Symptoms of Substance Use Disorders

Individuals usually progress from experimentation to occasional use and then to heavy use and sometimes to a substance use disorder.

This progression is complex and only partially understood.

The process depends on interactions between the drug, user, and setting.


Drugs in the ten (10) classes vary in how likely they are to cause a substance use disorder. The likelihood is termed addiction liability.

Addiction liability depends upon a combination of factors including:

  • How the drug is used;
  • How strongly the drug stimulates the brain’s reward pathway;
  • How quickly the drug works; and
  • The drug’s ability to induce tolerance and/or symptoms of withdrawal.

In addition, substances that are legally and/or readily available, such as alcohol and tobacco, are more likely to be used first.

As individuals continue to use a substance, they often see less risk in using it and may begin to increase their use and/or experiment with other substances. An individual’s perception of risk also may be influenced by the social and legal consequences of use.

During treatment of medical illness or following surgical or dental procedures, individuals are routinely prescribed opioids. If the individuals does not take the whole amount prescribed, the drugs sometimes end up in the hands of people who wish to use them recreationally.

Because the use of these drugs for non-medical purposes has become such a large problem, many health care providers have responded by:

  • Prescribing lower amounts of opioid drugs;
  • Encouraging individuals to safely store or dispose of any leftover drugs; and
  • Expanding prescription take-back programmes.


Factors in users that may predispose to a substance use disorder include:

  • Physical characteristics;
  • Personal characteristics; and
  • Circumstances and disorders.

Physical characteristics likely include genetic factors, although researchers have yet to find more than a few biochemical and/or metabolic differences between people who develop a substance use disorder and those who do not.

Individuals with low levels of self-control (impulsivity) or high levels of risk-taking and novelty-seeking behaviours may have an increased risk of developing a substance use disorder. However, there is little scientific evidence to support the concept of the addictive personality that has been described by some behavioural scientists.

A number of circumstances and coexisting disorders appear to increase the risk of a substance use disorder. For example, individuals:

  • Who are sad, emotionally distressed, or socially alienated may find temporary relief from drug use, which can lead to increased use and sometimes to a substance use disorder.
  • With other, unrelated mental disorders such as anxiety or depression are at increased risk of developing a substance use disorder.
    • Medical professionals use the term “dual diagnosis” to refer to individuals who have both a mental disorder and a substance use disorder.
  • With chronic pain often require opioid drugs for relief.
    • Some of these individuals later develop a substance use disorder.

However, in many of these individuals, non-opioid drugs and other treatments do not adequately relieve pain and suffering.


Cultural and social factors are very important in initiating and maintaining (or relapsing to) substance use.

Watching family members – for example parents and/or older siblings – and peers using substances increases the risk that individuals will begin using substances.

Peers are a particularly powerful influence among adolescents. Individuals who are trying to stop using a substance find it much more difficult if they are around others who also use that substance.

Medical professionals may inadvertently contribute to harmful use of psychoactive drugs by over-zealously prescribing them to relieve stress.

Many social factors, including mass media, contribute to individuals’ expectation that drugs should be used to relieve all distress.