About substance use

Information about the stages of substance use, tolerance, dependence, withdrawal and improper use of prescription drugs.

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Substance use spectrum

People use substances, such as controlled and illegal drugs, cannabis, tobacco/nicotine and alcohol for different reasons, including:

  • medical purposes
  • religious or ceremonial purposes
  • personal enjoyment
  • to cope with stress, trauma or pain

Substance use is different for everyone and can be viewed on a spectrum with varying stages of benefits and harms.

Figure: Substance Use Spectrum

The 5 stages of the substance use spectrum

  • Figure – text version

    Stages of the substance use spectrum


    • Avoiding the use of substances (abstinence)
    • For example: No drugs, tobacco or alcohol

    Beneficial use

    • Use that can have positive health, social, or spiritual effects
    • For example: Taking medication as prescribed, ceremonial/religious use of tobacco (such as smudging)

    Lower-risk use

    Higher-risk use

    • Use that has a harmful and negative impact to a person, their family, friends and others
    • For example: Use of illegal drugs, impaired driving, binge drinking, combining multiple substances, increasing frequency, increasing quantity

    Addiction (substance use disorder)

    • A treatable medical condition that affects the brain and involves compulsive and continuous use despite negative impacts to a person, their family, friends and others
    • For example: When someone cannot stop using drugs, tobacco or alcohol even if they want to

    A person may move back and forth between stages over time

Find out more and get a PDF copy of the Substance Use Spectrum.

There are other potential effects associated with the use of substances, including tolerance, dependence, and withdrawal.


When a person who uses drugs or alcohol, becomes accustomed to a particular dose and needs higher amounts in order to obtain the same effects. Tolerance develops over time and will change depending on many factors, such as:

  • age, sex and weight
  • any medical or mental health conditions
  • the amount of the drug consumed
  • the combined use with other substances like:
    • alcohol
    • prescription drugs
    • other illegal drugs
    • over-the-counter medication

People who don't use drugs, or have taken a break from using the drug, may experience lower drug tolerance. This can put them at a greater risk of overdose because they might use more drug than their body can handle.


Physical dependence is a body's natural reaction when certain substances are used for an extended period of time. The body gets used to a regular supply of the substance and, if the dose is lowered or stopped, a person can experience withdrawal symptoms, which can make it difficult to stop using the substance. For some substances, the amount needed to avoid withdrawal increases over time and use as the body develops tolerance.

Someone can be physically dependant on a substance (like a prescription medication) but not use it in a way that has a negative impact to their health or others.


Withdrawal is a natural reaction that may occur when a person reduces or stops taking drugs or alcohol after using regularly for a long time or after using high doses. In some cases and depending on the substance, withdrawal symptoms can be extremely debilitating and make it very difficult to stop or lower the dose.

Symptoms can include:

  • nervousness
  • irritability
  • agitation
  • chills
  • sweating
  • diarrhea
  • nausea
  • stomach pain
  • insomnia
  • body aches
  • widespread or increased pain

Severity and length of withdrawal depends on:

  • which drug was used
  • how much was taken
  • how long the drug or alcohol was used

Prescription drug use and potential harms

Prescription drugs can help treat diseases and conditions, and make you feel better. But taking these medications correctly is important.

Using prescription drugs improperly, like taking medication that has not been prescribed to you or taking more than is prescribed to induce euphoria or change your mood, can have dangerous consequences.

The most common types of prescription drugs that are used improperly include:

  • opioids - prescribed to treat certain kinds of pain
  • benzodiazepines - prescribed to treat anxiety and sleep disorders
  • stimulants - prescribed to treat attention deficit-hyperactivity disorder (ADHD)

Improper use of these medications can cause serious health effects, including addiction (substance use disorder), overdose and even death.

These risks increase when medications are:

  • taken at higher doses than prescribed
  • taken in a different way or for different reasons than they were prescribed
  • used with alcohol or other prescription, over-the-counter or illegal drugs

Learn how to use medications safely and how to safely dispose of prescription drugs.

Negative effects of substance use

Over time, the harms associated with higher-risk substance use may come to outweigh any perceived positive effects. Higher-risk substance use can impact many areas of a person's life:

  • Mental Health
    • Substance use can affect mental health in many ways. It can trigger mood, anxiety or depression disorders. It can also increase the risk of developing a serious mental health illness, such as psychosis or schizophrenia.
  • School
    • Using substances can affect someone's ability to study, to concentrate in class, and to keep up with assignments.
  • Work
    • If someone cannot focus because of their substance use, they might lose their job, hurt themselves or endanger others at work.
  • Relationships
    • Substance use can create an environment of secrecy, conflict, emotional chaos and fear, which can seriously impact surrounding relationships.
  • Money
    • Using substances can be expensive. People might struggle to pay bills or buy the things they need.
  • Mood
    • People may feel good while they use substances, but they feel worse when the effects wear off.
  • Sex
    • Using substances might make people forget to practice safe sex. The result of unprotected sex could be a sexually transmitted diseases or an unwanted pregnancy.
  • Legal problems
    • Illegal sale or possession of drugs can dramatically affect a person's future. If charged and convicted, they will have a criminal record that may present problems with potential employers or when travelling out of the country.
  • Health and safety
    • Heavy use of some drugs and substances don't just affect your brain, it can also damage your physical health and your organs, such as your liver, kidneys and lungs.
    • Sharing drug paraphernalia, such as needles or pipes, can the increase risk of spreading blood-borne infections and other infection diseases like hepatitis C or HIV.
    • Driving impaired by drugs or alcohol puts a person at higher risk of having an accident and getting hurt or hurting someone else.

Wellness and getting help

Getting help can mean different things for different people and it can take many different forms. The chronic nature of addiction (substance use disorder) means that re-using drugs or alcohol at some point, even after a period of non-use, is common.

It's important for people to know that successful treatment is not determined by immediate, long-term abstinence. Treatment is successful when the person understands their addiction and seeks help if re-use occurs. Returning to treatment and healthier behaviours should be considered a success.

Recovery from addiction is possible, but looks different for everyone. People can, and do, overcome substance use issues. A person in recovery is going through an individual process to improve their physical, psychological and social health, which can take time. Recovery could include complete abstinence (avoiding drugs or alcohol completely) or medication assisted treatment, such as prescribing methadone or buprenorphine to treat opioid use disorder.

There are also many health and social services available across Canada including non-medical therapies, such as counselling, or support from people with lived and living experience.

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