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Substance Use Disorder

While they're interrelated,  substance use, substance dependence, and having a diagnosis of a Substance Use Disorder (SUD) are very different. 

Some people you talk to will use these terms interchangeably, but they are not the same things.

And those differences and distinctions are important. 

If you're going to speak credibly about substance use, you need to understand these differences.
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 Most of us are substance users. 

We drink coffee, take medications, or use other substances to boost our energy, stay healthy, or relax and unwind.

 Anyone can become substance dependent. 

Given enough time or the right amounts of certain substances like opioids, anyone will become tolerant and dependent. Even fetuses and babies.

 Some of us will develop a Substance Use Disorder (SUD). 

Some of us will develop unhealthy patterns of use and behaviors that can have damaging health and personal consequence. Many won't. Most of us who identify as people who use drugs (PWUD) will have patterns of use that change over time and involve more than one substance. It's normal to have periods of use - and periods of abstinence.

Tolerance + Dependence
Important:  Neonatal Opioid Withdrawal (NOW), also known as Neonatal Abstinence Syndrome (NAS), is a temporary and treatable condition.
Babies are not "born addicted." 
Addiction is a set of behaviors - like "drug seeking" or "mismanaging responsibilities" - that babies are not capable of doing.

Substance tolerance and dependence are expected physiological responses that occur with prolonged exposure to certain substances.


Tolerance is when the body becomes accustomed to the presence of a substance and requires higher doses to achieve the same effect.


Dependence is when the body displays signs and symptoms of withdrawal when the substance is absent (1,2).

EXAMPLE:  If baby has been exposed to substances in the womb that creates tolerance, they may show signs of substance dependence when they're born. This is because their body has become accustomed to working with that substance in their system. When that substance is no longer there, their body needs to make adjustments. Not all substances create this dependence. And not every baby that is exposed to substances - typically in the last days and weeks of pregnancy - will show signs of exposure or withdrawal. 

What is a Substance Use Disorder?

Substance use disorder (SUD) is a mental health diagnosis.

Although Substance Use Disorder can be understood as a medical condition that is based in genetics, chemistry, and biology - it is a diagnosis that is based on seeing certain behaviors

In other words, there is no blood test or urine test for diagnosing Substance Use Disorder. While a drug test can tell you whether or not the metabolites of certain substances are present in someone's bodily fluids it can't tell you whether someone is using safely, is physiologically dependent, or is using chaotically.

SUD is diagnosed based on 11 criteria:

  1.   Taking the substance in larger amounts or for longer than you meant to

  2.   Wanting to cut down or stop using the substance but not managing to

  3.   Spending a lot of time getting, using, or recovering from use of the substance

  4.   Cravings and urges to use the substance

  5.   Not managing to do what you should at work, home or school, because of substance use

  6.   Continuing to use, even when it causes problems in relationships

  7.   Giving up important social, occupational or recreational activities because of substance use

  8.   Using substances again and again, even when it puts you in danger

  9.   Continuing to use, even when the you know you have a physical or psychological problem that could have been caused or made worse by the substance

  10.   Needing more of the substance to get the effect you want (tolerance)

  11.   Development of withdrawal symptoms, which can be relieved by taking more of the substance.


Disorders are categorized from mild to severe depending on how many of the criteria are applicable (3).

Substance use disorder (SUD) is recognized in DSM-V as a chronic, treatable condition related to use of alcohol, cannabis, hallucinogens, inhalants, opioids, sedatives, hypnotics, anxiolytics, stimulants, tobacco, and other substances (3).


Recovery is complex, defined by the individual, and is not linear. For most people, the recovery process includes one or more relapses (4).  

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Diagnosing a
substance use disorder
requires asking questions
and having conversations. 
Understanding Substance Use Disorders

Much of the research information available on illicit substances was performed with male subjects.

The bodies of women and other people who can become pregnant process drugs differently and these people can have different problems and clinical needs associated with their use.

All non-medical substance use in pregnancy is potentially problematic, and cannot be  recommended.


A Harm Reduction approach acknowledges that substance use in pregnancy does occur - and patients and providers should have the best evidence available when they create individualized treatment plans. 

We don't have enough information about how some substances affect pregnancy and lactation. We lack good health information for certain classes of substances, like hallucinogenics and many synthetics or "designer drugs."


There are some classes of substances that we do have some information about. The information on this site addresses:

  • alcohol

  • tobacco + nicotine

  • cannabis

  • opiates

  • benzodiazepines

  • stimulants

We will add information on other substances as it becomes available.

We also discuss polysubstance use - using more than one thing at a time.

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Problems with the Evidence

Many of the problems attributed to substance use may actually be caused by social determinants of health, or issues around acquisition and administration, not the substances themselves.


For example, many people identified by healthcare, law enforcement, and child welfare systems as affected by substance use, have also experienced poverty, trauma, and systemic oppression.


Because of this and other factors, high quality research that controls for all variables is difficult, if not impossible to find.

  1. Tolerance. (2016). In Merriam-Webster’s Medical Dictionary. Retrieved from

  2. Dependence. (2016).  In Merriam-Webster’s Medical Dictionary. Retrieved from

  3. American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.

  4. McLellan, A. T., Lewis, D. C., O'Brien, C. P., & Kleber, H. D. (2000). Drug dependence, a chronic medical illness: implications for treatment, insurance, and outcomes evaluation. JAMA, 284(13), 1689–1695.

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