Understanding Coexisting Conditions in Children and Teens with ADHD

By Gene Carroccia, Psy.D., Licensed Clinical Psychologist

When someone has ADHD, this is often not the full story. Many do not know that ADHD is a foundational disorder that frequently has one or more coexisting conditions. There are a number of medical, sleep, psychological, substance use, trauma, neurodevelopmental, sensory processing, and fetal substance exposure conditions which can occur with and worsen true ADHD. Between 67 to 80% of clinic-referred children and 80% or more of adults with ADHD have at least one additional disorder, up to 50% have two or more other conditions, and 20% have three or more coexisting disorders. Consequently, families should expect other conditions to occur along with ADHD.  When other disorders exist along with ADHD, these combinations can magnify ADHD and create more complex difficulties than ADHD by itself. The sum is greater than the parts.


These other conditions may not be identified because ADHD can mask and hide them so they are not recognized as separate disorders. The additional symptoms may be incorrectly assumed to be part of the ADHD and often don’t receive their own treatment. Sometimes true ADHD does not exist, but because many other conditions can cause ADHD-like presentations, a misdiagnosis of ADHD may occur. Clinicians might not screen for and identify the numerous additional conditions as part of their diagnostic process because they do not know about them, or have not been trained to do so. When coexisting conditions are not recognized, improvements can be slow or partial. Difficulties may persist, and families and clinicians can become disheartened. Sadly, these can become barriers to living better lives.


So, what can be done? ADHD and other coexisting conditions should be identified to obtain the best understanding of a person’s overall functioning, challenges, and treatment needs.

Accurately diagnosing ADHD involves identifying all possible existing conditions, and then addressing them in treatment plans, sometimes with multiple providers. Therefore, working with effective diagnostic evaluators is very important. To support an effective and more accurate diagnostic process, the 10-step ADHDology Evaluation Model can be used to assist parents, educators, and providers with information about a comprehensive approach.


If children or adults were told they have ADHD but did not get a thorough evaluation, and/or they question if they have coexisting conditions, it may be time to obtain a new comprehensive ADHD evaluation from a clinical psychologist or experienced masters’ level behavioral health therapist. Other clinicians may be able to provide thorough evaluations as well. A neurodevelopmental psychological testing assessment from a neuropsychologist (not a neurologist physician) could explore other neurodevelopmental conditions and would probably offer the most definitive answers, but these are costly and there are fewer providers. As part of the diagnostic process, other providers may need to contribute additional evaluations, such as:

  • Occupational therapy evaluations (for sensory processing and motor coordination conditions)
  • Speech-language pathologist evaluations (for speech and expressive/receptive language deficits)
  • Developmental or behavioral optometrist evaluations (for visual processing deficits)
  • Audiologist evaluations (for auditory processing deficits)
  • Ears, Nose, and Throat (ENT) physician examinations (to explore sleep apnea, chronic mouth breathing, allergies, and congestion)
  • Neurologist examinations (for head injuries, seizures, and tic disorders)
  • Medical examinations by primary care physicians (see below for the medical conditions)
  • Sleep studies (mouth breathing, sleep apnea, and other sleep conditions)


Some of the most common coexisting conditions with ADHD for children and teens include:

  • A range of sleep problems (including insomnia and inadequate hours of sleep)
  • Sleep-disordered breathing (chronic mouth breathing and sleep apnea)
  • Anxiety conditions
  • Depressive disorders
  • Dysgraphia (significantly impaired and messy handwriting)
  • Oppositional defiant disorder
  • Learning disorders
  • Gaming disorder (video game addiction)
  • Fetal substance exposure conditions
  • Substance misuse for adolescents
  • Speech and language deficits
  • Fine and/or gross motor deficiencies
  • Nighttime bedwetting
  • Sensory processing disorders (see below)


When obtaining an ADHD evaluation or a more comprehensive ADHD neurodevelopmental testing assessment, providers should explore if the following conditions are present.  These may coexist and worsen ADHD, or cause ADHD-like symptoms when true ADHD does not exist.  Additionally, if these conditions currently exist, families and providers should determine if these conditions are effectively addressed and managed so they do not exacerbate true ADHD or are causing ADHD-like symptoms when true ADHD does not exist.

  • Medical Conditions
    • Vision difficulties
    • Hearing difficulties
    • Nasal allergies and related medication use
    • Chronic sinus problems
    • Asthma and related mediation use
    • Enlarged tonsils and adenoids
    • Diabetes
    • Hypoglycemia
    • Anemia and iron deficiency
    • Thyroid conditions
    • Persistent/recurrent ear infections
    • Toxic heavy metals exposure (such as lead, mercury, cadmium)
    • Deficiencies in iron, zinc, magnesium, B vitamins (including B6 and not just B12, which is the easiest to test for), and D vitamin
    • Food allergies and sensitivities
    • Seizures
    • Head injuries
    • Conditions causing chronic bodily pain or discomfort
    • Hunger, food insecurity, and malnutrition
    • Other prescription or over-the-counter medication use
    • Medical conditions associated with higher risks of ADHD or ADHD-like presentations, including Phenylketonuria (PKU); Strokes; Meningitis, encephalitis, or other brain diseases, infections, or tumours; Lyme disease; Celiac disease; Leukemia, head and neck cancer treatments; and Fragile X syndrome
  • Sleep Conditions
    • Sleep-disordered breathing, including Snoring, Chronic mouth breathing, and Obstructive sleep apnea
    • Increased nocturnal motor activity
    • Periodic limb movement disorder
    • Restless legs syndrome
    • Insomnia and sleep initiation difficulties
    • Inadequate hours of sleep/chronic inadequate sleep duration
    • Delayed sleep-phase disorder
    • Parasomnias, including Bedwetting, Sleep walking and talking, Night terrors, Bruxism (teeth grinding or clenching), Sleep paralysis, Confusional arousal, and Rhythmic movement disorder
  • Neurodevelopmental Conditions
    • Learning disorders, including Reading learning disorder, Mathematics learning disorder, and Written expression learning disorder
    • Concentration deficit disorder
    • Nonverbal learning disorder
    • Slow processing speed and deficits
    • Dysgraphia
    • Speech and articulation deficits
    • Expressive language disorder
    • Receptive language disorder
    • Tourette’s disorder and tic disorder
    • Giftedness (not a true neurodevelopmental condition)
    • Intellectual disability
    • Autism spectrum disorder – Level 1 (formerly Asperger’s syndrome)
  • Sensory Processing and Motor Disorders
    • Auditory processing disorder
    • Visual processing disorder
    • Tactile and gustatory processing disorder
    • Olfactory processing disorder
    • Vestibular processing disorder
    • Proprioceptive processing disorder
    • Sensory-based motor disorder – Dyspraxia
    • Sensory-based motor disorder – Postural disorder
    • Immature symmetric tonic neck reflex
  • Prenatal Substance Exposure
    • Fetal alcohol spectrum disorders and prenatal alcohol exposure
    • Prenatal nicotine exposure
    • Prenatal marijuana, cocaine, opioid, methamphetamine and amphetamine exposure
  • Psychological Conditions
    • Anxiety disorders
    • Social anxiety disorder
    • Obsessive compulsive disorder
    • Children ages 3 to 6 with school and/or nap transitions
    • Depressive disorders
    • Bipolar disorder
    • Oppositional defiant disorder
    • Conduct disorder
    • Substance use
    • Gaming disorder (video game disorder or addiction)
  • Psychological Traumatic Exposures
    • Physical abuse
    • Sexual abuse
    • Emotional/psychological maltreatment/abuse
    • Bullying experiences
    • Medical trauma
    • Traumatic parental separation or divorce experiences
    • Unstable or highly dysfunctional family environments
    • Recent or current significant family traumas, stressors, and experiences
    • Traumatic grief
    • Other types of traumas
  • Dissociation
  • Neglect
  • Attachment Disorders
    • Reactive attachment disorder
    • Disinhibited social engagement disorder
  • Early Pathogenic Care During the First Five Years of Life

If you would like more information on the 10-step ADHDology Evaluation Model and other related topics, please visit www.ADHDology.com or obtain my book, Evaluating ADHD in Children and Adolescents.


What is this book about?


Evaluating ADHD in Children and Adolescents: A Comprehensive Diagnostic Screening System was published in 2020 by Charles C Thomas. It is the ADHD diagnostic guide that assists clinicians to accurately conduct evidence-based ADHD evaluations, as well as identify and better understand the numerous other possible coexisting conditions that may present along with and worsen true ADHD, or cause ADHD-like presentations when ADHD does not exist.



Back book cover


This book is the ADHD diagnostic guide that helps clinicians provide comprehensive, accurate, and evidence-based ADHD evaluations for children and adolescents. It has three parts:

Part I presents the 10-Step ADHDology Evaluation Model to conduct evaluations and communicate findings with other providers.

Part II describes the numerous medical, sleep, neurodevelopmental, sensory processing, fetal substance exposure, psychological, trauma, and neglect conditions which can coexist with and even worsen true ADHD, or cause ADHD-like presentations when ADHD does not exist.

Part III is the Comprehensive Diagnostic ADHD Screening System (CDASS), a unique approach that utilizes user-friendly checklists to accurately evaluate ADHD by identifying its indicators, associated risk factors, and the conditions in Part II. The purchaser of this book can photocopy and use these checklists without additional cost.


This book will help you:

  • Confidently conduct ADHD evaluations
  • Identify conditions that coexist with, worsen, or mimic ADHD
  • Improve the accuracy of diagnosing ADHD and other conditions
  • Better understand and provide referrals for other suspected conditions