Diagnostic Challenge 2: ADHD versus Similar Disorders

Diagnostic Challenge #2: Teasing ADHD apart from other similar disorders (differential diagnosis and co-occurring disorders):

ADHD has symptoms in common with other disorders. This is called symptom overlap. Symptom overlap occurs with many physical and mental conditions. For instance, a runny nose could mean an allergy, a cold, a flu, illegal drug use, or a side effect of some treatment- just to name a few. Therefore, a clinician must determine which diagnosis best explains a set of presenting symptoms. This is called making a differential diagnosis.

To make things even more complex, someone may have two or more similar disorders (with overlapping symptoms). Sometimes, one disorder might lead to another and vice versa (e.g., depression and alcoholism). When a person has two or more diagnoses, this is called comorbidity, or co-occurring disorders. In fact, ADHD rarely occurs alone. Research has shown that more than two-thirds of people with ADHD have one or more co-occurring conditions. According to Weitzen, the National Comorbidity Survey Replication Study (2006) found that "individuals diagnosed with depression, bipolar disorder, or anxiety disorders, showed corresponding ADHD rates of 32%, 21%, and 9.5% in a community survey. Between 17- 45% of adults with ADHD have alcohol abuse or dependence problems."

Since many symptoms of ADHD overlap with other disorders, it is important to consider these other diagnoses as possible co-occurring disorders, in addition to ADHD. Or, perhaps the correct primary disorder (instead of ADHD) is one of these other options. In this case, the clinician would need to discriminate between two possible disorders and determine which one is actually present. Taking the time to differentially diagnose an individual is critical in designing an effective treatment plan. The following disorders could occur along with ADHD or be an ADHD look-alike. This list is illustrative and not all-inclusive. Always consult your health care provider about any diagnostic or treatment concerns. Carefully consider all medical advice.

Hyperactivity/Impulsivity Type ADHD may look similar to:

• Oppositional defiant disorder
• Intermittent explosive disorder
• Specific learning disorder
• Disruptive mood dysregulation disorder
• Bipolar disorder
• Personality disorders
• Substance use disorders
• Anxiety disorders
• Post-traumatic event symptoms/disorder (PTSD)
• Sleep disturbance
• *Other neurological or developmental problems: psychosis or neurocognitive disorders
• *Other medical problems: TBI, lead poisoning, medication side-effects, or malnourishment
• *Other drug effects

Inattention Type ADHD may look similar to:

• Specific learning disorder, and/or an executive functioning disorder
• Autism spectrum disorder
• Intellectual disability
• Reactive attachment disorder
• Depressive disorder
• Personality disorders
• Substance use disorders
• Anxiety disorders
• Post-traumatic event symptoms/disorder (PTSD)
• Sleep disturbance
• *Other neurological or developmental problems: psychosis or neurocognitive disorders
• *Other medical problems: TBI, lead poisoning, medication side-effects, or malnourishment
• *Other drug effects

Combined Presentation Type may share similarities with all the above-mentioned disorders.

*Other neurological, developmental, and medical disorders can generate symptoms that may look like ADHD. Likewise, a wide range of legal and illegal drugs can cause ADHD-like symptoms. For instance, neurological disorders such as learning disorders, (problems learning math, reading, writing, or language) or intellectual disabilities, can all result in hyperactivity, distractibility, and poor ability to focus. Other medical issues such as diabetes or hypoglycemia, thyroid problems, lead exposure, or even medication side-effects can all create various problems that appear similar to ADHD symptoms. Substance use disorders can limit effective planning and decision-making while increasing impulsivity and acting-out behaviors. Sleep disturbances can drastically interfere with cognitive function.

A skillful clinician, particularly one with that specializes in adult ADHD, is very familiar with these other similar conditions. The clinician will sort out whether there are co-existing conditions in addition to ADHD; or, whether another similar diagnosis might better explain the symptoms. In either case, it is essential that all are diagnosed and treated together. As you can see, sorting through symptoms and associated causes can be a lengthy and complicated process. That's why we emphasize the importance of seeking a highly-qualified professional. Ideally this would include specialization in adult ADHD.

Traumatic Brain Injury and ADHD

Traumatic Brain Injury (TBI) occurs when the brain is damaged or harmed as occurs in accidents and battlefields. Its symptoms are like ADHD symptoms. These include memory problems; impulsivity; poor emotional regulation; and, personality changes. However, there are some distinctions. In TBI, the memory problems are sudden and recent, occurring shortly after the injury. The problems of memory for people with ADHD are not sudden, nor recent. In ADHD, the memory problems are the result of inattention and poor concentration (not due to injury) and must be present before 12 years of age.

For people with TBI, academic skills may be affected. Those with ADHD may also experience gaps in learning. However, this is largely due to poor attention and concentration. Depending upon the location of the injury, the brain damage of a TBI can negatively impact behavior. Behavioral patterns may include aggression and hyperactivity. However, unlike ADHD, these negative behaviors may be resistant to behavioral modification strategies. In contrast, those with ADHD affected by aggression and hyperactivity, typically respond well to behavior modification techniques.

Socially, those with TBI may become more self-centered. Naturally, this self-focus interferes with social relationships and they may lose friends. Once again, the change will occur or increase rather suddenly, post-injury. People with ADHD have similar problems with their social relationships. Their poor social skills threaten their friendships. This is usually due to impulsivity; difficulty with planning and meeting commitments; and, the lack of attention to social interactions. Unlike people with TBI (who experience a sudden onset of social problems post-injury), the social problems for those with ADHD have been present since childhood.

Finally, brain injury may cause unpredictable mood swings. These mood swings could be confused with ADHD symptoms. For TBI-affected individuals, emotions often do not match the situation in terms of intensity, or expression (e.g. laughing when sad). In contrast, those with ADHD often have difficulty managing and expressing feelings, and may have more depression than their peers. However, their emotions are clearly related to the events that precipitated them. Nonetheless, many of these emotional differences are subtle and are difficult to tease out.

Specific Learning Disorder (formerly Learning Disability) and ADHD

Specific Learning Disorder (LD) refers to problems with learning (reading, math, and writing). Individuals with LDs usually have varying learning abilities across different subject areas. In contrast, those with ADHD demonstrate consistent learning problems across most subject areas; particularly those they find uninteresting or dull.

LDs are thought to result from impaired information-processing. However, this impairment is different from the information-processing problems in ADHD. For people with ADHD, information-processing is not a problem in itself. Instead, information-processing problems stem from impulsivity and inattention, which subsequently interferes with information-processing. It may seem like splitting hairs, but to clinicians, these distinctions point to different treatment approaches. The success of treatment largely depends upon the right approach.

Those with LDs may learn more slowly. However, once information is learned, it is generally well remembered. In contrast, those with ADHD have learning interruptions due to inattention and poor concentration. As such, they may be unable to recall portions of previously learned material.

The social skills of those with specific learning disorder may be affected. However, individuals generally manage to interact effectively with others. In contrast, the social skills of those with ADHD are affected by impulsivity and poor attention to others. Social relationships suffer as a result.

Emotionally, those with learning disabilities may be prone to sudden outbursts during stressful situations. In contrast, those with ADHD tend to be hyperactive, and often depressed. Although many differences between individuals with these two disorders exist, these subtle differences are challenging to identify. Teasing them apart requires experience and significant time.