Comorbidity and ADHD
As mentioned above, learning disabilities and ADHD frequently are present simultaneously; however, multiple other mental disorder often co-occur, as well. Common disorders that co-occur with ADHD include oppositional defiant disorder (ODD), conduct disorder, anxiety disorders, depression, disruptive mood dysregualtion disorder, intermittent explosive disorder, obsessive-compulsive disorder, tic disorders, autism spectrum disorder, and substance use disorder.
Perhaps, the most common disorder that may co-occur with ADHD appears to be ODD. Studies report that ODD is present in about 50% of children with ADHD (combined type), while conduct disorder is present in 25% of adolescents with ADHD (combined type). Since ODD is more apparent in ADHD combined type than inattentive type, there appears to be a link between the hyperactivity/impulsivity aspects of ADHD combined type and ODD. Note that if conduct problems are present in adolescents, a diagnosis of conduct disorder should be used instead of ODD, while ODD is used for children. The decrease in conduct problems (at least in diagnosable conduct problems), as indicated above, suggests that some children with ADHD and comorbid ODD learn to manage their conduct problems into adolescents, even though their ADHD continues persists (American Psychiatric Association, 2013).
Research has examined comorbidity with ADHD--specifically, ODD/CD (Oppositional Defiant Disorder/Conduct Disorder), depression, and anxiety. The purpose was to determine if comorbidity with ADHD may actually represent unique disorders; therefore, warranting a separate category of a mental disorder or at least a subcategory.
Cantwell’s Approach
Researchers used Cantwell’s approach as a guideline to determine if a disorder represent a separate distinct disorder. This approach provides criteria for how a disorder could be consider distinct from other disorders. The guidelines are as follows: Clinical pharmacology, demographic correlates, psychosocial correlates, family factors, biological factors, response to treatment, and clinical outcomes.
Prior research by Jensen et al pointed toward evidenced to support the idea that ADHD with ODD/CD constitutes a unique subtype. Other research found that ADHD with mood disorders, as well as ADHD with ODD/CD may constitute subtypes of ADHD. It found that these clients responded differently to treatment. For example, ADHD with mood disorders responded to all treatments. ADHD with ODD/CD responded only to medications and behavior therapy may be contraindicated. Mood disorders wtih ADHD plus ODD/CD responded best to a combination of behavioral therapy and medication treatment.
ADHD with Mood Disorders
The researchers noted that ADHD with mood disorders responded much better to treatment than clients with just ADHD or clients with ADHD and ODD/CD. In some ways, comorbid mood disorders may have offered ameliorating effects on ADHD; thus, predicting better outcomes for these individuals.
In the study described above, 579 children were randomly selected from a clinical population and assigned to different treatment groups: meds, behavioral, combination of both, and community comparison. Treatment lasted 14 months. All children were previously diagnosed with ADHD, combined type. Other diagnoses were not considered and not children were excluded for having another diagnosis. Average age was 8.2 years. The researchers administered various tests to evaluate for each of Cantwell’s criteria (see above). Afterwards, multivariate analysis was used to evaluate the data, as well as treatment effects.
As described above, different subgroups responded differently to treatment. This has implications when providing treatment for clients with ADHD. Having a thorough understanding of the symptoms experienced by clients, will help clinicians make better choices when choosing treatment options. For example, it may be important to know when medication is most effective and behavioral treatment is less effective.
Other disorders which are more common in those with ADHD than in the general population, include disruptive mood dysregulation disorder, major depressive disorder, and anxiety disorders. According to the DSM-5, most children who meet criteria for disruptive mood dysregulation disorder will also meet criteria for ADHD. Although a minority of people with ADHD meet criteria for major depressive disorder and anxiety disorders, these disorders are more common in individuals with ADHD than the general population (American Psychiatric Association, 2013).
