Attention Deficit Hyperactivity Disorder and Anxiety

Introduction

A high comorbidity for attention deficit hyperactivity disorder (ADHD) and anxiety has been reported in epidemiologic studies and clinical psychiatric ADHD and pediatric samples.

This comorbidity is not innocuous but confers greater executive functional deficits, greater social difficulties, and poorer quality of life (QoL) and precedes later substance use. Despite the significant impairments, there is limited knowledge on the underlying neurobiology and treatment management for the combination.

Background

The cooccurrence of ADHD and anxiety disorders is common in the pediatric population. Comorbid anxiety disorders are reported to occur in 30%–40% in clinical psychiatric samples of children with ADHD and pediatric samples. Epidemiologic studies also report high comorbid rates of 25% in the general population, suggesting that the comorbidity is not due to referral bias that might be expected in clinical samples. The comorbidity is bidirectional with high levels of ADHD (16%–24%) reported in children with anxiety.

The comorbidity has significant impact because children with ADHD and comorbid anxiety disorders have greater attention, cognitive, and executive functioning difficulties than children with ADHD alone, as well as greater social difficulties. Sciberras and colleagues observed that children with multiple anxiety comorbidities (two or more) had poorer parent-reported QoL, more behavioral problems, poor peer interactions, and impaired daily functioning. Such poor functioning is not observed in children with single anxiety comorbidity, thus indicating that only the high and pervasive level of anxiety is associated with functional impairment. In addition, such high levels of anxiety may lead to avoidance and negative thought patterns that may negatively influence the functioning. ADHD and anxiety disorders also precede later substance use.

Prevalence

Data on the prevalence of comorbidity between ADHD and anxiety disorders are derived from both epidemiologic and clinical studies in children and adolescents. Clinical studies have limitations, as they recruit individuals from specialty treatment settings with more severe symptomatology and more impairment and those who come from families experiencing increased burden from their children’s problems.

Summarized in Table 3.1 are the epidemiologic studies in children and adolescents that used standardized evaluations and reported the rate of comorbidities between ADHD and anxiety disorders to determine the joint odds ratio for the pairs of disorders.

Summarized in Table 3.2 are the representative clinical studies showing the prevalence of anxiety in children and adolescents with ADHD. Overall, results from both the epidemiologic and clinical studies indicate that the rates of comorbidity between ADHD and anxiety disorders occur at the rate of 25% with variations depending on age, gender, severity, and number of comorbidities.

The multimodal treatment ADHD (MTA) study found that the prevalence of anxiety disorders in a sample of 579 children with ADHD between the ages 7.0–9.9 years was 33.5%. Studies have observed that a variety of anxiety disorders, including separation anxiety disorder, generalized anxiety disorder, overanxious disorder, posttraumatic stress disorder, panic disorder, and agoraphobia, occur in association with ADHD. One study assessing the comorbidity in preschool-aged children with ADHD found a similar rate of anxiety disorders in preschool children with a trend toward multiple comorbidities. The occurrence of one anxiety disorder should therefore merit careful screening for other anxiety disorders.

Age and Development

Children with ADHD and anxiety are older in age at the time of presentation than children with ADHD alone. Although comorbid anxiety disorders are seen in one-fourth (25%) of children with ADHD, they increase to one-third (33%) in adolescent age group and even higher in adults. In the National Comorbidity Survey Replication study (NCS-R), 47.7% of adults with ADHD had a comorbid anxiety disorder within the last 12 months.

Increased rates of anxiety disorders have also been reported in clinical samples that were followed longitudinally as seen in Table 3.2 . Biederman and colleagues also noted that the nature of these comorbid anxiety diagnoses in ADHD may change over time. Children with ADHD who progressed to have anxiety disorders in adulthood were more likely to present with simple phobias in their preschool years. They had high rates of separation anxiety and social anxiety disorders on entering school age and high rates of generalized anxiety disorder in adolescence. A 4-year follow-up study found that children with multiple anxiety disorders at baseline had significantly increased risk of agoraphobia, social phobia, and separation anxiety. Studies in adults with ADHD have found high rates of comorbid generalized anxiety, social phobia, specific phobias, and posttraumatic stress disorders. In part, the high rates in adults may be explained by increased help-seeking and self-referral for treatment in adults.

In a longitudinal twin study, Agnew-Blais and colleagues investigated childhood risk factors and young adult functioning of individuals with persistent, remitted, and late-onset ADHD. At age 18 years, individuals with persistent ADHD had more impairment at school or work, socially, higher levels of generalized anxiety disorder, marijuana dependence, and conduct disorder (CD) compared with those whose ADHD had remitted.

Gender

A review study from the Massachusetts General Hospital examining the gender effects on ADHD and comorbid anxiety found that girls with ADHD had greater prevalence of simple phobia, agoraphobia, and panic disorder compared with boys with ADHD. There also appears to be some gender difference in the rate of multiple comorbid anxiety disorders, which is about 33% in girls compared with 28% in boys.

Pliszka has examined the nature of impulsivity in children with ADHD and comorbid anxiety and found that the group as a whole was inattentive but not impulsive on the continuous performance test (CPT). Newcorn and colleagues reported high levels of impulsivity as rated by CPT that was irrespective of comorbidity except in ADHD girls who had lower levels.

In a large-scale prospective longitudinal study that included 170 ADHD children compared with 88 non-ADHD controls, Smith and colleagues noted that preschool hyperactivity was a strong predictor of poor adolescent/adult outcomes for males and less for females.

In one study using a dimensional measure of anxiety that examined the covariation of both of these symptoms cross-sectionally and over a 1-year follow-up the investigators noted that ADHD symptoms are associated with elevated physical anxiety symptoms and social and separation anxiety. These symptoms were linked with inattention and were pronounced in girls but not in boys. The study found no evidence that ADHD predicted the onset of anxiety symptoms or vice versa over a year of follow-up.

Screening

There are several rating scales that are commonly used to screen for symptoms of ADHD and anxiety. The advantages of these tools include being economical, readily available, and easy to administer. The Vanderbilt ADHD Teacher (VADTRS) and Parent Rating Scales (VADPRS) are straightforward instruments that follow DSM-IV criteria for ADHD and include 12 criteria for Conduct Disorder and 7 criteria from the Pediatric Behavior Scale, which screen for anxiety and depression in children aged 6–12 years. Both versions of the Vanderbilt ADHD Rating Scale have been validated and shown to be statistically significant instruments. The VADTRS and VADPRS are in the public domain and available widely free of charge.

ADHD measures can be generally grouped into broadband and narrowband instruments. Examples of broadband measures, which contain probes of both externalizing and internalizing disorders, include the Child Behavior Checklist (CBCL) and the Devereux Scales of Mental Disorders (DSMD). Although helpful for identifying cooccurring conditions, they are lengthier making them perhaps clinically less useful over time.

ADHD-specific measures, or narrowband measures, include only questions related to ADHD. Examples include the Conners Rating Scale (CPRS) ; the Barkley’s School Situations Questionnaire (SSQ-O-I); the Swanson, Nolan and Pelham Questionnaire (SNAP) ; the ADHD Rating Scale-IV ; and the ADHD Symptoms Rating Scale.

In one review that sought to differentiate youth who had been referred for evaluation of ADHD from those who were not referred, using the CBCL (teacher and parent forms), DSMD, and CPRS (teacher and parent forms), Green and colleagues found an average effect size of 1.5 across broadband measures. In contrast, the ADHD-specific measures were found to be more beneficial in distinguishing youth with ADHD with the Conners’ scale having the highest effect sizes (3.1–3.7) and the SSQ-O-I having the lowest (1.3).

Diagnosis

It is important for clinicians to assess for ADHD and anxiety as part of any comprehensive medical or mental health assessment. A thorough clinical assessment includes separate interviews with the parent and child. Self-reporting should not be relied on for either ADHD or anxiety symptoms. Also, Pliszka noted that about half of the children who met criteria for overanxious disorder by their own self-report are not rated as anxious by their parents, indicating that parents may be unaware of their children’s internalizing symptoms. Children who met criteria for comorbid anxiety by self-report were also reported to have lower levels of self-confidence and more impairment in daily functioning compared with parent-reported anxiety. Corroborating information from teachers is also very helpful.

The Diagnostic and Statistical Manual of Mental Disorders , Fifth Edition ( DSM-5 ) can be helpful in delineating criteria that are helpful in arriving at a diagnosis. For ADHD, one must establish a sufficient number of core symptoms and functional impairment in at least two settings. This is based on behavioral observations made by parents and teachers, which can be reported through behavior rating scales. It is important to note that parent and teacher reports of ADHD symptoms do not always align. In a study of 74 children, 55 youth met criteria for DSM-IV ADHD, based on either parent or teacher interviews; however, parents and teachers only agreed in 17 of these cases, with parents endorsing the diagnosis almost twice as often as teachers. Furthermore, as elementary school teachers typically spend the majority of the day with children in one classroom, they may more accurately report symptoms of ADHD as compared with secondary school teachers who typically only see youth for one period a day. In fact, high-school teachers have shown little agreement with other raters on symptoms of ADHD.

Observation of ADHD symptoms by the clinician in the office can be helpful but is not necessary for a diagnosis, as only 20% of patients show hyperactivity in novel settings, such as the clinic. On the other hand, observation during the clinical interview is extremely helpful in identifying anxiety.

Structured interviews, such as the Diagnostic Interview Schedule for Children ( http://www.columbia.edu/cu/csswp/journal/newsfall94/cdisc.html ), the Diagnostic Interview for Children and Adolescents (DICA), and the Kiddie Schedule for Affective Disorder and Schizophrenia (K-SADS), are often not only used in research studies but can also be extremely useful in the clinical setting. Additionally, the Anxiety Disorders Interview Schedule for children, child, and parent versions (ADIS) is a semistructured diagnostic interview that has been shown to be valid in assessing all DSM-IV anxiety disorders, as well as ADHD in children aged 6–17 years. In a study examining interrater agreement on diagnoses using the ADIS, the level of agreement was determined to be excellent between raters for primary diagnosis (κ = 0.92) and individual anxiety disorders (κ = 0.80–1.0).

Clinical Workup

As summarized in Table 3.3 , the clinical workup for the comorbid ADHD and anxiety disorders should include a medical history and physical examination. The medical history that includes a thorough review of systems is essential in ruling out visual, auditory, respiratory, cardiovascular, and neurologic factors. The history will also help identify medications (e.g., sympathomimetics used to treat asthma) that may contribute to the ADHD or anxiety symptoms, as well as substance use.

Although there are no specific physical or neurologic findings for either ADHD or anxiety disorder, listening for cardiac murmurs may be important for anxiety disorders such as panic disorder. Obtaining baseline measures of height and weight is important in identifying growth delays. Cardiovascular parameters such as blood pressure (BP) and heart rate (HR) and electrocardiogram are important especially if medications are considered. There are no laboratory studies specific for ADHD or anxiety; it is important to identify anemia, low serum ferritin and lead levels. A baseline comprehensive metabolic panel is important in checking blood glucose and calcium, as well as obtaining baseline liver function if medication treatment is considered. Although abnormalities in thyroid functioning can have effects on children’s mood and behavior, studies do not support the regular evaluation of thyroid functioning when screening for ADHD.

Assessing sleep is very important. Mayes and colleagues have noted that children with ADHD and comorbid anxiety or depression have significant sleep problems such as difficulty falling asleep, restlessness during sleep, waking during the night, nightmares, walking or talking in sleep, waking too early, and sleeping less than normal in the subgroups with anxiety/depression versus without anxiety or depression (e.g., ADHD-I plus anxiety/depression vs. ADHD-I alone). These sleep difficulties are comparable to those in children with just anxiety or depressive disorders but are more prevalent in children with just ADHD. Polysomnography may need to be considered in children who snore and are restless during sleep.

When staring spells are present that are not attributed to inattention, an EEG may be necessary to investigate absence seizures and simple partial epilepsy.