This is a big question, and a critical one. Proper treatment rests upon the accuracy of the diagnosis. When making a diagnosis, the practitioner must evaluate each symptom and its possible causes. Because different disorders share similar symptoms, the diagnostician must decide which diagnosis best explains the symptom set.
There are several alternative diagnoses that could cause symptoms similar to ADHD. These similar disorders with symptoms similar to ADHD are:
- Normal age-appropriate behavior;
- Low IQ or High IQ (intelligence measurement);
- Oppositional defiant disorder;
- Disruptive mood dysregulation disorder;
- Anxiety disorders;
- Mood disorders;
- Personality disorders;
- Substance-related and addictive disorders; and,
- Dissociative disorders
- Medical conditions that cause inattention and impulsivity (e.g., hyperthyroidism, hearing and vision problems).
That quite a list! Let's review it in more detail.
Young children may display signs of restless activity, impulsivity, and inattention simply as a result of their young age. At certain ages, these behaviors are considered normal age-appropriate behavior. This possibility has to be considered as an option in the evaluation.
When children with low-IQ are placed in educational settings that exceed their abilities, they may respond by day-dreaming, not paying attention, or acting out. This may look similar to ADHD but their treatments are quite different. A child with low-IQ may also have ADHD. Likewise, when gifted children (high IQ) are placed in environments that are under-stimulating they may respond in a similar manner: boredom, disinterest, and restlessness.
There is an entire category of disorders that can mimic symptoms of ADHD. This group of disorders is called, Disruptive, Impulse-Control, and Conduct Disorders. One of the most notorious disorders in the group is called oppositional defiant disorder. While the symptoms may look similar to ADHD, the two disorders are quite different. For example, suppose there is a child who refuses to do homework. An ADHD student's refusal may be because they don't want to experience failure again. In contrast, a student with oppositional behavior might do this out of defiance, and opposition to rules. It is possible to have both disorders. Many ADHD individuals develop oppositional behavior secondary to ADHD.
Another disorder is called disruptive mood dysregulation disorder (DMDD). Individuals with DMDD have frequent and severe temper outbursts of an intensity that greatly exceeds the situation that prompted it. These outbursts can result in injuries to the child and those around them. Children with DMDD display a steadily irritable and angry mood between outbursts that is observable to others. These children may also display hyperactive, impulsive, and inattentive behaviors that could easily be mistaken for ADHD. However, DMDD irritability looks quite different than ADHD. The DMDD irritability includes more severe temper outbursts and constant irritable mood. Until now there was not a clear method to distinguish between the two.
Some children may have both conditions. Therefore, it is critical that the correct diagnosis be identified in order to establish an effective treatment plan.
There are several other diagnoses that might also cause ADHD like symptoms. These include mood disorders, anxiety disorders, substance-related and addictive disorders, dissociative disorders, or a personality disorder. The symptoms of these disorders usually appear later in life than do the ADHD symptoms. However, ADHD individuals may develop mood or anxiety disorders secondarily to ADHD. In other words, problems and challenges created by ADHD can be discouraging to the point that some individuals become extremely anxious or depressed. The root causes and specific conditions that contribute to various symptoms must be examined and sorted through in order to arrive at an accurate diagnosis.