illustration - woman standing on brain in water surrounded by sharks - toleranceIt’s not always easy to tell if someone is struggling with a substance use disorder. Since the condition is classified as a chronic and progressive illness, someone can appear to be quite functional to the casual observer yet still have significant problems related to their drug or alcohol use.

Understanding Terms

If you are worried about a loved one’s recent substance use, understanding the difference between tolerance, dependence, and addiction is a crucial step in determining whether treatment is necessary. These terms are closely related but not interchangeable.


Tolerance is the process of the body gradually adapting to a substance. Over time, when a person uses a substance regularly, they will develop a tolerance and need a higher dose to experience the same effects.

Tolerance can be a warning sign that someone has an addiction, but tolerance isn’t necessarily problematic in itself. For example, a wide range of prescription medications can lead to tolerance, even when they are being used exactly as prescribed under a doctor’s supervision for a legitimate medical condition. When medications known to lead to tolerance are prescribed, patients require close supervision to ensure the medication continues to work effectively and that an addiction doesn’t develop.

People who drink alcohol regularly can also develop a tolerance. This can be a warning sign that someone has a drinking problem, but tolerance is also affected by factors such as height, weight, muscle mass, hormone levels, and ethnicity. For example, men generally have more of a tolerance to alcohol than women even when they drink at the same levels because they tend to be taller, heavier, and more muscular.


Dependence means that a person’s brain only functions normally when a substance is present in the body. When substance use is discontinued, the person experiences withdrawal symptoms. These symptoms often include signs of physical discomfort, such as sweating, headache, upset stomach, or heart palpitations. Mood changes, such as fatigue, depression, or anxiety, are also common.

People who have a history of substance abuse are more likely to experience dependence, but it’s still possible to become dependent on a substance with no known risk factors. For example, many prescription medications carry a high risk of dependence—including antidepressants, anti-anxiety medications, and painkillers. When a patient is taking these medications, they need to be slowly weaned off the medication to avoid problematic withdrawal symptoms.

Dependence, like tolerance, is a warning sign of addiction. However, it does not mean that someone is addicted to a substance. For example, a patient taking the antidepressant Paxil who experiences withdrawal symptoms such as dizziness, fatigue, and headaches, is not addicted to the medication. Since they’re not using the medication to get high, their brain just needs time to rebalance. This is why tapering of doses is recommended for most patients who are discontinuing antidepressant medications.

In most cases, withdrawal symptoms are merely uncomfortable and not physically dangerous. However, people who are long-term abusers of alcohol, opioids, or benzos can experience dangerous seizures, cardiac complications, or thoughts of self-harm. For this reason, medically-managed detox is a necessary part of addiction treatment.


Although tolerance and dependence are warning signs of addiction, it’s possible for someone to become addicted to a substance without experiencing either. For example, someone who is using marijuana to self-medicate anxiety may become mentally dependent without experiencing physical tolerance or the withdrawal symptoms that indicate a physical dependence.

Some other warning signs that suggest someone has an addiction include:

  • Declining performance at work or school
  • Lack of interest in activities that one previously enjoyed
  • Declining personal hygiene
  • Change in sleeping habits
  • Dramatic changes in mood and behavior
  • Lying or becoming angry when friends or family ask about substance abuse
  • Stealing or engaging in reckless financial behavior to fund an addiction
  • Having unsafe sex or engaging in other types of risky behavior while under the influence

Getting Treatment

Addiction, more often referred to in the medical community as a substance use disorder, is a chronic illness with complex biological and environmental triggers. It is not a character defect or something that can be cured with willpower alone.

If someone has a substance use disorder, they need access to evidence-based care that is personalized to fit their own unique needs. No two people with addiction are exactly alike. Past experiences of trauma, co-occurring mental illnesses, and the presence of other serious medical conditions such as diabetes or high blood pressure can all impact a person’s recommended care plan. Previous relapse is another important factor to consider, as this suggests that past treatment attempts failed to correctly assess individual needs.

At St. Joseph Institute for Addiction, we provide a full continuum of care for men and women with substance use disorders. Our residential drug and alcohol addiction treatment combines detox, individual counseling, recovery education, relapse prevention, and continuing care to help clients build the foundation for lasting sobriety.

To learn more about SJI addiction and mental health treatment in PA, and our programs, please contact us at (888) 352-3297.