Drug abuse: In the context of international drug control, drug abuse constitutes the use of any substance under international control for purposes other than medical and scientific, including use without prescription, in excessive dose levels, or even an unjustified period of time. (UNODC)

What is drug abuse and substance abuse?
Drug abuse, also known as substance abuse, involves the repeated and excessive use of a drug to produce pleasure or escape reality—despite its destructive effects. The substances abused can be illegal drugs such as marijuana and cocaine, or legal substances used improperly, such as prescription drugs and inhalants like nail polish, glue or gasoline. But whatever the drug of choice, substance abuse can be identified by the maladaptive way in which it takes over the user's life, disrupting his or her relationships, daily functioning, and peace of mind.
For those in the grips of drug abuse and addiction, their drug controls them, not the other way around.

Drug addiction can be physical, psychological, or both. The Substance Abuse and Mental Health Services Administration refers to psychological dependence as “the subjective feeling that the user needs the drug to maintain a feeling of well-being." Using a drug to numb unpleasant feelings, to relax, or to satisfy cravings are examples of psychological addiction. On the other hand, physical dependence refers to the physiological effects of drug use. Physical addiction is characterized by tolerance—the need for increasingly larger doses in order to achieve the initial effect—and withdrawal symptoms when the user stops.

What are the signs and symptoms of drug addiction and abuse?
The more drug use begins to affect and control a person's life, the more likely it is that he or she has a drug problem. Unfortunately, substance abusers are often the last ones to recognize their own symptoms of dependence and addiction. If you suspect that a friend or loved one is abusing drugs, it's important to remember that drug abusers often try to conceal their symptoms and downplay their problem. But there are a number of warning signs you can look for:

• Inability to relax or have fun without doing drugs.
• Sudden changes in work or school attendance and quality of work or grades.
• Frequently borrowing money, selling possessions, or stealing items from employer, home, or school.
• Angry outbursts, mood swings, irritability, manic behavior, or overall attitude change.
• Talking incoherently or making inappropriate remarks.
• Deterioration of physical appearance and grooming.
• Wearing sunglasses and/or long sleeve shirts frequently or at inappropriate times.
• No longer spending time with friends who don't use drugs and/or associating with known users.
• Engaging in secretive or suspicious behaviors, such as making frequent trips to the restroom, basement, or other isolated areas where drug use would be undisturbed.
• Talking about drugs all the time and pressuring others to use.
• Expressing feelings of exhaustion, depression, and hopelessness.
• Using drugs first thing in the morning.

What are the signs and symptoms of drug use and abuse in teens?
There are several telltale signs of possible drug use or abuse in teenagers. The challenge for parents is to distinguish between the normal, sometimes volatile ups and downs of adolescent development and the red flags of substance abuse.

According to the National Drug Intelligence Center, sudden or extreme changes in personality, appearance, school performance, or extracurricular activities may indicate teen drug use. For example, a previously well-behaved, respectful teenager may become emotionally volatile, hostile, or violent. A teenager who is abusing drugs may also withdraw from family and friends, drop previously-enjoyed activities, and neglect schoolwork. Secretive behavior and lying to cover up drug use is also common. In addition, teen drug users may steal, ask for money, or sell valuable possessions in order to support their habit.

Warning Signs of Teen Drug Use

• Negative changes in schoolwork, missing school, or declining grades.
• Increased secrecy about possessions or activities.
• Use of incense, room deodorant, or perfume to hide smoke or chemical odors.
• Subtle changes in conversations with friends (more secretive, using “coded” language).
• New friends.
• Change in clothing choices — new fascination with clothes that highlight drug use.
• Increase in borrowing money.
• Evidence of drug paraphernalia, such as pipes and rolling papers.
• Evidence of inhaling products and accessories, such as hairspray, nail polish, correction fluid, paper bags and rags, and common household products.
• Bottles of eyedrops, which may be used to mask bloodshot eyes or dilated pupils.
• New use of mouthwash or breath mints to cover up the smell of alcohol.
• Missing prescription drugs — especially narcotics and mood stabilizers.

Why do people use and abuse drugs?
There are many reasons why people use drugs. Some people use drugs because they like the rush it gives them or because they are thrill-seekers. Others may try a drug out of curiosity or because their friends do it. However, many people use drugs in order to cope with unpleasant emotions and the difficulties of life. In fact, the National Alliance on Mental Illness estimates that around 50% of drug abusers also suffer from a mental illness such as depression, anxiety, bipolar disorder, or schizophrenia.

People who are suffering emotionally use drugs—not in order to get high—but to feel normal. Drug use can be a seemingly attractive and easy escape from all kinds of problems. Speed might be used to fight feelings of inferiority, sleeping pills to deal with panic attacks, or painkillers to numb depression. However while drug use might make a person feel better in the short-term, this attempt to self-medicate ultimately backfires. Instead of treating the underlying problem, drug use simply masks the symptoms. Take the drug away and the problem is still there, whether it be low self-esteem, stress, or an unhappy family life. Furthermore, prolonged drug use eventually brings its own host of problems, including major disruptions to normal, daily functioning. Unfortunately, the psychological, physical, and social consequences of drug abuse and dependence are often worse than the original problem the user was trying to cope with or avoid.


References

Helpguide.org – Drug Abuse and Addiction: Signs, Symptoms, and Effects

Definition:
UNODC: http://www.unodc.org/pdf/report_2000-11-30_1.pdf

Table:
UNODC: http://www.unodc.org/unodc/en/world_drug_report.html