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Written by Professor Tobias Banaschewski, University of Heidelberg and Central Institute of Mental Health, Mannheim, Germany


  • The presence of comorbidities in childhood and adolescence is associated with more impairment and a worse longitudinal course.
  • Disruptive behavioural disorders (oppositional defiant disorder and conduct disorder) and anxiety are the most common comorbidities in patients with ADHD.
  • Comorbidities should be taken into account when diagnosing patients and planning treatment.

ADHD is a clinically heterogeneous disorder. Both clinical and epidemiological studies show substantially elevated rates of comorbid psychiatric disorders in children, adolescents and adults with ADHD.1-3 The presence of comorbidities in childhood and adolescence is associated with more impairment1 and a worse longitudinal course, e.g. a higher persistence of ADHD into adulthood.4,5 Therefore, clinicians must consider various other conditions as differential diagnoses, as well as assess the patients with ADHD for a wide range of possible coexisting disorders, including both psychiatric and non-psychiatric disorders.6-8

A particularly high comorbidity (up to 50%) exists between ADHD and disruptive behavioural disorders (oppositional defiant disorder and conduct disorder).5,9,10 These disorders can constitute a complication, a differential diagnosis or a comorbid condition.7 In ADHD, a pronounced hyperactive-impulsive symptomatology might constitute a risk factor for subsequent conduct disorder.7

There is also a significant comorbidity with anxiety disorders (up to 25%) and depression (15–20%), which may often be overlooked.5,7,10 The reasons underlying the frequent coexistence of these disorders remain unclear; common genetic risk factors might contribute to this comorbidity.11 Furthermore, failures at school and difficulties with interpersonal relationships may lead to low self-esteem and insecurity in some children.7 When considering the treatment options for cases of ADHD with comorbid depression, the clinician must decide which disorder to address first: if the depression is associated with the most severe impairments, then standard treatment guidelines for depression should be followed first, before the ADHD symptoms are addressed.12,13

Many children with ADHD experience extreme and uncontrolled mood changes that may require specialist referral.7

While comorbidity with paediatric bipolar disorder should be considered, the relationship between ADHD and bipolar disorder is controversial and evidence suggests that severe, non-episodic irritability may actually be a variant of depression.7,14 Children and adolescents with severe, non-episodic irritability, which is associated with severe ADHD core symptoms and symptoms of oppositional defiant disorder, seem to differ from those with bipolar disorder in longitudinal course, family history and pathophysiological mechanisms.7,14 Thus, it is recommended that bipolar disorder is only diagnosed in cases where identifiable manic or hypomanic episodes are present, including a distinct change from baseline mood with concurrent alterations in behaviour.7,14

There is evidence for earlier and increased use of alcohol and tobacco and substance abuse in adolescents with ADHD,15 and a high prevalence of drug abuse or dependency in adults with ADHD (9–40%).7 Whilst controlling for comorbid disorders substantially weakens this association, research has indicated that non-comorbid ADHD may be an independent risk factor for substance use disorders in adolescents and adults.7,15 Treatment plans should address both ADHD and any comorbid substance use disorders, including psychosocial interventions aimed at reducing substance misuse and relapse prevention.12,16

During early school years, children with ADHD have been found to be at an increased risk of developing comorbid tic disorders.7 Conversely, about half of cases of chronic tic disorders also meet criteria for ADHD.7,17 Where the disorders are comorbid, it is usually the ADHD that occurs first (often about 2–3 years before the tic disorder) and determines the degree of psychosocial impairment.7

Children with ADHD may experience a range of other problems.  While the International Statistical Classification of Disease and Related Health Problems 10th revision (ICD-10) precludes the dual diagnosis of ADHD with autistic spectrum disorder,18 studies have clearly demonstrated that ADHD and autistic spectrum symptoms often coexist.7,19,20 As such, the Diagnostic and Statistical Manual of Mental disorders – fifth edition (DSM-5) now recognises autistic spectrum disorder as a differential diagnosis alongside ADHD.21  In addition, population studies indicate that intellectual disability may be more common (up to 5–10 times) in children with ADHD than in those without.7 These children are also at risk for coexisting dyscalculia and language disorders, with major reading and writing difficulties reported in 25–40% of patients with ADHD.7

ADHD is also often accompanied by problems with sensory motor coordination, which may manifest as clumsiness, poor handwriting, poor performance in sports, or delays in achieving motor milestones. Indeed, many children with ADHD fulfil criteria for a developmental coordination disorder. ADHD has also been associated with disturbed sleep and daytime sleepiness.7,22

Comorbid disorders need to be diagnosed and taken into account when planning treatment for patients with ADHD.11,13,16


Disclaimer: The views expressed here are the views of the physician and not those of Shire.

  1. Angold A, Costello EJ, Erkanli A. Comorbidity. J Child Psychol Psychiatry 1999; 40: 57-87.
  2. Costello EJ, Mustillo S, Erkanli A, et al. Prevalence and development of psychiatric disorders in childhood and adolescence. Arch Gen Psychiatry 2003; 60: 837-844.
  3. Kessler RC, Adler L, Barkley R, et al. The prevalence and correlates of adult ADHD in the United States: results from the National Comorbidity Survey Replication. Am J Psychiatry 2006; 163: 716-723.
  4. Lara C, Fayyad J, de Graaf R, et al. Childhood predictors of adult attention-deficit/hyperactivity disorder: results from the World Health Organization World Mental Health Survey Initiative. Biol Psychiatry 2009; 65: 46-54.
  5. Coghill D, Rohde LA, Banaschewski T. Attention-deficit/hyperactivity disorder. In: Banaschewski T, Rohde LA (eds): Biological child psychiatry. Recent trends and developments. Advances in Biological Psychiatry series. Karger, Basel. 2008; Vol. 24: 1-20.
  6. Kutcher S, Aman M, Brooks SJ, et al. International consensus statement on attention-deficit/hyperactivity disorder (ADHD) and disruptive behaviour disorders (DBDs): clinical implications and treatment practice suggestions. Eur Neuropsychopharmacol 2004; 14: 11-28.
  7. Banaschewski T, Rohde L. Phenomenology. In: Banaschewski T, Coghill D, Danckaerts M, et al (eds). Attention-deficit hyperactivity disorder and hyperkinetic disorder. Oxford University Press, New York. 2010; 3-18.
  8. Coghill D, Sergeant JA. Assessment. In: Banaschewski T, Coghill D, Danckaerts M, et al (eds). Attention-deficit hyperactivity disorder and hyperkinetic disorder. Oxford University Press, New York. 2010; 91-106.
  9. Elia J, Ambrosini P, Berrettini W. ADHD characteristics: I. Concurrent co-morbidity patterns in children & adolescents. Child Adolesc Psychiatry Ment Health 2008; 2: 15.
  10. Ambrosini PJ, Bennett DS, Elia J. Attention deficit hyperactivity disorder characteristics: II. Clinical correlates of irritable mood. J Affect Disord 2013; 145: 70-76.
  11. Cole J, Ball HA, Martin NC, Scourfield J, McGuffin P. Genetic overlap between measures of hyperactivity/inattention and mood in children and adolescents. J Am Acad Child Adolesc Psychiatry. 2009; 48: 1094-1101.
  12. Coghill D, Danckaerts M. Organizing and delivering treatment. In: Banaschewski T, Coghill D, Danckaerts M, et al (eds). Attention-deficit hyperactivity disorder and hyperkinetic disorder. Oxford University Press, New York. 2010; 91-106.
  13. Remschmidt H. Global consensus on ADHD/HKD. Eur Child Adolesc Psychiatry 2005; 14: 127-137.
  14. Baroni A, Lunsford JR, Luckenbaugh DA, et al. Practitioner Review: The assessment of bipolar disorder in children and adolescents. J Child Psychol Psychiatry 2009; 50: 203-215.
  15. Wilens TE, Martelon M, Joshi G, et al. Does ADHD predict substance use disorders? A 10-year followup study of young adults with ADHD. J Am Acad Child Adolesc Psychiatry 2011; 50: 543-553.
  16. Taylor E, Döpfner M, Sergeant J, et al. European clinical guidelines for hyperkinetic disorder – first upgrade. Eur Child Adolesc Psychiatry 2004; 13(Suppl 1): I/7-I/30.
  17. Freeman RD. Tic disorders and ADHD: answers from a world-wide clinical dataset on Tourette syndrome. Eur Child Adolesc Psychiatry 2007; 16(Suppl 1): I/15-I/23.
  18. World Health Organization. The ICD-10 Classification of Mental and Behavioural Disorders. Available at: Last updated 1993; 1: 1-263. Accessed 05 January 2017.
  19. Reiersen AM, Constantino JN, Todd RD. Co-occurrence of motor problems and autistic symptoms in attention-deficit/ hyperactivity disorder. J Am Acad Child Adolesc Psychiatry 2008; 47: 662-672.
  20. Ghanizadeh A. Co-morbidity and factor analysis on attention deficit hyperactivity disorder and autism spectrum disorder DSM-IV-derived items. J Res Med Sci 2012; 17: 368-372.
  21. American Psychiatric Association: Diagnostic and statistical manual of mental disorders, fifth edition. Arlington, VA, American Psychiatric Association, 2013.
  22. Cortese S, Konofal E, Yateman N, et al. Sleep and alertness in children with attention-deficit/hyperactivity disorder: a systematic review of the literature. Sleep 2006; 29: 504-511.
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