Editor’s note: This is the first of a two-part column.

I’ve heard the questions dozens of times: How can I tell if my child is in trouble with drugs? How do I separate what is “normal” adolescent behavior from what might be drug-related behavior?

When kids use drugs regularly, certain telltale symptoms begin to appear. Over time, as the brain gradually becomes dependent on drugs (physically needing the drugs to function normally), the adolescent’s thoughts, emotions and actions will be affected in characteristic ways.

I compiled this list of symptoms to help parents determine if their child might have a drug problem. Because it’s a long, detailed list, the second half will appear in my next column.

ANXIETY: Anxiety is universal in kids who use drugs regularly. Many drugs cause physical changes (increased pulse rate, body temperature changes) that contribute to anxiety, and all addictive drugs can create feelings of apprehension, dread, fear, panic and paranoia, especially during the withdrawal phase. Symptoms of anxiety include irritability, emotional instability, mood swings, mental confusion and panic attacks.

BLOODSHOT EYES: Alcohol, marijuana and inhalants cause tiny blood vessels in the eyes to swell and burst, leading to red, bloodshot eyes. Stimulant drugs (cocaine, methamphetamines, Ritalin) can interrupt normal sleep patterns, another cause of bloodshot eyes. Lots of Visine containers around the house or in cars or backpacks should raise suspicion.

CRAVING: Kids call it “feening” or “fiending,” and like all these symptoms, craving gets worse as drug use continues. When young people first start using alcohol or other drugs, they may crave the pleasure, euphoria, relaxation and/or stimulation associated with using drugs. As drug use increases, craving for drugs represents a true physiological need for the drug caused by changes in brain chemistry and function.

DEFENSIVE: Adolescents with a drug problem will fiercely protect their right to use drugs, resist attempts to discuss their use, react with suspicion or hostility when confronted and generally shield their behaviors from prying eyes.

EMOTIONAL HIGHS AND LOWS: Emotions change rapidly and often take uncharacteristic forms. Normally shy and sensitive adolescents may become loud-mouthed and belligerent. Friendly, outgoing kids may become hostile and paranoid. Intense emotional ups-and-downs often occur during the withdrawal period (hours, days, weeks or even months after using) and may include irritability, anxiety, depression, fear and paranoia.

FEAR: As drug use continues, mild apprehension or nervousness often intensifies to chronic anxiety, suspiciousness and an overall sense of dread.

GASTROINTESTINAL COMPLAINTS: The gastrointestinal system — basically all the organs involved in processing and eliminating wastes — is hit hard by drug use. Symptoms of GI distress include nausea, abdominal cramping, loss of appetite, vomiting, diarrhea, constipation and indigestion.

HARDHEADEDNESS: Adolescent drug users are notoriously hardheaded — stubborn, willful, headstrong and obstinate. Every conversation, it seems, ends in an argument. Defiance and bullheadedness are often typical of adolescent behavior, but with drug-using kids, even a simple question or statement of loving concern can lead to full-scale battles.

INSOMNIA: Drugs interfere with sleeping patterns, and adolescent drug users often complain of insomnia, restlessness, interrupted sleep and vivid nightmares. Hoping to fix the problem, they may use calming or sedating drugs such as sedatives, tranquilizers or sleeping pills.

JOYLESSNESS: As the adolescent’s drug use continues and escalates, feelings of gloom and doom begin to cloud almost every aspect of life. Guilt, shame, depression and despair intensify as drug use continues and escalates.

KEEPING TO ONESELF: Adolescent drug users often spend a great deal of time alone, hiding away from prying eyes, locking themselves in their rooms, refusing to show up for meals or family events. Over time, the adolescent becomes increasingly tight-lipped and secretive.

LEGAL PROBLEMS: Problems with the police and the juvenile justice system are common and include (but are definitely not limited to) truancy, possession, stealing, vandalism, drunk and disorderly conduct, assault and DUIs.

MONEY PROBLEMS: Both legal drugs (alcohol, tobacco, vaping products and, in certain states, marijuana) and illegal drugs are expensive. When adolescents use regularly, they go through cash fast. They may sell or pawn their (or your) possessions or steal from friends, relatives or strangers to buy drugs. As drug use progresses into addiction, tolerance increases, and they will need to use more of the drug to feel the same effects and/or to delay the pain and misery of withdrawal.

NERVOUSNESS: When adolescents use regularly, they are often apprehensive, tense, restless and jittery. Stimulant drugs such as cocaine, amphetamines and meth are most likely to cause physical agitation when the user is high, but all addictive drugs will cause jittery nerves during withdrawal which, again, can continue for months after drug use ends.

OBLIVION: Adolescents in trouble with drugs are typically preoccupied, forgetful and absorbed in their own thoughts. The only thing that really matters is drugs — getting them, using them, getting more of them. As one former user explains, “Everything else fades into oblivion.”

Another “O”? OBSESSION: As a wise treatment professional put it (speaking not just about adolescents), “One half of an addicted person’s mind is in the business of manufacturing BS. The other half is in the business of buying it.”

Kathy Ketcham has written 17 books, 11 specifically on addiction and recovery. In 1999, she began leading educational groups at the Juvenile Justice Detention Center, and in 2009, she founded the local nonprofit Trilogy Recovery Community (trilogyrecovery.org), where she continues to volunteer. To find out more visit katherineket