Introduction to nicotine

Nicotine is a chemical substance derived from the dried leaves and stems of tobacco plants. It forms one of over 7,000 chemicals present in tobacco smoke and serves as the main agent that influences brain function. Products like smokeless tobacco, such as snuff and chewing tobacco, also contain high levels of nicotine along with various toxins.

Mode of action of nicotine

Nicotine enters the body through various routes and quickly affects the brain by altering neurotransmitter levels.

How nicotine is absorbed and acts

• Absorption methods - Nicotine can be taken in through the skin, the mucosal linings of the nose and mouth, or the lungs via inhalation. For smokers, the lungs absorb it rapidly, allowing it to cross cell membranes and enter the bloodstream.
• Speed of effect - In cigarette smoking, nicotine reaches the brain in as little as ten seconds after inhalation, leading to quick peak levels in the bloodstream.
• Impact on neurotransmitters - Nicotine binds to and activates nicotinic acetylcholine receptors, which are sites on nerve cells that normally bind to acetylcholine. This activation stimulates the release of various neurotransmitters, including dopamine, affecting brain function.
• Further physiological changes - Nicotine increases blood glucose levels, which suppresses appetite.

Effects of nicotine

Nicotine triggers a range of immediate physical and psychological responses in the body.

Physical effects

• Cardiovascular changes - Nicotine leads to a short-term rise in blood pressure, heart rate, and blood flow from the heart. It also narrows the arteries, restricting blood vessel size.
• Oxygen reduction - Carbon monoxide from tobacco smoke decreases the blood's oxygen-carrying capacity.
• Appetite suppression - Nicotine inhibits hunger, which some people mistakenly use as a weight loss method. However, this is not a healthy approach, and quitting often restores normal appetite, potentially leading to weight gain if not managed through diet.

Psychological effects

• Relaxation and euphoria - Users often experience mild relaxation and a sense of euphoria.
• Cognitive improvements - Nicotine can enhance attention and problem-solving abilities in the short term, making tasks feel easier to manage.

Development of tolerance to nicotine

With nicotine, tolerance develops quickly due to repeated exposure.

How tolerance builds

• Rapid metabolism - Nicotine is broken down quickly in the body, often disappearing within a few hours. This leads to a loss of some tolerance overnight, making the first cigarette of the day feel particularly strong.
• Daily cycle - Tolerance increases throughout the day with continued smoking, so later cigarettes have diminished effects. It then decreases again during sleep, creating a cycle that encourages regular use.

Dependency on nicotine

Nicotine creates both physiological and psychological dependencies rapidly.

Physiological dependency

• Acetylcholine adaptation - The surge in acetylcholine from nicotine leads the body to adapt, functioning best when nicotine is present. As blood levels drop, symptoms like irritability emerge, making users feel they need to smoke to restore 'normalcy'.
• Speed of onset - This dependency develops quickly, mirroring the rapid build-up of tolerance.

Psychological dependency

• Oral stimulation - Smokers become accustomed to the physical act of smoking, which can lead to substitutes like increased eating if they quit.
• Reward association - Smoking provides rewards like calmness, encouraging repetition through operant conditioning.
• Quick reinforcement - The fast effects after inhaling act as a strong reinforcer, linking the behaviour to immediate pleasure and making it hard to break the habit.

Withdrawal from nicotine

Common withdrawal symptoms

• Emotional and cognitive effects - Irritability, sleep disturbances, cravings (intense urges for nicotine), and deficits in attention and thinking.
• Physical changes - Increased appetite.
• Duration - Symptoms peak in the first few days and may ease within weeks, but for some, they last months. Cravings can persist for six months or longer.

Factors influencing withdrawal

• Pharmacological basis - Symptoms stem from the body's adjustment to nicotine's effects on neurotransmitters.
• Psychological influences - The severity can also be influenced by psychological factors.

Learning explanations for nicotine addiction

Learning theories explain addiction as acquired behaviours rather than a disease, focusing on reinforcement and observation. These apply to nicotine by highlighting how habits form and persist.

Operant conditioning

Operant conditioning is a learning process where behaviours are shaped by rewards (reinforcers) or punishments.

How operant conditioning applies to nicotine addiction:

• Positive reinforcement - Smoking provides immediate rewards, like relaxation or euphoria, strengthening the behaviour despite long-term risks (e.g., health damage). The quick effects from inhalation make this reinforcement particularly powerful.
• Negative reinforcement - Continued smoking avoids unpleasant withdrawal symptoms, such as anxiety or nausea. For example, as nicotine levels drop, discomfort arises, and smoking removes it, reinforcing the habit.

Social learning theory

Social learning theory proposes that behaviours are learned by observing and imitating others, especially role models.

How social learning theory applies to nicotine addiction:

• Vicarious reinforcement - Seeing family, friends, or high-status individuals enjoy smoking (despite initial unpleasantness) provides indirect rewards, encouraging imitation.
• Group influences - Peers and parents can model smoking, with positive reinforcement from group belonging making the behaviour more likely to repeat.