When two or more disorders occur at the same time, they are called co-occurring disorders (or co-morbidity). In general, individuals affected by ADHD often have other behavioral disorders that impact their ability to function successfully. About 60-80% of the time, someone with ADHD will also have another disorder (CHADD, n.d.). Likewise, about 25% of all children with ADHD also have a mood, depressive, or anxiety disorder (CHADD, n.d.).
The high comorbidity rate between ADHD and other disorders has created confusion regarding the definition of a "true" ADHD diagnosis. Since most children or adults with ADHD also have a second diagnosis, and both sets of symptoms frequently overlap, critics suggest that the nuances of ADHD have not been adequately described. Some even suggest that making an early ADHD diagnosis is inappropriate (i.e., when a child is very young). For instance, with very young children, it may not be possible to determine whether their symptoms will become ADHD, early onset Bipolar Disorder, or some other disorder. Each situation requires careful observation and evaluation to distinguish between various explanations for problematic behaviors. Obviously, establishing an accurate ADHD diagnosis is very challenging for even the most experienced clinicians!
When someone has two or more disorders, the treatment process can become very complex. For instance, medication treatment might be managed differently if a person has another diagnosis in addition to ADHD. People with ADHD also develop problems regulating their emotions in response to their disorder. This may lead to the development of additional problems and another diagnosis. Lastly, research indicates that individuals with ADHD, (both children and adults) are often impacted by the consequences of their own actions. For instance, increased risk-taking, substance abuse, and criminal behavior often have lasting consequences.
When other disorders are present, it can make the diagnosis of ADHD much more difficult to pinpoint and the symptoms harder to treat. Some comorbid disorders that commonly occur alongside ADHD are:
- Oppositional Defiant Disorder
- Conduct Disorder
- Bipolar Disorder
- Learning Disorder
- Sensory Integration Disorder
- Early Speech/Communication problems
ADHD and Oppositional Defiant Disorder
Oppositional Defiant Disorder (ODD) symptoms occur in as many as 21% to 60% of children with ADHD. ODD symptoms tend to occur more often around people familiar to the child, such as family or caregivers. Some of the behaviors associated with Oppositional Defiant Disorder include:
- Arguing with adults or refusing to comply with rules;
- Frequently periods of anger, resentfulness, or vindictiveness;
- Deliberately annoying others, and/or becoming easily annoyed with others; and,
- Blaming others for mistakes.
Oppositional defiance to authority generally begins to appear well before adolescence and can indicate a true case of ODD. It could also be a side effect of a child's frustration with the world around him. Tensions flare in response to what the child with ADHD sees as "unreasonable" demands. This frustration can then trigger angry refusals. However, it is encouraging to note that children with ODD do improve.
ADHD and Conduct Disorder
Conduct Disorder involves some serious behaviors that usually get people into trouble. The behavioral symptoms include:
- Repeated aggression towards people (including fighting) or animals;
- destruction of property;
- deceitfulness or theft; and,
- serious violations of rules (e.g., running away from home, or skipping school).
There are some similarities between ADHD and Conduct Disorder. However, they can be distinguished from each other. Those with a single diagnosis of ADHD may get into trouble for lying or skipping school, but generally they are not aggressive. Likewise, the degree of problem behavior is not as intense and blatant as is the behavior of those with conduct disorder. However, some individuals may meet the diagnostic criteria for both diagnoses. Research indicates that as many as 25% to 40% of children with hyperactive-impulsive type ADHD also meet the criteria for a Conduct Disorder. The rate of conduct disorder in those ADHD children without hyperactivity is significantly lower.