Topic Overview

In Canada, about 14 out of 100 teenagers ages 15 to 19 smoke cigarettes.footnote 1 More than 90 out of 100 of these teenagers may develop a lifelong habit of regular smoking.footnote 2

Nicotine is only one of more than 4,000 chemicals in tobacco, but it is the major component that acts on the brain. The lungs readily absorb nicotine from the smoke of cigarettes, cigars, or pipes. The tissues of the mouth can also absorb nicotine when a person smokes cigars or pipes, or chews tobacco.

Nicotine reaches the brain within seconds and has a direct effect on the body for up to 30 minutes. When a person uses tobacco regularly, the levels of nicotine accumulate in the body during the day and persist overnight, exposing the person to the effects of nicotine for 24 hours.

In the body, nicotine acts as both a central nervous system stimulant and sedative. The person immediately feels the stimulant effect and pleasurable sensation. It increases alertness, relaxes muscles, improves memory and attention, and decreases irritability. The stimulant effect causes a sudden increase in blood pressure, breathing rate, and heart rate. The central nervous system stimulation is followed by depression and fatigue, causing the person to want another cigarette.

Nicotine is one of the most addictive substances. Some teenagers show early signs of addiction within days to weeks after starting to smoke. Repeated tobacco use causes a need for increasingly large amounts of nicotine to feel the same effect (tolerance) and withdrawal symptoms if the person tries to quit.

Smoking affects a person's appearance by causing bad breath, yellow teeth and fingernails, and wrinkles. It also affects a person's fitness and stamina level. Tobacco also leads to serious health problems, including:

  • Long-term (chronic) cough, shortness of breath, and wheezing.
  • Increased risk for heart disease, lung and other cancers, stroke, and emphysema.
  • Increased risk among women for having babies with a low birth weight, which may result in the death of the baby. Women who smoke are also at risk for menstrual problems, early menopause, and osteoporosis.
  • Increased risk among men for erection problems.
  • Increased risk for upper respiratory infections like the common cold, the flu, and sinusitis.

Signs of use

  • Cigarette odour on clothing
  • Cigarette or other tobacco product packages or wrappers in wastebaskets
  • Sudden need to go outside or to the bathroom after meals
  • Decrease in appetite



  1. Health Canada (2010). Canadian Tobacco Use Monitoring Survey (CTUMS) 2010. Available online:
  2. Heart and Stroke Foundation (2012). Statistics. Available online:


ByHealthwise Staff
Primary Medical Reviewer Patrice Burgess, MD - Family Medicine
Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer Peter Monti, PhD - Alcohol and Addiction

Current as ofAugust 21, 2015