Drugs fascinate human beings. For thousands of years we have sought chemicals to change our minds. From alcohol to opium to peyote, drugs have been both coveted and hated for their effects on humans. This article’s intent is to summarize different kinds of drugs and how they affect the brain.
A drug is any synthetic or natural substance that, once introduced into the body, will temporarily alter normal functioning in the brain and or body.  By that definition caffeine, tobacco, alcohol, aspirin, prescription medication, and other common everyday substances are drugs just like heroin, cocaine, ecstasy, and marijuana. The difference is in the legality and severity of these substances on the brain. Some drugs are illegal and/or carefully controlled by law, such as heroin. Heroin as a street drug is strictly prohibited by law but Oxycontin, which is a pharmaceutical created synthetic heroin, is legal with a prescription.
Some of the most famous drugs of all are psychoactive, which alter perception, consciousness, and behavior by acting primarily on the central nervous system and brain.
The blood-brain barrier (BBB) is a thin membrane that acts as protection for the brain. This barrier evolved over many millions of years to keep our most important organ, the brain, safe from any harmful chemicals that might enter the body. A network of endothelial cells scrunched closely together, the BBB allows necessary molecules like water, oxygen, and carbon dioxide to pass in and out but will keep anything heavier than 500 daltons from entering, unless it is taken in by specialized transport systems.  This keeps viruses, bacteria, and around 98% of drugs from being able to infiltrate the central nervous system and brain. It also keeps immunoglobulin proteins, which are part of our immune system, from being able to get into the brain to fight off any harmful invaders. The BBB is so limiting in what it accepts that scientists are faced with the problem of developing drugs that can help the brain and central nervous system.
One promising technique is to hijack the transportation molecules that are used by the body to allow specific large molecules to pass the BBB. The drugs could be sent attached to these molecules and the BBB would accept it, figuring that it is something like Glucose, which is too big for the BBB but is constantly allowed because of its importance.
Nanotechnology might also help to send large drug molecules through the BBB.  Still being researched, this involves attaching a nanoparticle to a drug which then somehow stimulates the BBB and allows the molecule through.
Eating food, having sex, and drinking liquid are all examples of things humans do to feel good. We have evolved to seek pleasure as a means of survival. Without this drive we would not have any desire to mate or feed ourselves.
When we do something pleasurable, the feelings we get are influenced by a network of neurons called the reward pathway.  The purpose of this network is to reinforce action that is necessary for our survival, such as eating. Not all actions that stimulate the reward pathway are positive, however, as it can be activated by doing things that aren’t necessarily healthy or beneficiary. The reward pathway is also called the mesolimbic pathway and was discovered in 1954 by James Olds and Peter Milner.
The mesolimbic pathway connects the ventral tegmental area (VTA), located in the central midbrain, to the nucleus accumbens and prefrontal cortex.  When bodily needs are being satisfied, signals are sent to the VTA which cause the VTA to produce dopamine. The dopamine is sent along the mesolimbic pathway to the nucleus accumbens. The nucleus accumbens is part of the limbic system and is crucial to the sensations that accompany pleasurable activity. Lastly, the nucleus accumbens will send messages to the prefrontal cortex. The prefrontal cortex, which is in charge of planning and reasoning, will take the pleasure messages and write them as memories. These memories cause us to seek the pleasure again, and the action is reinforced.
Drugs can cause addiction by elevating the amount of dopamine in the nucleus accumbens. Dopamine is a chemical that gives us feelings of pleasure, and we develop the desire to feel this pleasure. Some drugs flood the brain with so much dopamine that the brain isn’t sure how to respond to these unnatural levels. Over time the brain will change it’s neurons to have less dopamine receptors and therefore less excitability. This decrease in dopamine receptors causes us to seek a larger amount of the drug to feel the same high we once did. This is also called building a tolerance. In the absence of the drug the person will feel lousy as their dopamine levels come crashing down to the normal level. Since there are fewer dopamine receptors, this normal amount of dopamine does not suffice. People who have become addicted to a drug will constantly require it to feel good. As their tolerance increases, the quantity required to feel good gets higher.  The process of getting and consuming drugs can take over people’s lives. If they can’t get their hands on the drug anymore then they will go into a period of withdrawal. Withdrawal leaves the person with intense cravings for the drug and it can be so powerful that they do things or act in ways they normally would not. Those in withdrawal will also experience anhedonia which is the inability to experience pleasure in situations that most humans would find pleasurable.
The human brain has two neurotransmitters that control how fast or how slow neurons are fired. Glutamate binds to NMDA, which causes neurons to become excited and more likely to fire. GABA causes neurons to slow down and become less likely to fire. Without the presence of drugs our brains usually regulate glutamate and GABA levels to provide a natural balance and neuron speed. Depressants are drugs that will throw off this balance and result in the brain being slowed down.
Ethanol is the primary drug in all alcoholic beverages. It is a legal drug that is often used in social functions. It is usually made through the fermentation of fruits, grains, and plants. Extremely popular, alcohol can be purchased over the counter in supermarkets, liquor stores, bars, and restaurants. Alcohol is ingrained into popular and ancestral culture. In the early 20th century alcohol was prohibited in certain parts of the world. In the United States, prohibition of alcohol took place from 1920 to 1933 after the passing of the 18th amendment.  It failed miserably, causing many people to rebel against the law and drink in illegal taverns that had sprung up across America during this time. These underground establishments also bred organized crime. In 1933 the government repealed the 18th amendment.
Ethanol is a globally acting molecule that decreases the activity of NMDA receptors and increases the activity of GABA. Both of these reactions slow down the brain’s neurons. Alcohol also increases endorphins and dopamine which is what makes it feel good and is the main reason people enjoy drinking. When someone becomes drunk or highly intoxicated by Alcohol, their brain will be so affected that they lose balance, slur, have no inhibition or higher level thinking capabilities, and sometimes even become unconscious or die. While drunk it is difficult to control the body or think clearly, which is why it is illegal to drive or operate heavy machinery while intoxicated.
People who drink large quantities of alcohol often find their memory impaired. They sometimes can’t recall anything that happened while they were drunk. Since alcohol damages the areas of the brain responsible for creating new memories, people who are dependent on and abuse alcohol can develop dementia, or the inability to remember things.  Dendrites, which are the branches on a nerve cell, are permanentely damaged and or changed by the use of alcohol.
Those who drink alcohol on a day to day basis or binge drink do great damage to their health. To the human body, ethanol is a poison. It can damage the heart and cause cirrhosis of the liver. After heavy drinking people often experience hangovers, which are periods of intense discomfort as the body works to cleanse itself of ethanol and restore proper mental and biological functioning. Alcohol causes deficiencies in vitamin K and other nutrients. Its disruption on the body’s ability to digest foods can cause malnourishment. It is law in many countries to post warning labels on any alcoholic beverages being commercially sold. A common warning label in the U.S. warns pregnant women about the negative effects drinking can have on their unborn child.
Alcohol withdrawal can leave addicts with jitters, sweats, headaches, and sometimes hallucinations and convulsions. A small percentage of alcoholics withdrawing from ethanol will experience alcohol withdrawal delerium, or delerium tremens. Sufferers will have powerful delusions. Ten percent of alcoholics will die while going through alcohol withdrawal delerium. 
There are some studies which show that alcohol, many times being red wine, can provide some health benefits when consumed in moderation. These benefits are a lower risk of heart attack, alzheimers, stroke, and diabetes.  None of these benefits are 100% proven to be fact, whereas the negatives to alcohol have consistently been proven through the number of related deaths every year. Binge drinking, especially on college campuses, results in a significantly alarming number of deaths per year. It is probably safest to avoid alcohol as much as possible.
Barbiturates were first discovered by Adolf von Baeyer in 1864. Baeyer synthesized barbituric acid by condensing urea with ester, and discovered that the acid had a calming effect once ingested. At higher doses it was capable of taking away consciousness. This gave barbiturates a number of medical uses including sedation and anesthesia. They have been used as anticonvulsants and sleep aids as well. Two famous medicines in the barbiturate family are pentobarbital and phenobarbital. There are serious health risks that accompany barbiturates, so they are now only used mostly in hospital settings as an anesthetic.
Barbiturates target GABA receptors in the brain, which decreases the likeliness of neuron firing. They also block sodium channels which can slow down neurons as well. The problem with using barbiturates as sedatives is that it is hard to calculate a dose that will relax someone rather than put them in a coma. There have been a couple of famous deaths that had to do with misuse or accidental overdose of barbiturates; Marilyn Monroe and Jimmy Hendrix.  Barbiturates also cause physical and psychological dependency. Users build up tolerance levels and desire more and more of the drug as time goes on. For all these reasons, barbiturates have been phased out as a typically described family of medication. Currently only about 20% of all depressant medications are for barbiturates.  There are still people who abuse and or sell these drugs illegally.
When barbiturates began to be phased out of typical depressant prescription, benzodiazepines took their place. They are much less dangerous than barbiturates when it comes to overdosing. The first benzodiazepine, later called Librium, was discovered in 1954 and then marketed and sold in 1960. From Librium there have been many descendents in the benzodiazepine family, among them Valium and Xanax. They are a lot like barbiturates in that they bind to GABA receptors in the brain and cause sedation as neurons fire less often. They have been used to help treat insomnia, convulsions, agitation, anxiety, and alcohol withdrawal. 
There are some potential negatives to benzodiazepines, the biggest being its ability to cause physical dependence. Because it psychologically changes the level of activity in the brain, those taking benzodiazepines must be weaned off to prevent anxiety, insomnia, or delusions. Benzodiazepine is a controlled substance in most parts of the world. A prescription is required to obtain any. Because they are desired by those looking for a high, dealers will illegally sell benzodiazepine and users will illegally buy them. Studies have shown that most people who use benxodiazepines will also use other, harder drugs during their lifetime. 
Whereas depressants slowed down the brain, stimulants speed it up. They affect the central nervous system in a number of ways. Stimulants can be used and abused by those looking for a high or increased mental awareness and concentration. They can also be prescribed as medication to help those who suffer from narcolepsy, ADHD, and obesity.
Caffeine is the most popular psychoactive drug in the world, with around 120,000 tons of it being globally consumed every year.  Many people are physically or psychologically addicted and use caffeine on a daily basis. Caffeine increases feelings of mental and physical awareness as well as giving feelings of euphoria or well-being. Too much caffeine can result in nervousness, heart palpatations, sweating, and sometimes delerium or vomiting. It is found naturally in coffee beans, teas, guarana, and other fruits, leaves, and plants. It is powerful enough to kill the bugs that eat it, making caffeine a naturally occuring pesticide.
A cup of coffee contains around 100 milligrams of caffeine. Tea usually has 50 milligrams. Caffeine is added to many soft drinks such as Pepsi, Coca Cola, and Mountain Dew. There is also a very big ‘energy drink’ industry, which are drinks that have varying amounts of caffeine. These drinks will usually have anywhere from 30 to 150 milligrams of caffeine.  Chocolate has very small amounts of caffeine. Caffeine can also be found in pills such as No Doz. Some of these pills are marketed toward those who work long hours or need an extra boost in concentration. Other times pills with caffeine are marketed as being able to help people lose weight.
Caffeine is absorbed into the bloodstream where it enters the central nervous system and binds to receptors on nerve cells. These receptors usually take in adenosine, which slows down neurons. Caffeine is similar in structure to adenosine, so it is able to bind to these receptors. Since the caffeine molecules are blocking adenosine, the neurons in the brain speed up. These quickly firing neurons trigger the autonomic nervous system to release noradrenaline which increases heart rate. Dopamine levels increase and the person is left very excited and energetic.
Caffeine is abused in many parts of the world. It is addictive and some people will not feel like their ‘normal’ selves unless they’ve had caffeine that day. Withdrawal from caffeine can leave a person with headaches, fatigue, and irritability. Blood pressure often decreases when caffeine is taken out of one’s diet.
Another popular psychoactive drug is Nicotine, which is found in the plant Nicotiana tabacum (Tobacco). This plants leaves are commonly dried, shredded, and then smoked in cigars, pipes, or cigarettes. Tobacco can also be chewed in the mouth. . Nicotine is highly addictive and therefore became a lucrative drug for those who grew tobacco. Around 1.3 billion people in the world smoke cigarettes and around 5.4 million people die each year from smoking related illness.  Tobacco contains over 100 different chemical compounds besides nicotine and it has been proven to be carcinogenic as well as harmful to parts of the body such as the liver and heart.
Nicotine enters the bloodstream from the lungs or skin and is immediately taken to the brain, where it will bind to nicotinic acetylcholine receptors. By fooling the brain into thinking there is acetylcholine, a neurotransmitter, then muscles will be contracted and noradrenaline is released. This improves attention and memory, suppresses appetite, and releases dopamine. Heart rate and blood pressure increase as well. All these reactions cause nicotine consumption to be habit forming. As the brain gets used to nicotine’s affects it will show plasticity and tolerance will be built as the brain changes itself to be less easy to stimulate. The longer someone smokes the more they will have to smoke a day to feel the same effects they did when they first started.
Amphetamines are powerful ‘uppers’ which increase the activity of neurons and cause them to release noradrenaline, dopamine, and serotonin. As a result, excitability, euphoria, energy, and stamina increase.  Amphetamine substances can be addictive and prolonged use causes insomnia, irritability, aggressiveness, and paranoid psychosis. Amphetamines are abused by partyers and overworkers. They are also taken by people who want to lose weight, which was what the founder of amphetamines originally thought it could be used for. Amphetamines are prescribed sometimes to those with Narcolepsy or ADHD. Common prescription amphetamines are Ritalin and Adderall.
The military is known to have used and still use amphetamines to improve the alertiveness of troops or pilots.  In World War II, troops were given Dexedrine, an amphetamine, to help them stay agile during battle. Even today, pilots who must go on long missions are sometimes given Dexedrine.
One amphetamine class drug that has gained notoriety in the last few decades is MDMA, or ecstasy. This drug is illegal in many parts of the world and causes extreme neurological and physical damage when used in excess, just as all amphetamines can. Ecstasy is popular at raves and parties for its ability to give energy and increase feelings of well-being. It can cause intimacy among users and feelings of love or empathy as well as decreased feelings of fear and anxiety. 
Ephedrine is a molecule that was banned in the United States because of its similar structure to aphetamine and methamphetamine. Though it is not an amphetamine itself, ephedrine was used as a primary ingredient in the creation of methamphetamine, which is a very potent form of amphetamine. Ephedrine was found in diet pills that were found by the United States court system to have been the cause of heart related death.  Since ephedrine was made illegal, pseudoephedrine — a synthetic form of ephedrine– has been made a controlled over the counter substance. In the U.S. people must be at least 18 years old to buy pseudoephedrine products, which are still used by some to create methamphetamine.
The coca plant is the source for cocaine, which is derived from it’s leaves. Cocaine is a stimulant and appetite suppressant. Cocaine was seen as a miracle drug toward the end of the 19th century. Sigmund Freud and other professionals of the time believed that it should be used for everything from depression to fatigue. Many over the counter products began to have cocaine and in 1886, Coca Cola was released with cocaine as the root of its name and a key ingredient in the drink. Unfortunately, cocaine is extremely habit forming and can have adverse effects on both health and personality. After complaints from southern slave owners and people witnessing the sporatic violence and aggressiveness cocaine can cause, the United States government set out to ban the substance. It is still a very popular drug in the United States even though it is illegal.
Cocaine is a dopamine reuptake inhibitor, a noradrenaline reuptake inhibitor and a serotonin reuptake inhibitor.  As a result, it causes the brain to be filled with dopamine, noradrenaline, and serotonin which are all pleasure causing molecules. Cocaine increases blood pressure and heart rate, which in turn greatly increases the chances of having a heart attack. Prolonged cocaine use also causes hallucinations and paranoid delusions. 
Hallucinogens are divided into three different categories; psychedelics, dissociatives, and deliriants. They each cause some kind of change in consciousness that often involves hallucinations or altered perception of sensory inputs, but each category does it in a different way.
LSD, magic mushrooms (psilocybin), DMT, and mescalene are all examples of psychedelic drugs. They have the ability to remove barriers our mind has between the senses and the conscious brain. This results in sensory overload, which offers a whole new perspective on the world. Colors are vibrant, shapes shift, and mental processes are modified. Psychedelics are often dependent on the current state of mind of the user, their environment, etc. People can either end up having positive trips where euphoria and insights are gained or bad trips where fear and discomfort consume them. Some people believe that psychedelics can be used for spiritual and religious gains.  This is most likely because there is so much new information flooding the mind that they feel like they are experiencing something from a higher power or from another dimension/world. Effects from psychedelics can sometimes last for many hours or days.
LSD is perhaps the most well known of the psychedelics. It interferes with serotonin flow in the brain. This excites the cortex and increases input from the thalamus.
Psychedelics took away the barrier between the subconscious and conscious brain. Dissociatives put up barriers between the subconscious and conscious areas of the brain, which results in sensory deprivation. People who use dissociatives find that it creates heightened levels of introspection, out of body experiences, and hallucinations.  They are also used as anaesthetics. Some examples of dissociative drugs are nitrous oxide ketamine, and PCP. Nitrous oxide is also called “laughing gas” because of its anasthaetic and analgesic effects, which can cause people to feel like laughing for no particular reason. Ketamine blocks NDMA receptors and targets opioid receptors. This causes hallucinations and loss of consciousness.
Deliriants cause people to enter a state of psychosis or lucid dreaming. They can be the most hallucinogenic drugs. One deliriant, called atropine, binds to receptors that acetylcholine normally would. Since there are so many of these receptors in our brains, atropine carries many unpleasant side effects. Deliriants are not very popular recreational hallucinogens.
Clinical depression is a very serious problem. Though psychotherapy and counseling help, there are times when it isn’t enough and a chemical drug is required to help someone feel better. Other times people are too busy or ashamed to seek therapy for their unhappiness. They would rather get a prescription and be done with it. Antidepressants are mostly non-addictive drugs which work in subtle ways to increase one’s levels of happiness. They can also be used to lower anxiety. Antidepressants can be used during a hard time in one’s life as a way to cope with a recently traumatic event like the loss of a loved one. Afterward, the person can either abruptly stop taking the antidepressant or slowly wean themselves off. It is usually best to wean so that no adverse psychological or physiological reactions occur. There are three main categories for antidepressants, depending on how they work.
Not used as much in modern medicine as they used to be, tricyclics were discovered in 1957.  They are easier to overdose on than other forms of antidepressants. They work by blocking the reuptake systems for serotonin and noradrenaline. This leaves more serotonin and noradrenalin in the brain which in turn improves a person’s mood. It takes several weeks for tricyclics to begin working. They are often problematic because they can cause many unwanted side-effects like constipation, drowsiness, and bladder problems. They are still prescribed sometimes today for use in pain or for those that find all other forms of antidepressants useless.
Monoamine Oxidase Inhibitors
MAOIs are proteins that stop the actions of MAO-A.  MAO-A destroys serotonin, noradrenaline, and dopamine. Once MAO-A is blocked by an MAOI, the levels of these neurotransmitters will increase and the person’s happiness levels will go up. Those taking MAOIs often have to be very careful about what they eat or what drugs/chemicals they put into their bodies. If tryptophan or tyramine are taken while one is on an MAOI then stroke or hyperserotonemia can occur, both of which can be deadly.
Serotonin Reuptake Inhibitors
SSRIs focus on increasing serotonin only. One of the most well known SSRIs is Prozac, which is a name that has become synonymous with the word depression. There are other SSRIs like Celexa and Zoloft which are also well known. SSRIs have gotten a lot of media attention because of the numbers at which they are prescribed. Also, there have been recent studies released that show most all SSRIs besides Prozac can increase the amount of suicidal thoughts and attempts in those under the age of 18. 
SSRIs work by blocking the reuptake of serotonin back into the receptor which released it, meaning serotonin accumulates in the brain and eventually improves mood.
Cannabis, or marijuana, is the most popular recreational drug that is illegal in many parts of the world. Around 150 million people consume cannabis every day. It comes from the Cannabis sativa plant and is usually sold in the form of dried budding flower and leaves.  There are other variations to the drug such as hashish, which is concentrated resin from the plant that end up making for a more potent delivery of THC. Tetrahydrocannibinol is the primary chemical behind the psychoactive effects of marijuana. THC binds to a receptor in the brain and throughout the central nervous system called cannabinoid receptor-1 (CB1). Since these receptors are all over the brain, marijuana manages to have a number of different effects on people. It causes well-being, relaxation, hunger, paranoia, memory impairment, slight visual impairment or hallucination, and perceived thought awareness, among other things.
Marijuana is used medicinally to decrease nausea and stimulate hunger in AIDS sufferers. It also manages to eliminate pain in those with arthritis and multiple sclerosis. This is probably linked to whatever function anandamide serves in the brain, which is the nerotransmitter that binds to CB1 when THC is not present.
There have been some studies which show that Cannabis, when used for many years, can hinder one’s ability to create long-term memories and process information. There is also a relatively new study, performed by London’s Institute of Psychiatry, which found that 25% of teenage cannabis smokers increased their likeliness of developing psychotic disorders like schizophrenia. 
Pain signals are sent from nociceptors in the body and into the brain. Though pain is a natural and many times helpful reaction, it can also be extremely unpleasant. For this reason, analgesics or pain relievers are sought after, developed, and used by many people all over the world.
Non-steroidal anti-inflammatory drugs (NSAID) are used to take away pain and inflammation. Acetylsalicylic acid is another word for aspirin, which is an NSAID that was technically discovered in 1828 but not extracted and put into its present form until 1897. Aspirin has since shown a great deal of medicinal value. Not only does it alleviate pain and reduce fever, but it also helps to protect us from heart disease, strokes, and blood clots.  For its positives, Aspirin also carries risks such as development of peptic ulcers and dyspepsia.
In 1961 a pharmaceutical company discovered Ibuprofen, which has since become a widely used drug for treatment of fever, headaches and inflammation– just like aspirin. Ibuprofen is somewhat safer than aspirin, however, and doesn’t carry the danger of ulcers like aspirin does. Ibuprofen has risks, however, such as stomach bleeding.
NSAIDs block the activity of enzymes which create prostaglandins, which are the chemicals responsible for triggering pain sensation.  Without prostaglandins, nociceptors aren’t stimulated and pain isn’t felt. Both aspirin and ibuprofen are readily available over the counter medications.
Para-acetyl-amino-phenol is the long word for what most people know as Tylenol, which came out in 1955. Paracetamol is believed to block the activity of a member to the cyclooxygenase family of enzymes which prostaglandins.  As we know, prostaglandins stimulate nociceptors which then create pain. The cyclooxygenase that Tylenol works on is found only in the brain and spinal cord, which is why paracetamol doesn’t act as an anti-inflammatory.
The opium poppy Papaver somniferum is the source of opium, which is one of the longest used painkiller drugs on earth. There are many derivatives of opium including codeine, morphine, heroin, oxycontin, and more. They are the most powerful analgesics in the world. Opiate drugs bind to opioid receptors located throughout the body and brain. These opioid receptors are at the synaptic terminal of neurons involved with pain. Morphine and its derivatives bind to the synaptic terminals and make it impossible for pain signals to get into the neuron, which eliminates any feelings of discomfort or pain.
Opium is highly addictive and users build up tolerance. One of the most powerful drugs, heroin, is also one of the deadliest. People usually smoke heroin or inject it straight into their veins. They recieve feelings of immense euphoria and relaxation. Once those feelings go away, they want them back again. Pretty soon heroin users’ brain chemistry has changed so that they need the drug to feel normal. In the absence of heroin, they go into withdrawal. This involves vomiting, convulsions, body pain, insomnia, muscle spasms and more. Other opium related drugs work similarly to heroin, which is why they are very carefully prescribed and regulated in countries like the United States. Many people die or become addicted to opium drugs every year.
Schizophrenia and delusion disorders are examples of disorders which cause psychosis. Psychosis is when someone’s perception of reality has become affected. Antipsychotic drugs attempt to counteract psychosis. Chlorpromazine, also called thorazine, was one of the first antipsychotics to ever be developed and used. It successfully helped those with psychotic disorders lead relatively normal lives by keeping their psychosis under control. Since chlopromazine there have been other antipsychotic medications such as olanzapine (Zyprexa) which have also helped to make disorders such as schizophrenia much less invasive on life. 
There are two kinds of antipsychotics, those that are called “typical”, like thorazine, and those that are “a-typical” like Zyprexa. Antipsychotics work by blocking D2 receptors in the meso limbic pathway of the brain. By blocking the dopamine receptors in the mesolimbic pathway, excess
dopamine is kept out of these regions of the brain. This is thought to
be the main reason antipsychotics work. “A-typical” antipsychotics attempt to block only the D2 receptors in the meso limbic pathway. “Typical” antipsychotics block the meso limbic pathway as well as three other D2 receptor pathways. This results in far more unwanted side effects than seen when using “typical” antipsychotics. Of course, no antipsychotic is perfect and there are negative side effects involved with all of them.
There are many thousands of other drugs that exist in the world today. The ones mentioned in this article are mostly the psychoactive ones most commonly mentioned and considered by popular culture. They can be dangerous or helpful. Some are part of our everyday lives and culture, while others are looked at with disgust and kept a distance. No matter what, drugs are definitely a powerful and pervasive part of human existence.
- Drug: definition, synonyms. Answers.com.
- Synthetic Drug. Britannica Encyclopedia Online.
- Rational drug design. The Human Genome. Wellcometrust.
- Pfizer. Fortune 500. CNN Money
- Blood-Brain Barrier: definition, synonyms... Answers.com
- Natural Reward Pathways Exist in the Brain. University of Utah. Learn Genetics
- Guides, R., (2007). The Rough Guide to the Brain 1. London: Rough Guides.
- Drug Abuse and Addiction: Understanding the Signs, Symptoms, and Effects. HelpGuide.org
- The Loss of Joy: Anhedonia. Mental Health Matters.
- Alcohol Prohibition Was a Failure. Thornton, Mark. Cato Institute.
- Alcohol Damages Day-To-Day Memory Function Heavy Drinkers Make Significantly More Memory Mistakes. T, Buddy. About.com. 2006
- Alcohol and your health: Weighing the pros and cons. Mayo Clinic.
- Drugs of Abuse - BARBITURATES. Drug Free Workplace.
- benzodiazepine drug. Britannica Encyclopedia.
- "Benzodiazepine use, abuse, and dependence". O'brien CP (2005). J Clin Psychiatry
- Caffeine Content Of Popular Drinks. Wilstar.com
- Attitudes about caffeine abuse. Search your love
- Tobacco. World Health Organization.
- Tobacco Health Facts. World Health Organization.
- Amphetamine: definition and much more. About.com
- Military looks to drugs for battle readiness. The Christian Science Monitor.
- Ephedrine and its use in Weight Loss. Beckner, Lindsay. Vanderbilt University.
- MDMA (Ecstasy). National Institute on Drug Abuse.
- NIDA InfoFacts: Crack and Cocaine. National Institute on Drug Abuse
- Psychedelics and Religious Experience. Watts, Alan.
- HALLUCINOGENS AND DISSOCIATIVE DRUGS. National Institute on Drug Abuse
- NIDA InfoFacts: Marijuana. National Institute on Drug Abuse.
- Marijuana May Trigger Schizophrenia. Nauert, Rick. Psych Central.
- Aspirin. MedlinePlus.
- GENERIC NAME: acetaminophen. MedicineNet
- Heroin. Basic Facts About Heroin. About.com
- Tricyclic Antidepressants - Medication Family Profile. About.com
- Monoamine Oxidase Inhibitor (MAOI) Information Page. Insight Journal
- Selective serotonin reuptake inhibitors (SSRIs). MayoClinic
- Antipsychotic Medications. National Institute of Mental Health