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Why Drugs Are Addictive? – The 10 Hardest Drugs To Kick

Dr. Gerardo Sison

Medically reviewed by

Dr. Gerardo Sison

April 1, 2019

When an individual consumes drugs or alcohol it activates the reward center in the brain and gives a person a feeling of pleasure or euphoria. This feeling of reward and euphoria is what makes drugs and alcohol so addictive and difficult to quit.

The human brain and central nervous system is an intricate and highly evolved system that has directed our species toward the foods and activities that promote and sustain life for hundreds of thousands of years. When primitive humans located a food source that was good for them, their brain captured a snapshot of their surroundings, storing patterns to make locating that food source more efficient in the future.

At the same time, a part of their brain known as the nucleus accumbens, also known as the pleasure center of the brain, released the neurotransmitter dopamine, leaving early man feeling a bit euphoric over these good food sources, and generating food cravings specific to these recognizable patterns found in their native environment.

It’s a near-perfect system: human finds food, the location of the food source is cataloged in the brain, human is rewarded for finding food, cravings are initiated when similar patterns are seen in an environment, food source is more easily located, and the cycle repeats.

This same mechanism built on smaller feedback loops, designed to keep us healthy and thriving, is also our Achilles heel when it comes to addictive substances. The hardest drugs to kick trigger the same highly evolved reward mechanism at a magnitude hundreds of times more powerful than anything occurring naturally. Drugs and alcohol hijack our reward centers, rewire its intricate circuitry, and disengage the decision-making parts of our brain, leaving us vulnerable to the ill-effects of the substance.

Another factor in drug or alcohol dependency is the dose and duration of use. When someone abuses a substance, it alters the release of key neurotransmitters and hormones, elevating them beyond what would ever occur naturally. The brain, in its quest for homeostasis, attempts to regulate these spikes by increasing or decreasing receptor sites for these neurotransmitters as needed to reduce the extreme fluctuations caused by drugs or alcohol.

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Have you ever wondered why you get a headache and feel groggy if you don’t get that first sip of coffee straight away in the morning? Caffeine, a highly addictive substance, binds with the same receptors normally occupied by the nucleoside adenosine. Adenosine naturally accumulates during the day, triggering periods of rest for the body. In other words, it makes us feels sleepy when our bodies need to rest. Someone using caffeine temporarily blocks this process, leaving them feeling alert for a period of time.

The brain responds to this change by increasing the number of receptor sites for adenosine, which is felt by the caffeine-addicted person as one cup of coffee turns into two cups for a similar effect. When that person then tries to quit caffeine, they are met with a flood of adenosine and the multitude of now-available receptor sites previously tied up by the caffeine. This process makes quitting caffeine or other addictive substances, to a greater or lesser degree, challenging.

Top 10 Most Addictive Drugs

Heroin is a powerful opioid analgesic made from the naturally occurring resin found on opium poppies. A recent drug survey indicated more than half a million people admitted to using heroin in the past year. It is considered one of the hardest drugs to kick, by measure of how quickly dependence is developed. Quitting heroin delivers a punch in the form of serious withdrawal symptoms, including severe agitation, insomnia, muscle and bone pain, gastrointestinal upset, paranoia, depression, anxiety, and involuntary muscle movement. [Learn More]

While methadone is an opioid agonist used as a treatment for heroin addiction, it is an equally addictive substance. While it does not induce the same euphoria, and individuals can use the substance to become functional again off of heroin, quitting methadone is similar to quitting heroin and can induce vomiting and diarrhea, flu-like fever and chills, aching bones and joints, heightened pain sensitivity, depression, anxiety, fatigue, hallucinations, and extreme paranoia. [Learn More]

Amphetamines are strong central nervous system (CNS) stimulants used in the treatment of attention deficit hyperactivity disorder (ADHD), obesity, and historically during wartime to increase focus and reduce troop fatigue, and even as an antidepressant. Amphetamines increase levels of the excitatory neurotransmitters norepinephrine and dopamine, resulting in a feeling of hyper concentration and, In individuals who abuse amphetamines, feelings of euphoria. As a person continues to abuse amphetamines at higher than the prescribed dosage, their natural ability to elevate levels of dopamine and norepinephrine are reduced, and severe fatigue related to this decrease, along with other significant symptoms, are experienced upon withdrawal from the drug.

As with any highly addictive substance, for someone dependent on the drug for focus, this can perpetuate a need for the drug for feeling any semblance of normal. [Learn More]

Crystal Meth / Methamphetamine
Methamphetamine is far more potent amphetamine drug that is widely abused for its longer lasting effects. Like amphetamines, methamphetamines increase central nervous system activity by increasing levels of norepinephrine and dopamine. They also increase levels of serotonin, a neurotransmitter related to mood, cardiovascular function, sleep, appetite, among other important functions. With these three neurotransmitters elevated, the brain begins reducing the number of receptor sites, leading to severe withdrawal symptoms including extreme fatigue, unstable mood or agitation, paranoia and anxiety, severe depression, and increased appetite. [Learn More]

Crack Cocaine
Crack cocaine is a far more potent form of cocaine, upwards of 75-100 percent pure cocaine. Crack cocaine is considered the poor man’s cocaine, inexpensive to start, though once addicted, a habit can quickly become costly.

A person with high risk factors toward addiction may become quickly dependent on cocaine after only a few exposures to the substance. The primary mechanism for the addiction is the unusually high dopamine response, resulting in euphoria lasting just 10-15 minutes. The short duration of the high perpetuates continued use or “binging” on the drug, resulting in a biochemical disturbance the brain responds to by shutting down dopamine receptors. This biological response leads to some significant withdrawals including severe depression, anxiety, paranoia, agitation, fatigue, and violent mood changes. [Learn More]

Cocaine is a central nervous system stimulant made from the the leaves of a coca bush. It works on the same dopamine response as crack cocaine, though in a less potent form. Both crack cocaine and cocaine stimulate the central nervous system and elevate dopamine, and reducing intake of the substance leads to similar withdrawals. [Learn More]

Pentobarbital is a dangerous drug. It’s a barbiturate used in lethal execution and overdose deaths are often linked to increased tolerance to the substance. To complicate matters, withdrawals from this potent barbiturate can also result in serious conditions including delirium and seizures.

Pentobarbital increases levels of gamma aminobutyric acid (GABA), an inhibitory neurotransmitter, relaxing muscles, lowering blood pressure, and is involved in regulating sleep schedules and reducing anxiety.

The longer a person is abusing barbiturates like pentobarbital, the more time for changes to occur within the brain and along the CNS resulting in a reduction in the number of GABA receptors. Withdrawals reflect this reduction in GABA and include severe anxiety, involuntary muscle spasms and rigidity, hallucinations, insomnia, and gastrointestinal upset. [Learn More]

Benzodiazepines replaced the more dangerous barbiturates in medicine to treat anxiety disorder and conditions including insomnia. However, despite being safer, benzodiazepines increase dopamine levels, and when abused at higher than prescribed doses, pose a serious addiction risk. They also result in increases in GABA transmission. Increases in both neurotransmitters can result in decreases in related receptor sites and a physical dependence on the drug. Withdrawals from benzodiazepines include heightened anxiety, paranoia, depression, mood changes, trouble focusing, and gastrointestinal upset. [Learn More]

Despite the known health risks associated with nicotine, it is widely and legally available, and regularly overlooked as a highly addictive substance. Nicotine acts on the reward centers of the brain just like other drugs, resulting in increased levels of dopamine over anything that would occur naturally. Nicotine is hard to quit because as the body adjusts to the intake of the substance, it decreases dopamine receptors, resulting in mood changes that include apathy, depression, anxiety, and extreme cravings for more nicotine.

According to the Centers for Disease Control and Prevention (CDC), on average, one in 10 working adults dies from excessive alcohol consumption. While certain genetic and environmental factors can increase someone’s susceptibility to addiction, alcohol is widely available, affordable, and its widespread use is socially accepted and even promoted, making it one of the most commonly abused substances worldwide. Alcohol’s long-term effects on the body include brain shrinkage, cancers, and liver disease.

Alcohol, like all highly addictive substances elevates increases dopamine release along the reward pathways in the brain. Repeated exposure to the drug leads to tolerance for the alcohol. Alcohol withdrawals from long-term alcohol abuse may be life-threatening and must be medically managed. Withdrawal complications from alcohol may include serious depression, anxiety, convulsions, delirium, and even death. [Learn More]

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