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3 different stages of substance abuse – Tolerance, dependence and addiction

3 different stages of substance abuse - Tolerance, dependence and addiction

For many people, tolerance, dependence and addiction mean the same, and they use these terms interchangeably. However, each term has a different meaning, which is based on a substance’s effect on the user’s body and brain.

Let us understand these terms in detail.


The National Institute on Drug Abuse (NIDA), defines tolerance as “a state in which the person no longer responds to a substance in the way that person initially responded.” Tolerance is a result of repeated use of drugs over a long period. It increases the user’s need of higher amounts of a substance to achieve the same effect, which the person used to achieve with comparatively lower doses previously or at the onset of use. This is the reason people with substance use disorders continue using more and more to get a “high.”

In the case of drugs like morphine and heroin, tolerance is an outcome of analgesic effects of the drugs. Though tolerance is largely independent of addiction, there are many drugs with both tolerance and addiction potential. The brain areas involved in the development of tolerance to the soothing effects of morphine are different from those involved in the reward pathway. The two areas — thalamus and spinal cord — send pain messages and produce the desired effect.


Dependence is a state when an individual is able to function normally only under the influence of the substance. Dependence is associated with the appearance of withdrawal symptoms in the case of drug abstinence. Withdrawal symptoms are characterized by a group of physical, mental and emotional changes, which may range from being mild to life-threatening.

While mild symptoms may be triggered by abstinence from stimulants like caffeine, alcohol or opioids, including heroin and prescription pain relievers, may produce fatal consequences. People using a prescription medicine daily for a longer duration are vulnerable to developing a dependence to the drug. However, drug dependence may not necessarily lead to addiction. The brain regions involved in developing dependence include the thalamus and the brainstem, and like tolerance the mechanism is different from the reward pathway. However, if one is addicted, they are likely to be dependent too.


As opposed to tolerance and dependence, addiction is a serious health problem. People addicted to a certain substance cannot resist the urge to take the drug. In fact, the urge is so strong that it becomes uncontrollable, despite knowing that the drug is harming them. When people start taking a substance they are ignorant of the fact that they can become addicted to it. They simply enjoy the euphoric feelings and tranquilizing effects of the substance. They are under the impression that they can quit when they want. However, the continuous use alters the brain in a way that it increases the craving even when the user may not have the need. It happens so quickly that users fail to realize when they got addicted.

Addiction also leads to a plethora of other problems like sleeping and eating disorders, increased blood pressure, anxiety, depression, risk of heart attack and suicidal ideation. The thought of getting and using the drug engulfs every moment of a person’s life and strips him or her of the pleasures of life. A person addicted to a substance of choice may do anything including lying, stealing or hurting people to meet his or her drug needs.

Dealing with addiction

Addiction is a serious disease like cancer and diabetes, which needs proper treatment. Due to the stigma associated with mental illnesses and substance use, as well as lack of health care facilities, treatment is delayed and chances of recovery and living a sober life are reduced. Those addicted to any substance are advised to seek an expert’s help in leading a healthier and productive life.

The Texas Substance Abuse Helpline is a useful online resource that provides valuable information about substance abuse including treatment alternatives and substance abuse treatment centers in Texas. You can chat online or call our 24/7 helpline number 866-971-2658 to find out the best substance abuse treatment programs in Texas.