Read also: The Addiction Cycle

Definition of addiction

Addiction is an irrepressible and uncontrollable need to use a substance or perform certain activities. When the need is satisfied, this provides pleasure. When it is not, this provokes a craving, the consequences of which may be more or less serious depending on the level of a person’s addiction.

The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders), a reference manual, has discontinued the use of the terms addiction and abuse in favour of “use disorder.” This disorder varies from “mild” to “moderate” to “severe,” depending on the number of symptoms a person experiences.

Various forms of addiction

While addiction is often associated with the use of psychoactive substances (alcohol, drugs, medication, tobacco, etc.), other forms of behavioural addiction also exist:

  • Gambling
  • Sports activity
  • Sex
  • Technology (cell phones, social networks, etc.)
  • Shopping (compulsive purchases, hoarding, etc.)
  • Food
  • Emotional addiction
What is a psychoactive substance?

According to the World Health Organization (WHO), “Psychoactive substances are substances that, when taken in or administered into one’s system, affect mental processes, e.g., cognition or affect.” These substances may cause feelings of relaxation, euphoria and the loss of inhibitions, as well as more intense effects such as hallucinations.

The reward circuit

Addiction occurs when the reward circuit is disrupted. What is this reward circuit?

When we perform a pleasant task, the brain produces dopamine, among other effects. Dopamine is one of the molecules responsible for the sensation of pleasure, which is why it is called the “pleasure molecule.” This molecule is a neurotransmitter secreted by the body when certain actions are performed: this is the reward circuit.

The main function of this reward circuit is to promote behaviours necessary for survival: drinking, eating, reproduction, etc. For example, when a person feels hunger, eating releases dopamine and gives the brain a feeling of pleasure and reward. The pleasure derived from these activities drives a person to repeat the activity, therefore ensuring survival.

These vital functions are not the only activities that cause us to secrete dopamine. For example, it can be secreted when listening to music, playing sports or doing any of the activities mentioned above (gambling, compulsive shopping, etc.).

When the reward circuit is functioning normally, it contributes to mental well-being.

What is a neurotransmitter?

A neurotransmitter is a chemical molecule in the brain that transmits messages from one neuron to another. Neurotransmitters have several functions: some can change a person’s mood, some can affect concentration or memory, and some can affect a person’s experience of pain.

The effect of psychoactive substances on the reward circuit

Using substances stimulates the production of dopamine in high quantities, creating feelings of intense and immediate pleasure. The user’s memory then records the link between taking the drug and feeling pleasure (the rush). Because this intense pleasure is temporary, once a person comes off the “high,” a feeling of lack can set in. The pleasure caused by the surge of dopamine, followed by a decrease in this neurotransmitter, can drive a person to consume again in order to feel the same level of pleasure.

Tolerance and dose escalation

When a person regularly uses certain substances, they may develop a tolerance: the feeling of pleasure provided by the substance becomes less and less intense. The person must therefore increase the dose to achieve the level of pleasure provided by the initial doses.

This phenomenon of tolerance plays an important role in the transition to problematic use, whereby the substance occupies an increasingly central place a person’s life, often to the detriment of their health and social life. In the most severe cases, the substance may become the addicted person’s sole focus. They then spend most of their time and money acquiring and administering the substance, repeating the cycle.

Note: not all substances lead to tolerance. This is the case with amphetamines, for example. However, it is possible to become addicted to a substance without developing tolerance.

Tolerance is also a factor in behavioural addictions, including gambling. A person may feel driven to devote more and more time to gambling in order to maintain a certain level of pleasure, to the detriment of their social life and financial health.

Psychological addiction, physical addiction and withdrawal

There are two types of addiction: physical addiction and psychological addiction. These two forms of addiction are very different from each other.

Physical addiction

Physical addiction occurs when the body has become so accustomed to a substance that it requires it to function. When an addicted person stops using the substance, they experience cravings and symptoms: this is known as withdrawal.

Depending on the nature of the substance, withdrawal symptoms can vary in intensity, and may include headaches, trembling, nausea, etc. Withdrawal from certain substances, including opiates, can cause pain to the point that withdrawal becomes intolerable and requires medical assistance.

Psychological addiction

Psychological addiction stems from the effects of a substance or behaviour and the context surrounding it. It is influenced by a number of factors, including a person’s personality, lifestyle and social circle. In addition to being physically addicted, a person can also be triggered by the memory of the pleasure provided by a substance or activity. Psychological addiction lasts much longer than physical addition and can even last a lifetime.

For example, when a person smokes tobacco, nicotine quickly becomes physically addictive. After quitting smoking, this physical addiction will disappear after several days. On the other hand, psychological addiction will last longer because it is tied to habits that involve the ritual of smoking, such as coffee breaks or having a cigarette at the end of a meal. These memories continue to drive a person’s desire for cigarettes, even if they no longer suffer from any physical addiction.

We can help you

Many social, environmental or even genetic factors can contribute to the development of addiction. Each situation is unique and requires a personalized diagnosis and support from a professional who is part of the Quebec public system of addiction services. If you are concerned about your behaviour or that of someone close to you, you don’t have to face it alone: call us at 1-800-265-2626 or use the chat feature at the bottom of our site, on the right. We will refer you to an appropriate resource within our system and provide you with support. Our services are free, confidential and available 24 hours a day, 7 days a week.


Sources: Diagnostic and Statistical Manual of Mental Disorders (DSM-5) / World Health Organization (WHO) / Fédération pour la recherche sur le cerveau / McGill University / University of Alberta / Hôpital Montfort / Government of Canada / Association québécoise des parents et amis de la personne atteinte de maladie mentale (AQPAMM)