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23 Red Flags In Teenage Behavior

As parents, we’ve all been there—our once sweet, innocent child suddenly morphs into a moody, eye-rolling, door-slamming teenager, and we’re left wondering what on earth just happened. 

Welcome to the turbulent world of adolescence, when hormones, social pressures, and emotional growth collide, leading to a rollercoaster of emotions and behaviors.

When their teen reaches adolescence, parents have to endure moments of uncertainty that can feel like walking through a dense forest. Red flags, however, can serve as our compass, guiding us toward early intervention and even professional help if necessary.

red flags in teenage behavior teen in depression isolation

Here are some major warning signs that may indicate a problem in a teen.

  1. Drop in academic performance
  2. Excessive isolation
  3. Disruption in sleep patterns
  4. Lose interest in social activities or extracurricular activities once enjoyed
  5. Mood swings or excessive moodiness
  6. Irritability from time to time
  7. Aggressive behaviors
  8. Excessive anger
  9. Excessive risk-taking behaviors
  10. Unusual rebellious behavior
  11. Secretive behavior
  12. Avoidance behaviors
  13. Social isolation
  14. Extreme weight loss or dramatic weight gain
  15. A lack of personal hygiene
  16. Impulsive behavior
  17. Loss of appetite
  18. Feelings of worthlessness or hopelessness
  19. Covering up arms in the summer
  20. Excessive weight concerns
  21. Extreme dieting
  22. Delinquent behavior
  23. Risky sexual behavior

Associated Causes 

Every warning sign can have a number of causes. Therefore, do not jump to conclusions after observing one behavior. 

An isolated red flag might be a mere coincidence. Some behaviors may also be considered typical teen behavior. For instance, common mood swings are normal behavior, but extreme mood shifts are not.

Excessive red flag behaviors or multiple ones often indicate that the teen is grappling with issues or challenges.


Here are some common signs of depression in teens​1​.

  • Excessive sleeping or insomnia
  • Become uninterested in once enjoyable activities
  • Appetite loss
  • Lack of engagement with life
  • Feelings of guilt or worthlessness
  • Chronic low in mood
  • Isolation from family members or stop spending time with friends

General anxiety disorder and other mental health disorders may show similar symptoms. Therefore, if you observe these behaviors, it is important to seek help from mental health professionals.

red flag behaviors sad teenager sitting


Self-injurious or self-destructive behavior is direct and deliberate bodily harm without suicidal intent. Self-injury typically involves cutting or carving the skin to decrease negative emotions or as a cry for help​2​.

Some common warning signs include

  • Unexplained wounds or scars, often in patterns
  • Hiding the skin, such as wearing long sleeves on a hot summer day
  • Being alone in the bathroom or bedroom for a long period
  • Sharp objects such as knives or razor blades hidden in possession
  • Frequent accidental injuries
  • Self-criticism
  • Feelings of helplessness or hopelessness

Self-harm is one of the symptoms of mental illness, such as borderline personality disorder​3​.

It is also associated with adolescent sexual and physical abuse. Seek mental health counseling immediately if you notice these behaviors in your teen​4​.

Eating Disorder

Considerable weight loss is a common sign of eating disorders such as anorexia nervosa and bulimia nervosa.

Major signs of eating disorders are

  • Obsessive weight measuring or calorie counting
  • Patterns of weight loss
  • Intense fear of gaining weight
  • Negative body image

Many teenage girls are concerned about being overweight and may diet inappropriately. However, this is a common behavior for adolescents, and most do not have an eating disorder​5​.

Don’t hesitate to speak to your family health practitioner if you have any doubts.

Substance abuse

Youth abuse of drugs and alcohol is prevalent in the US, and most abuse begins during adolescence​6​.

Substance abuse and mental health conditions often co-occur.

The ability of parents to recognize these red flag signs is important so that early intervention for substance abuse can be sought.

  • Red face, bloodshot eyes, or breath odors of alcohol​7​
  • Lack of personal hygiene
  • Irritability
  • Extreme rage or mood swings
  • In possession of illegal drug
  • Difficulty focusing in school or completing assignments
  • Secretive behavior, such as hiding in the bathroom or bedroom for long periods of time
  • Signs of depression, bipolar disorder, or general anxiety disorder​8​

Also See: Coping Skills for Teens


  1. 1.
    Fava M, Kendler KS. Major Depressive Disorder. Neuron. Published online November 2000:335-341. doi:10.1016/s0896-6273(00)00112-4
  2. 2.
    Nock MK. Self-Injury. Annu Rev Clin Psychol. Published online March 1, 2010:339-363. doi:10.1146/annurev.clinpsy.121208.131258
  3. 3.
    Hodgson S. Cutting through the Silence: A Sociological Construction of Self-Injury. Sociological Inquiry. Published online May 2004:162-179. doi:10.1111/j.1475-682x.2004.00085.x
  4. 4.
    Hawton K, Saunders KE, O’Connor RC. Self-harm and suicide in adolescents. The Lancet. Published online June 2012:2373-2382. doi:10.1016/s0140-6736(12)60322-5
  5. 5.
    Rosen DS. Identification and Management of Eating Disorders in Children and Adolescents. Pediatrics. Published online December 1, 2010:1240-1253. doi:10.1542/peds.2010-2821
  6. 6.
    Burstein M. Use and Abuse of Alcohol and Illicit Drugs in US Adolescents. Arch Gen Psychiatry. Published online April 1, 2012:390. doi:10.1001/archgenpsychiatry.2011.1503
  7. 7.
    Saini G, Prabhat K, Gupta N. Drug addiction and periodontal diseases. J Indian Soc Periodontol. Published online 2013:587. doi:10.4103/0972-124x.119277
  8. 8.
    Simon NM. Generalized Anxiety Disorder and Psychiatric Comorbidities Such as Depression, Bipolar Disorder, and Substance Abuse. J Clin Psychiatry. Published online April 2009:10-14. doi:10.4088/jcp.s.7002.02

Updated on April 11th, 2023 by Pamela Li

Pamela Li is an author, Founder, and Editor-in-Chief of Parenting For Brain. Her educational background is in Electrical Engineering (MS, Stanford University) and Business Management (MBA, Harvard University). Learn more


    * All information on is for educational purposes only. Parenting For Brain does not provide medical advice. If you suspect medical problems or need professional advice, please consult a physician. *