The health consequences of alcohol abuse and substance use may be immediate and unpredictable, such as fatalities associated with alcohol poisoning and drug overdose, or more subtle and long term, such as liver and brain damage associated with the prolonged use of alcohol.

In addition to health-related problems, alcohol abuse and substance use are associated with financial difficulties, interpersonal conflicts, domestic violence, deterioration of the family structure, accidental injuries or fatality, and may significantly impact academic and work performance.

Most Commonly Used Drugs and Their Short and Long Term Effects

The following information was compiled from the NIH's National Institute on Drug Abuse. 

Alcohol and Other Depressants [barbiturates, sedatives, and tranquilizers]

Alcohol, tranquilizers, and sedatives are all considered depressants. These drugs depress the central nervous system by mimicking either the brain’s natural sedating chemicals or by diminishing the brain’s natural ability to produce stimulating chemicals.
Short-term effects: Alcohol consumption causes a number of marked changes in behavior; even low doses significantly impair judgment and coordination. Moderate to high doses cause significant impairments in higher mental functions, severely altering a person's ability to learn and remember information. Very high doses can cause respiratory depression and death. The effects of other depressants are similar to those of alcohol: large doses can cause slurred speech, poor motor coordination, altered perception, psychosis, hallucinations and paranoid delusions, coma, or death.
Long-term effects: Long-term effects of using alcohol include addiction, depression, accidents as a result of impaired ability, ulcers, gastritis, pancreatitis, fatty liver, alcoholic hepatitis, chronic active hepatitis, and cirrhosis. Long-term use of other depressants can also lead to addiction, including both physical and psychological dependence. Regular use over time may result in a tolerance to the drug. Withdrawal symptoms may range from restlessness, insomnia, and anxiety, to convulsions and death.

Nicotine

Nicotine, one of more than 4,000 chemicals found in the smoke from tobacco products, is the primary component in tobacco that acts on the brain. Nicotine is absorbed through the skin and mucosal lining of the mouth and nose or by inhalation in the lungs. Nicotine increases the levels of dopamine in the brain. The acute effects of nicotine dissipate in a few minutes, causing the smoker to continue dosing frequently throughout the day to maintain the drug’s pleasurable effects and prevent withdrawal.
Effects:  Select effects include addiction, high blood pressure, emphysema, heart and lung disease, and cancer.

Marijuana

THC [delta-9-tetrahydrocannabinol] stores itself in the fatty tissue of the brain, reproductive organs, liver, lungs, and spleen, where it causes tissue damage and hinders normal body function. In the brain, THC widens the gaps between nerve cells causing decreased transmission of impulses.
Effects:  Use can result in speech problems, memory and learning problems, physical impairment, and can interfere with judgment, and cause difficulty thinking and solving problems. Use can also elevate anxiety and cause a panic reaction. Long-term use can cause permanent memory problems. There is also an increased risk of developing respiratory problems including, but not limited to, cancer.

Stimulants [Cocaine, Amphetamines, “speed,” “uppers”]

Cocaine use interferes with reabsorption of dopamine causing euphoria, which constricts blood vessels, dilates pupils, and increases heart rate and blood pressure.
Effects: Acute cardiovascular or cerebrovascular emergencies such as heart attack or stroke can result from use, regardless of frequency. Cocaethylene, created by the liver when cocaine and alcohol are used, increases the chance of sudden death. Addiction, lung damage, depression, paranoia, and toxic psychosis are also possible. Similar risks are presented by the use of speed and uppers.

Ecstasy [MDMA, Molly]

Ecstasy is a synthetic drug, and is similar to both methamphetamine and mescaline, which is a hallucinogenic.
Effects:  The drug mainly affects the body by affecting neurons that use the chemical serotonin, which can greatly affect mood, aggression, sexual activity, sleep, and sensitivity to pain. In high doses, MDMA can interfere with the body’s ability to regulate temperature, which can lead to a sharp increase in body temperature [hyperthermia], resulting in liver, kidney, and cardiovascular system failure.

Hallucinogens [LSD, PCP]

PCP is a white crystalline powder that is readily soluble in water or alcohol. LSD [lysergic acid diethylamide] is manufactured from lysergic acid, which is found in ergot, a fungus that grows on rye and other grains. The effects of these substances are unpredictable, and depend on the amount taken, the user’s personality and mood, and the surroundings in which the drug is used.
Short-term effects: These drugs alter users perception of time and space by changing the way the brain interprets stimulus. They also increase heart rate and blood pressure, which can lead to coma, or heart and lung failure. High doses can cause symptoms that mimic schizophrenia, such as delusions, hallucinations, paranoia, disordered thinking, a sensation of distance from one’s environment, and catatonia. Speech is often sparse and garbled. PCP can be addictive.
Long-term effects: Flashbacks can occur days, months, or even years after use. Users can also experience decreased motivation, prolonged depression, increased anxiety, increased delusions and panic, and psychosis such as schizophrenia or severe depression.

Narcotics [Opium, morphine, codeine, heroin]

Narcotics include opium, opium derivatives, and semi-synthetic substitutes of opium derivatives. Narcotic use is associated with a variety of unwanted effects including drowsiness, inability to concentrate, apathy, lessened physical activity, constriction of the pupils, dilation of the subcutaneous blood vessels causing flushing of the face and neck, constipation, nausea and vomiting, and most significantly, respiratory depression. As the dose is increased, the subjective, analgesic [pain relief], and toxic effects become more pronounced.
Short-term effects: Short term effects include restlessness, irritability, loss of appetite, nausea, tremors, and drug craving.
Long-term effects: Long term effects include addiction, accidental overdose, risk of hepatitis and AIDS infection from contaminated needles.

Prescription Drug Abuse

The most commonly misused prescription drugs are:

Painkillers [codeine, Ocxycontin, Vicodin, Demerol]; CNS depressants [Nembutal, Valium, Xanax]; and stimulants [Ritalin, Dexedrine, Adderall].
Short-term effects: Stimulants and CNS depressants present risks for irregular heartbeat, greatly reduced heart rate, seizures, dangerously increased body temperature, and can cause aggressive or paranoid behavior.
Long-term effects: The greatest risk from these drugs is the significant chance for dependence. This can lead to greater doses and increased frequency of use. Attempting to cease use without proper medical help after dependence has been established can be dangerous and even fatal.

Inhalants [gas, aerosols, glue, nitrites, nitrous oxide]

Inhalants are breathable chemical vapors that produce psychoactive effects. A variety of products common in the home and in the workplace contain substances that can be inhaled:

• Solvents:  paint thinners or removers, degreasers, dry-cleaning fluids, gasoline, and glue
• Art or office supply solvents:  correction fluids, felt-tip-marker fluid, and electronic contact cleaners
• Gases [used in household or commercial products]:  butane lighters and propane tanks, whipped cream aerosols [whippets], and refrigerant gases
• Household aerosol propellants:  contained in items such as spray paints, hair or deodorant sprays, fabric protector sprays, and aerosol computer cleaning products
• Medical anesthetic gases:  ether, chloroform, halothane, and nitrous oxide
• Nitrites:  volatiles including cyclohexyl, butyl, and amyl nitrites, and are commonly known as “poppers.” Volatile nitrites are often sold in small brown bottles and labeled as “video head cleaner,” “room odorizer,” “leather cleaner,” or “liquid aroma.”

Short-term effects: These chemicals slow down the body’s functions, and can cause momentary intoxication which, if continued, can lead to stimulation, reduced inhibition, and ultimately loss of consciousness. Using solvents or aerosol sprays can induce heart failure and death, known as “sudden sniffing death.” This effect is mostly associated with butane, propane, and chemicals in aerosols.
Long-term effects: These chemicals can cause severe damage to the brain, liver, and kidneys. Specifically, they can cause hearing loss, peripheral neuropathies [limb spasms], central nervous system damage, and even bone marrow damage.

GHB

GHB [gamma hydroxybutyrate] is a central nervous system depressant. It is made from gamma butyrolactone and sodium or potassium hydroxide, which means that it is essentially degreasing solvent or floor stripper combined with drain cleaner. In liquid form it is usually clear and looks like water. GHB and two of its precursors, gamma butyrolactone [GBL] and 1,4 butanediol [BD] have been characterized as predatory drugs used to commit acts of sexual violence.
Effects: Abuse of GHB can cause amnesia, coma and/or seizures, inability to move, or impaired speech. There is also a risk of death, especially when combined with alcohol or other drugs.

Further information on specific drugs is available on the Drug Enforcement Administration website.