms:
- Depressed mood
- Insomnia
- Irritability
- Anxiety
- Poor concentration
- Restlessness
- Bradycardia
- ↑ Appetite & weight
Management
Pharmacological
- Nicotine Replacement Therapy (NRT) (step-down plan):
- Patches
- Gum
- Inhalers/e-cigarettes
- Lozenges
- Sublingual tablets
- Bupropion:
- Atypical antidepressant
- Increases dopamine and noradrenaline levels
- Non-addictive but may have mild withdrawal symptoms
- Varenicline (Champix):
- Partial nicotinic receptor agonist
- Highest efficacy among pharmacological therapies (~16% quit success rate)
- Nicotine Vaccine:
- Still in development
Behavioural
- Motivational interviewing
- Quitline
- Individual counselling
- Craving avoidance strategies
Summary – Tobacco/Nicotine
Tobacco/nicotine addiction stems from powerful dopaminergic reward pathway stimulation, driven by nicotine’s action on nicotinic acetylcholine receptors. The health consequences are vast, including cancer, cardiovascular disease, and chronic lung conditions. Treatment requires a combination of pharmacological support—such as nicotine replacement, bupropion, or varenicline—and behavioural strategies like counselling and motivational interviewing. For a broader context, see our Psychiatry & Mental Health Overview page.