2.3 Why do people continue to use substances

Why do people continue to use substances, as part of a substance use disorder?  You may think of substance use as a habit, as something that gets reinforced through daily repetitions and habits.

Food For Thought

  • Reflect on a “normal day”.  What do you do from the moment you wake until the moment you go to sleep?  Are any of these activities’ habits?
  • Identify the habits you have?
  • Do you think these are healthy or unhealthy habits?  Why do you believe this to be so?
  • How does this habit make you feel?  Why?
  • Have you ever tried to change a habit?  Were you successful?  How?
  • Reflect on a negative habit you currently have.  Where does this habit come from?  What does this habit solve for you?  Have you ever thought about changing it?  What would it take to change it?

A substance use disorder is an unhealthy habit and every time a person uses a substance (repetition) it causes a reaction in both the body (physical) and the mind (psychological).  The substance use is pleasurable, and the repetition can work like an enforcer, drilling those habits deeper and deeper. In time, through the repetition of use and the reinforcement of the habit, this can make the substance use a very difficult habit to break. The habit may become both physical and psychological.

2.3A Activities

  1. Brainstorm all the ways you think a person can become physically dependent on a drug and review with your class.
  2. Brainstorm all the ways you think a person can become psychologically dependent on a drug and review with your class.
  3. Compare and contrast your ideas from your brainstorm.

What is physical dependence?

What is physical dependence? Physical dependence is “a physiological state of cellular adaptation occurring when the body becomes so accustomed to a drug that it can only function normally when the drug is present”. [1]  This means without the substance in the body, the body simply does not function “normally”.  When someone experiences these symptoms, it is called withdrawal.  This can include shaking or trembling, nausea, cramping, muscle spasms and more.  People who have a substance use disorder may experience withdrawal, “the development of physical disturbances or physical illness when drug use is suddenly discontinued in the opposite direction to the original effects of the drug”. [2]  This is the body’s physical response to the absence of the drug.  Withdrawal can range from discomfort to death, depending on the physical dependence (how long a person was using a substance, how often) and the type of substance a person is using.  All these factors will impact their withdrawal, for example, withdrawal from opioids is different than withdrawal from alcohol.  When working with people in withdrawal, it is important to remember it is painful, for both physical and psychological reasons.

With physical dependence also comes tolerance.  Tolerance is the “body’s adaption to the presence of the drug requiring increased amounts to produce the same outcome as originally experienced.[3]  This means that over time it takes more of the substance or drug to produce the same feeling.  This has been known as “chasing the dragon”.

2.3B Activities

  1. Brainstorm a comprehensive list of factors that impact tolerance.
  2. Why do you believe some people develop a tolerance to substances quicker than others?  Discuss with your classmates.

What is psychological dependence?

What is psychological dependence?  Individuals who have a substance use disorder may also develop a psychological dependence.  When you reviewed the activity exploring your habits, perhaps you determined a habit you engage in makes you feel happy.  A psychological dependence is the “mind need” for a substance, “a drug becomes so important to a person’s thoughts or activities that the person believes that he or she cannot manage without the substance”. [4] There is also the belief that persons with substance use disorders

suffer in the extreme with their feelings, either being overwhelmed with painful affects or seeming not to feel their emotions at all. Substances of abuse help such individuals to relieve painful affects or to experience or control emotions when they are absent or confusing.[5]

In this case, a person simply wants to numb their emotional pain and knows that by using and continuing to use a substance their pain can be numbed.  Psychological dependence is just as intense as physical dependence, if not more so.  If you believe you need a particular substance to manage your daily life, the withdrawal from that substance can be difficult.

2.3C Activities

  1. What have you heard about withdrawal?
  2. What types of substances do you think create physical withdrawal?
  3. What types of substances create psychological withdrawal?
  4. Do you think physical or psychological is more intense?  Why?

Both physical and psychological withdrawal may be reasons why a person continues to use substances, and /or experiences a substance use disorder.  According to the American Psychiatric Association[6] to diagnose a substance use disorder a person must have dependence and have experienced withdrawal.  This would include substances like alcohol, heroin, cocaine, and even cannabis, which was a recent addition to the DSM-V.   Withdrawal, both physical and psychological can be quite painful, particularly for people who are using opiates.  Let’s watch the John Lenec discuss his experiences with opioid use and withdrawal.[7] Note the language used by the Canadian Press.  How might you change this language to reduce stigma?


What did you notice?  What were the physical symptoms of withdrawal John discussed?  What were the psychological symptoms of withdrawal John mentioned?  The symptoms of withdrawal may prevent some people from reducing or stopping their substance use.  The table below indicates a number of substances.  Please review the types of dependence for the most commonly used substances.

Psychoactive Substances Dependence Chart[8]
Drug Dangers and Side Effects Psychological Dependence Physical Dependence Potential for Disorder
Caffeine May create dependence Low Low Low
Nicotine Has negative health effects if smoked or chewed High High High
Cocaine Decreased appetite, headache Low Low Moderate
Amphetamines Withdrawal accompanied by severe “crash” (depression) as effects wear off, particularly if smoked or injected Moderate Low Moderate to High
Alcohol Impaired judgment, loss of coordination, dizziness, nausea, and eventually a loss of consciousness Moderate Moderate Moderate
Barbiturates and benzodiazepines Sluggishness, slowed speech, drowsiness, in severe cases, coma or death Moderate Moderate Moderate
Toxic inhalants Brain damage and death High High High
Opium Side effects include nausea, vomiting, tolerance, and addiction. Moderate Moderate Moderate
Morphine Restlessness, irritability, headache and body aches, tremors, nausea, vomiting, and severe abdominal pain High Moderate Moderate
Heroin All side effects of morphine High Moderate High
Marijuana Mild intoxication; enhanced perception Low Low Low
LSD, mescaline, PCP, and peyote Hallucinations; enhanced perception Low Low Low

It is important to note cannabis is not indicated above; however, in the DSM-V it is included as a substance with psychological dependence as people can experience withdrawal.  Were you surprised by any of the states of dependence for any of the substances? The dependence on a substance is one factor that can keep people in a cycle of use.  Uncomfortable withdrawal may make it difficult to go to school, work, or take care of a family.  In some cases, it is extreme, as mentioned in the video.

Are you a regular coffee drinker?  Have you ever tried to give up coffee?  Did you experience any symptoms?  Do you smoke tobacco?  Have you tried quitting?  What was that like?  When we think about substance use and withdrawal, we may immediately go to substances we see in the media, like heroin and cocaine.  It is important to note, based on the chart above, every substance is different, and psychological and physical dependence will be experienced differently depending on the substance and the person who uses it.

2.3D Activities

  Based on what you learned about physical and psychological dependence, as well as all the reasons people use substances, brainstorm:

  1. Reasons why individuals start using substances
  2. Reasons why individuals continue/maintain use
  3. Reasons why individuals escalate/increase frequency or amount of substance use
  4. Reasons why individuals stop using substances
  5. Reasons why individuals start using substances again
  6. Group reasons in two charts, positive and negative.
  7. Identify 1 resource that could provide support for each reason.

All substances have some risk, as they impact our body and brain in different ways.  In Chapter 3 we will examine the various substances, their origins and their impact on the body and mind.

Chapter Credit

Adapted from Unit 5.2 in Drugs, Health & Behavior by Jacqueline Schwab, licensed under a CC BY-NC-SA license.

Updated with Canadian Content.

  1. Csiernik, R. (2015). Substance use and abuse: Everything matters (2nd ed.), (pp 19).  Canadian Scholars Press.
  2. Ibid, p. 31
  3. Ibid, p. 29
  4. Ibid, p. 20
  5. Khantzian, E. J. (1997).  The self-medication hypothesis of substance use disorders: A reconsideration and recent applications.  Harvard Review of Psychiatry, 4(5) 231-244. https://pubmed.ncbi.nlm.nih.gov/9385000/
  6. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596
  7. Canadian Press. (2016, December 21). You think you’re dying’: Ex-Heroin user on withdrawal. [Video]. YouTube. https://youtu.be/Zks_fdt-aHY
  8. Schwab, J. (2021). Drugs, health & behaviour.  Pressbooks. https://psu.pb.unizin.org/bbh143/chapter/altering-consciousness-with-psychoactive-drugs/


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