Substance Dependence: Who, When, and How?

Kirsten Milligan

September 17th, 2019

In April 2016, opioid abuse was declared a public health emergency in BC. Even in controlled medical settings, patients may become addicted to prescribed medications, including pain-relieving opioids such as morphine [1]. On the other hand, in June 2018, cannabis use was legalized in Canada. Consumption of certain substances, such as alcohol (a depressant) and caffeine (a stimulant) is so common that we may not recognize it as ‘substance use’ at all.

Considering this information, it is easy to become overwhelmed with questions such as:

  • When does substance use become substance dependence?
  • How do people become dependent?
  • Can any substance be addictive? Can anyone become dependent on a substance?
  • Is it possible to use substances safely?


When does substance use become substance dependence?

Most people have used a substance at some time during their life, but it is important to recognize the difference between substance use and substance dependence.

According to the most current manual of mental health disorders [2], symptoms of substance dependence includes the following:

  • Continuing substance use despite the problems it causes (e.g., in relationships or at work)
  • Wanting to quit, but unable to stop for any long period of time
  • Developing tolerance (the same amount or concentration of the substance no longer has the same effects)
  • Experiencing cravings and withdrawal symptoms during periods of abstinence
  • Devoting an excessive amount of time to substance use, and continuing even when it becomes dangerous
  • If these symptoms appear, it is possible that substance dependence has developed.


How do people become dependent?

Substance dependence is fed by two major mechanisms:

  • the chemistry within the brain, which physically responds to a drug
  • the learned behaviour of dependence, which includes motivations and habits.

First, substance use can alter our brain chemistry, which may ultimately lead to dependence. Certain chemicals called neurotransmitters are exchanged throughout the systems of the brain, regulating functions such as emotions and perceptions. When substances such as depressants and stimulants enter these systems, they can affect the normal functioning of the brain. Dependence, in particular, tends to be connected to the neurotransmitter dopamine, which is naturally produced in our brains. Dopamine is responsible for positive sensations of reward, as well as the negative sensations of withdrawal [3]. In other words, when substances increase the dopamine in our brains, they provide two reasons to continue using: 1) to re-experience the positive feelings of the drug, and 2) to escape the uncomfortable state of withdrawal.

Second, there are many psychological reasons why people start to use substances. Sometimes, people use substances in order to self-medicate, believing the substance will help them cope with negative experiences or emotions. If someone’s friends or family use substances, this tends to increase the probability of substance use and dependence, as our standards of normal behaviour are often defined by the people closest to us [4].


Can any substance be addictive? Can anyone become dependent on a substance?

Even some of the substances that are legal and considered safe to use, such as caffeine and alcohol, can be addictive. In the DSM-5, caffeine withdrawal has been introduced as a new disorder. As well, alcohol dependence, previously called ‘alcoholism,’ has been established as a disorder for a long time. It is important to remember that most substances can be addictive – however, some drugs are more addictive than others, depending on how they affect the brain.

Likewise, some people are more vulnerable to drug dependence than others. Unfortunately, there is a myth that people who become dependent on drugs are weak-willed or self-indulgent; this is not true. The likelihood that a person becomes dependent on a drug is determined by many factors, including the context in which they are using the drug, their expectations of the drug, their genetics, and their unique brain chemistry.


Is it possible to use drugs safely?

It is always important to understand the risks of the substances you are taking, in order to make informed decisions. It is possible to use some substances safely, when those substances are consumed in low, infrequent doses. Legal substances are often safer because they come from licensed sources, whereas illegal drugs may contain unknown and dangerous ingredients. Moreover, your unique physical reaction to a substance can be unpredictable. As such, it important to create a safety plan when using any type of substance. This can be as simple as calling a friend to drive you home when you feel drunk, or learning how to recognize the symptoms of an opioid overdose and use naloxone (see link below). Regardless of the substance, it is important to be aware of the substance’s effects on your brain, and to recognize the warning signs of dependence and overdose, in order to make sure that you and the people you know are using substances as safely as possible.

If you have reason to believe that you or someone you know is dependent on a substance, do not hesitate to reach out. There are  here.many support groups, such as Alcoholics Anonymous. There are also many resources with information about dependence, such as the American Psychiatric Association.

Lastly, if you are interested in learning how to administer naloxone to counteract an opioid overdose, you can get more information here.




 [1] Compton, W. M., & Volkow, N. D. (2006). Abuse of prescription drugs and the risk of addiction. Drug and Alcohol Dependence, 83

[2] American Psychiatric Association, & American Psychiatric Association. DSM-5 Task Force. (2013). Diagnostic and statistical manual of mental disorders: DSM-5 (5th ed.). Washington, D.C: American Psychiatric Association

[3] Solinas, M., Belujon, P., Fernagut, P. O., Jaber, M., & Thiriet, N. (2019). Dopamine and addiction: What have we learned from 40 years of research. Journal of Neural Transmission, 126(4), 481-516

[4] Soloski, K. L. (2018). Self-medication hypothesis and family socialization theory: Examining independent and common mechanisms responsible for binge drinking. Family Process.

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