Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by inattention, hyperactivity and impulsivity. It often begins in childhood and can persist into adulthood. ADHD is associated with several other conditions and diseases, both physical and mental. Understanding these comorbidities is important for proper diagnosis and management of ADHD.
What is ADHD?
ADHD is considered a disorder of executive functioning. It affects parts of the brain that control attention, concentration and impulses. There are three main presentations of ADHD:
- Predominantly inattentive – difficulty sustaining attention, easily distracted, forgetful
- Predominantly hyperactive/impulsive – fidgety behavior, excessive talking, difficulty waiting turns
- Combined type – symptoms of both inattention and hyperactivity/impulsivity
ADHD often begins in childhood and the symptoms can vary over time. It is estimated that ADHD affects around 5% of children and 2.5% of adults worldwide. The exact causes are unknown but research suggests genetics, environmental factors and brain chemistry and structure play a role.
Comorbidities
Comorbidity refers to the presence of two or more disorders or illnesses occurring at the same time. ADHD has one of the highest rates of comorbidity of any psychiatric disorder. Up to 8 in 10 people with ADHD may have at least one additional mental or physical condition.
Some of the more common comorbidities include:
- Learning disabilities – 35%
- Oppositional defiant disorder – 35%
- Conduct disorder – 25%
- Anxiety disorders – 25%
- Depression – 15% to 20%
- Bipolar disorder – 15% to 20%
- Substance use disorders – 15% to 25%
There are also strong associations with certain physical health conditions like epilepsy, sleep disorders and obesity. Let’s look at some of the major comorbidities associated with ADHD in more detail:
Learning Disabilities
Up to 35-40% of people with ADHD also have specific learning disabilities. The most common being:
Dyslexia
Dyslexia causes difficulties with reading and writing. People with dyslexia often struggle with:
- Reading fluency and accuracy
- Spelling and writing ability
- Phonological processing – manipulating language sounds
- Verbal working memory
Research suggests that ADHD and dyslexia share some common genetic risk factors and brain abnormalities. The combination of ADHD and dyslexia can make focusing on reading very difficult.
Dyscalculia
Dyscalculia causes difficulties with math skills and understanding mathematical concepts. Common symptoms include:
- Difficulty memorizing and recalling math facts
- Understanding time, direction and sequence
- Aligning numbers to solve math problems
- Number sense and estimation
Studies show that people with ADHD are significantly more likely to have dyscalculia compared to the general population. Issues with working memory and executive functioning associated with ADHD can make mathematical reasoning very challenging.
Dysgraphia
Dysgraphia causes difficulties with handwriting and fine motor skills. People with dysgraphia may have:
- Illegible and inconsistent handwriting
- Problems holding and controlling a pencil
- Issues with spatial planning on paper
- Difficulty organizing thoughts on paper
Research indicates that ADHD and dysgraphia often co-occur, although the exact reasons are still unclear. Issues with dexterity and executive functioning associated with ADHD likely play a role.
Mental Health Disorders
ADHD has strong associations with a wide range of mental health conditions:
Anxiety Disorders
Up to 25% of people with ADHD also have an anxiety disorder such as:
- Generalized anxiety disorder
- Social anxiety
- Separation anxiety
- Specific phobias
It is believed that poor emotional regulation and impulsivity associated with ADHD may predispose individuals to anxiety disorders. The combination of ADHD and anxiety can be highly impairing.
Depression
Estimates suggest 15% to 20% of people with ADHD also suffer from depression. Symptoms like low energy, poor concentration and low self-esteem may overlap between the two conditions. Research indicates that ADHD could be an independent risk factor for developing depression later in life.
Bipolar Disorder
Studies show up to 20% of adults with ADHD may also have bipolar disorder. Both conditions involve issues with emotional dysregulation and impulse control. ADHD symptoms can often look like a mild form of mania in bipolar disorder. The co-occurrence is associated with greater illness severity and impairment.
Oppositional Defiant Disorder
Around 35% of children with ADHD also have oppositional defiant disorder (ODD). ODD involves frequent and persistent anger, irritability, arguing and defiance towards authority figures. The combination of ADHD and ODD can severely disrupt a child’s schooling and home life.
Conduct Disorder
Estimates suggest 25% to 30% of children with ADHD also have conduct disorder – a condition characterized by antisocial behavior like aggression, destruction of property, deceitfulness and rule breaking. The impulsivity and behavioral disinhibition of ADHD likely contributes to the development of conduct disorder.
Substance Use Disorders
ADHD has a strong association with substance abuse and addiction. Up to 25% of adults with ADHD struggle with drug or alcohol dependence. It is believed that some individuals use substances to self-medicate their symptoms. The impulsivity and risk taking behaviors associated with ADHD are also risk factors for developing a substance use disorder.
Physical Health Conditions
In addition to mental health disorders, ADHD is linked to a number of physical health conditions:
Sleep Disorders
Studies indicate around 25% to 50% of people with ADHD have sleep disturbances like:
- Insomnia
- Delayed sleep phase syndrome
- Restless leg syndrome
- Sleep disordered breathing
The inattention and hyperactivity of ADHD can make settling down to sleep very difficult. ADHD medications may also disrupt sleep patterns in some cases.
Epilepsy
Epilepsy is a neurological disorder characterized by seizures. Research shows that:
- Around 5% of children with ADHD also have epilepsy
- Children with ADHD and epilepsy tend to have more learning difficulties
- ADHD and epilepsy share some similar brain abnormalities
Medications used to treat ADHD may lower seizure thresholds in some patients with epilepsy.
Obesity
Studies consistently show links between ADHD and obesity:
- Children with ADHD are twice as likely to be obese
- Around 55% of adults with ADHD are obese
- ADHD symptoms like impulsivity may contribute to overeating
- Some ADHD medications may affect metabolism and weight
The combination of ADHD and obesity is associated with greater impairment in day-to-day functioning.
Other Conditions
There are connections between ADHD and other health conditions like:
- Asthma – share some genetic risk factors
- Sensory processing disorder – difficulty processing sensory input
- Tics/Tourette Syndrome – chronic motor or vocal tics
- Gut issues – altered gut microbiome associated with ADHD
More research is needed to determine the nature of these associations with ADHD.
Summary of Major Diseases/Disorders Associated with ADHD
| Type | Condition | Prevalence |
|---|---|---|
| Learning Disabilities | Dyslexia | 20-30% |
| Dyscalculia | 10-15% | |
| Dysgraphia | 15-20% | |
| Mental Disorders | Anxiety Disorders | 25-30% |
| Depression | 15-20% | |
| Bipolar Disorder | 15-20% | |
| Oppositional Defiant Disorder | 35-40% in children | |
| Conduct Disorder | 25-30% in children | |
| Substance Use Disorders | 15-25% in adults | |
| Physical Conditions | Sleep Disorders | 25-50% |
| Epilepsy | 5% in children | |
| Obesity | 55% in adults |
Diagnosing Comorbid Conditions
Given the high rates of comorbidity, experts recommend screening all individuals diagnosed with ADHD for:
- Learning disabilities – psychoeducational testing
- Mental health disorders – interviews, symptom rating scales
- Neurological conditions – medical history, physical exam
- Substance abuse – questionnaires, toxicology testing
Identifying co-occurring conditions is important for developing optimal treatment strategies. The right interventions and supports can improve overall prognosis and quality of life for people with ADHD and comorbidities.
Treatment Considerations
Managing ADHD and comorbid conditions presents certain challenges including:
- Complex medication regimens – balancing efficacy and side effects
- Higher healthcare costs and use of services
- Poor coordination between multiple providers
- Adherence issues due to polypharmacy
A multidisciplinary approach involving psychotherapy, medications, educational interventions, skills training and lifestyle changes tailored to the individual’s needs is recommended.
Some key treatment strategies include:
- Cognitive behavioral therapy for ADHD and co-occurring mental health issues
- Social skills training and behavioral management for ADHD with ODD/CD
- Specialized educational plans (IEPs) for ADHD with learning disabilities
- Sleep hygiene techniques for ADHD with sleep disorders
- Nutrition counseling and physical activity for ADHD with obesity
Treatment plans should be continuously monitored and adjusted based on efficacy and tolerability. Overall, a patient-centered approach that addresses the multifactorial nature of ADHD with comorbidities can lead to positive outcomes.
Conclusion
ADHD frequently co-occurs with a diverse range of other medical and psychiatric conditions. Learning disabilities, mental health disorders like anxiety and depression, and physical health issues like sleep disturbances and epilepsy are more common in people with ADHD compared to the general population.
Careful screening and a multimodal treatment approach that considers ADHD and its comorbidities together is key to effective management. Ongoing research and a better understanding of the genetic and neurological factors linking ADHD to various comorbid disorders will help guide more targeted and personalized interventions in the future.