Differential Diagnosis of ADHD/ADD* in Children and Adults Research Informed Assessment
By Carrie Jaffe, Ph.D.
ADHD is a neurobehavioral disorder that usually appears in early childhood before the age of 7. It is characterized by varying degrees of inattention, hyperactivity/impulsivity, and impairments in executive functioning, such as self-regulation, motivation, effort, processing speed, cognitive flexibility, organization, and planning. The prevalence of ADHD is estimated to be between 3-10% of school-aged children. Between 50-80% of them meet criteria for ADHD in adulthood; it is estimated that between 1.5-8% of the adult population has ADHD.
However, the symptoms of a variety of other medical, psychiatric, and developmental disorders, as well as environmental and social stressors frequently mimic the symptoms of ADHD in both children and adults. Thus, these statistics may be inaccurate. This article illustrates the importance of conducting a comprehensive, rather than focused assessment in order to rule out other frequently occurring causes of presenting symptoms.
ADHD is often diagnosed via clinical interview that consists of a thorough history of academic, development, and behavioral functioning, as well as a series of symptom-focused questions related to the DSM-IV diagnosis of ADHD. Occasionally, an astute clinician conducts a Continuous Performance Test (CPT), which is a standardized computer test of attention disorders. When the developmental history and symptoms are found to be consistent with the DSM-IV diagnostic criteria, the diagnosis is often made at that time. Although a comprehensive clinical interview is the cornerstone of diagnosing ADHD, formal psychological/ neuropsychological testing is recommended to rule out other frequently occurring causes of the symptom pattern.
In fact, the American Academy of Pediatrics (AAP) Guidelines recommend that the assessment of ADHD include a thorough evaluation of co-existing conditions, because as many as half of the children diagnosed with ADHD also have a co-existing condition. It is essential to assess the contribution of other factors as either a primary cause or secondary response to ADHD. For example, according to the AAP, research on ADHD and a thyroid disorder called Generalized Resistance to Thyroid Hormone (GRTH) indicates that a high percentage of children with GRTH are diagnosed with ADHD. Similarly, research findings indicate that cognitive response patterns similar to those of people diagnosed with ADHD have been reported in patients with other disorders that affect the frontal lobes, such as Non-Verbal Learning Disability (NVLD). Indeed, there is a high frequency of incorrect ADHD diagnoses in people found to actually have NVLD.
Conditions that mimic or co-occur with ADHD include, but are not limited to the following:
- Hearing or vision problems
- Syndromes such as Fetal Alcohol Syndrome (FAS), Fragile X, etc.
- Generalized Resistance to Thyroid Hormone (GRTH)
- Normal aging in adults
- Conduct Disorder or Oppositional Defiant Disorder (Prevalent among approximately ¼- 1/3 of children diagnosed with ADHD.)
- Mood Disorders (Depression, Bipolar Mood Disorder) (Prevalent among approximately 1/5 of children diagnosed with ADHD.)
- Anxiety Disorders (Prevalent among approximately ¼ of children diagnosed with ADHD.)
- Substance-Related Disorders
- Pro Dromal Psychosis
- Poor self-esteem
- Family dysfunction
- Physical/psychological/sexual abuse or neglect
- Post Traumatic Stress Disorder
- Learning Disabilities (Prevalent among 12-50% of children with ADHD)
- Language Disorder
- Mental Retardation
- Non-Verbal Learning Disability
- Pervasive Developmental Disorders (Autism, Asperger’s Disorder, Pervasive Developmental Disorder Not Otherwise Specified)
Unfortunately, these conditions are often missed or misdiagnosed when the diagnosis of ADHD is made based solely on a CPT and clinical interview, no matter how comprehensive. Thus, it is crucial to rule out co-occurring disorders and disorders that mimic ADHD by including behavior rating scales and formal psychological/neuropsychological testing in the evaluation process. According to Mapou (2009), a comprehensive assessment of ADHD should include the following:
- Comprehensive clinical interview to include complete developmental, academic, behavioral, and symptom history
- Referral to a physician for a complete physical exam
- Assessment of intelligence and academic achievement
- Assessment of attention and memory
- Assessment of learning
- Assessment of executive functioning
Accurate Assessments of San Diego specializes in Psychological, Developmental, Educational, and Substance Abuse Evaluations that target issues uniquely relevant to each individual. We are committed to a Standard of Excellence that values best- practices techniques and the use of well-validated instruments.
* In this article, “ADHD” encompasses all types of this diagnosis, including Attention Deficit Disorder, Hyperactive Type, Attention Deficit Disorder, Inattentive Type, and Attention Deficit Disorder, Combined Type.
Mapou, Robert L. (2009). Adult Learning Disabilities and ADHD: Research Informed Assessment. Oxford University Press
Leslie, Laurel K. (2008). About ADHD. Retrieved November 23, 2011, from https://research.tufts-nemc.org/help4kids