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Recognizing drugs and their effects

General notice

Regulation of cannabis in Québec

Cannabis was legalized on October 17, 2018. To learn more about the legislation on cannabis and health risks of cannabis use, go to the page Cannabis.

Drugs, which include alcohol and cannabis, are ‘psychoactive’ substances. Once absorbed, these substances alter one or more functions of the body and central nervous system. They can affect:

  • Thoughts
  • Emotions
  • Behaviour
  • Mood
  • Multiple organs

Drugs can be:

  • Natural
  • Synthetic (composed of chemical molecules produced in a lab)

It is important to know that street drugs can be mixed with products that are hazardous to health or other drugs. There is no way of knowing what these drugs contain regardless of their shape, colour or origin.

There is so much information circulating about drugs. This information is sometimes accurate, but it can also be far from the truth.

Effects of drugs

Law of effect

Everyone is different. Each person’s body and mental state, the product he or she uses and the context in which it is used influence the overall experience. These elements combine to form the ‘law of effect’.

The law of effect is the result of a combination of 3 factors:

  • The individual
  • The context in which he or she consumes
  • The product or substance being consumed

Each of these 3 factors is linked to different characteristics.

Each time a characteristic associated with one of the factors is modified, the effect of the drug on that person also changes.

Characteristics of the factors of the law of effect

Here are some examples of characteristics associated with the factors of the law of effect:

  • Quantity
    E.g., 1 glass of champagne, 1 case of 12 beers
  • Frequency of consumption
    E.g., every day, on special occasions
  • Quality or purity of product
    E.g., ecstasy cut with methamphetamine
  • Speed of consumption
    E.g., 1 glass of wine with a meal, 5 shooters in an hour
  • Method of consumption
    E.g., smoked, injected
  • Combination of products
    E.g., cannabis and alcohol, medication and MDMA
  • Age
    You are more susceptible to the effects of alcohol and drugs if you use them before you reach adulthood
  • Gender
    The effects of some drugs, alcohol for example, are stronger in women than in men
  • Height and weight
    The less you weigh the more you will be affected by a given amount of drugs
  • Physical condition
    You are more sensitive to drugs if you have an illness such as diabetes or are tired, sick with a cold or suffering from gastroenteritis, etc.
  • State of mind, mood
    Drugs generally intensify any emotions (sadness, depression, etc.) you may feel prior to taking them
  • Place
    E.g., restaurant, bedroom
  • Atmosphere
    E.g., dance party, crying after a breakup
  • Time of day
    E.g., in the morning before going to school or at work
  • Relationships with others
    E.g., with friends you want to impress
  • Conflicts
    E.g., when you are mad at someone

List of drugs and their effects

Drugs are classified according to their effect on the central nervous system. They are divided into 3 categories:

  • Disruptive substances/Hallucinogens
  • Depressants
  • Stimulants 


These drugs typically cause disorientation (distorted sense of space and time). They also affect the senses (sight and touch, for example), which alters perception.


These drugs typically impact the central nervous system, numbing the brain and slowing the body. Some of these drugs can also alter perception.


These drugs typically cause excitement and restlessness.

Last update: September 13, 2017


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