Drug overdose is a major cause of death in the United States, especially in young people. In fact, it’s the leading cause of death in people under 50-years-old. According to the Centers for Disease Control and Prevention (CDC), 841,000 people have died in overdoses since 1999, and 70,630 experienced a fatal overdose in 2019. Opioids are a significant factor in the number of drug overdose deaths that happen in the U.S. each year. They killed 49,860 people in 2019. But which drugs can cause a fatal overdose, and what happens during an overdose. Learn more about drug overdose and what causes it. 

What is a Drug Overdose?

A drug overdose is an excessive dose of a drug that leads to mental or biological complications that can be unpleasant, damaging, or life-threatening. Some drugs only cause uncomfortable symptoms when they’re taken in high doses. For instance, marijuana and psychedelics aren’t known to have effects that can damage your body or lead to life-threatening complications in high doses. But they can cause uncomfortable side effects that can lead to temporary paranoia, irritability, panic, nausea, and even psychosis. 

Other drugs can leave damaging effects on the body depending on the drug’s toxicity. Toxicity is a substance’s ability to damage organs, the brain, or other parts of the body. Prescription drugs are tested for toxicity and approved if it’s low enough that moderate doses would cause serious harm. But an overdose can be toxic. For instance, alcohol can damage your liver in very high doses.

Many drugs can cause dangerous complications during an overdose through the high intensity of their effects. Stimulants and depressants speed up and slow down nervous system activity. When these drugs are taken in high doses, the drug’s activity can have dangerous effects on important functions of your nervous system. Some overdoses can be reversed with antagonists, which are drugs that counteract the effects of a substance by blocking receptors in the brain that the drug would normally activate. For instance, opioid overdose can be reversed with an opioid receptor antagonist called naloxone. But these overdose antidotes only work if they’re administered in time.

Which Drugs Can Cause a Fatal Overdose?

There is a wide variety of prescription and illicit drugs that can have some fairly severe side effects when they’re taken in high doses. Three major drug categories that span both legal and illegal drugs include depressants, stimulants, and opioids. These three make up a significant portion of drug overdose deaths in the United States. While many drugs that fall into these categories can be beneficial to people that have medical and psychological needs, they can also be misused in a way that leads to dangerous side effects and even deadly overdose. Here are some drugs that can be dangerous during an overdose and how they may affect you:


Central nervous system depressants are a class of drugs that can slow down activity in your nervous system. Depressants include alcohol and a range of prescription drugs like barbiturates, benzodiazepines, and certain sleep aids. Depressants can cause an overdose by slowing down some vital functions of your nervous system. Your brain controls some important automatic functions, including your breathing, heart rate, and blood pressure. Depressants can slow or stop all of these functions leading to coma and death. 

 Alcohol is the most common substance that’s tied to depressant overdose. Alcohol overdose, also called alcohol poisoning, can happen when you drink too much in a short time frame. As your blood-alcohol concentration (BAC) rises, you may start to experience impairment of different brain and body functions. 

With each standard drink, your BAC rises around 0.02%, depending on many factors like your age, sex, and weight. At 0.08%, you’re past the legal driving limit, and your chances of an accident increase. Between 0.08 and 0.25%, your motor skills and cognitive ability will get worse, making accidents more likely. At 0.25%, you are in significant danger from alcohol poisoning. You may lose consciousness, vomit, slip into a coma or die. Alcohol poisoning can be fatal in a number of ways. It can slow down your breathing and heart rate to a deadly degree, but it can also cause you to throw up while unconscious, which can cause you to choke or aspirate vomit. 

Barbiturates were a common prescription drug through the 20th century, but they’ve become less common with the introduction of alternatives like benzodiazepines. Still, they’re prescribed in some cases, especially to treat epilepsy or as a hypnotic drug. Barbiturates are known to cause dangerous overdoses when used in high doses, which is part of the reason they were replaced for common use. It’s possible to take a dangerous dose of some barbiturates accidentally, but they can also be very dangerous when misused. They can cause overdose symptoms like slowed or stopped breathing or a slow heart rate. 

Benzodiazepines are similar to barbiturates, but they are generally thought to be safer. Benzodiazepines may be less likely to cause life-threatening overdose symptoms when used in high doses; however, they can cause unpleasant symptoms like drowsiness, memory issues, cognitive impairment, and motor skill impairment. Taking benzodiazepines in extremely high doses does have the potential to cause a life-threatening overdose. 

Drugs like Ambien and Sonata that are used as sleep aids are in a category of drugs called non-benzodiazepine sedatives or Z-drugs. These drugs aren’t as powerful as benzos or barbiturates, and they’re less likely to cause a life-threatening overdose. A high enough dose or mixing the drug with other substances could potentially be dangerous.


Central nervous system stimulants include both illicit and prescription drugs that increase activity in your brain and nervous system. Stimulants include drugs, like cocaine and methamphetamines and prescription drugs like ADHD medications. Stimulants often work by increasing the levels of certain chemicals in your brain like dopamine, which create a powerful sense of reward, pleasure, and alertness. They can also cause some biological changes like an increase in your heart rate and blood pressure. 

Illicit stimulants can be intense when they’re taken in high doses. Meth and cocaine can cause paranoia, shaking, tremors, agitation, panic, and seizures. High doses of powerful stimulants can also cause something called stimulant psychosis, which is characterized by hallucinations and delusions. Psychosis that’s caused by stimulants usually goes away when the drug wears off. 

Cocaine and meth often have short-lived but potent highs followed by an uncomfortable comedown. Because of this, the drugs encourage repeated use and binging to keep up the positive feelings and stave off uncomfortable side effects. Binging can increase your chance of experiencing serious side effects like psychosis and overdose. A stimulant overdose can cause your heart rate and blood pressure to increase to the point of causing chest pains, irregular heartbeats, heart failure, difficulty breathing, and stroke. 

Amphetamines that are used in ADHD medications are stimulants, but they aren’t as potent as illicit stimulants like cocaine. They aren’t known to cause fatal accidental overdoses, but they may be dangerous or uncomfortable in high doses. They may also be dangerous in high doses to people with heart conditions. 


Opioids are a class of drugs that are used as prescription painkillers. Opioids include prescription-strength substances like oxycodone, hydrocodone, morphine, and others. It also includes drugs that are illegal in the United States, like heroin. Opiates occur naturally, and they were first found in opium poppy plants and were later found in the human body in the form of endorphins. The substances that were found in those plants (codeine and morphine) were later altered to make new opioids like heroin and oxycodone. Scientists have also created completely synthetic opioids like fentanyl, which are extremely powerful. 

Opioids bind to your body’s opioid receptors, but they’re able to relieve pain better than your native endorphins, which is why they’re effective in treating moderate to severe pain symptoms. They block pain at opioid receptors in muscle tissue, organs, bones, the spine, and the brain, making them extremely effective. However, they also slow down some nervous system activity, similarly to depressants. In high doses, opioids can slow down your breathing to the point of oxygen deprivation, coma, and death. An opioid overdose is much more likely when the drug is abused, especially when it comes from illicit sources. Heroin and counterfeit opioid pills are often mixed with fentanyl, which is 100 times more powerful than morphine and can be fatal in a dose as small as 2 milligrams. c

Overdose and Suicide

Overdose often happens as an accident, but it’s sometimes done intentionally. According to the National Institute of Health, people who visit emergency departments for opioid overdoses are 15 times more likely to die by suicide when compared to the general population. Not only is overdose a suicide method, but suicide and substance use disorders are often connected. Around half of the people with substance use issues also have other mental health problems like depression. However, suicidal thoughts and actions are often the results of underlying issues that can be treated, even if they feel like they will last forever. If you experience these feelings, it’s important to speak to someone as soon as possible. Talking to a professional or seeking treatment may be a step toward feeling better.

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