Autism vs. ADHD: What Are the Differences?

Attention deficit hyperactivity disorder (ADHD) and autism are both neurodevelopmental disorders, and they have several symptoms in common. For example, people with autism and ADHD may both be impulsive, and people with both disorders may develop speech later than is typical in children.

ADHD and autism, however, are distinct diagnoses. It's entirely possible to have both ADHD and autism. When that happens (which it does quite often), it's important to recognize and treat both disorders appropriately.

This article explores how autism and ADHD are similar to and different from one another in their symptoms, causes, diagnosis, and treatment.

Symptoms of Autism and ADHD

Both autism and ADHD are described as neurodevelopmental disorders in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).

The descriptions of the two disorders don't overlap at any point, so it would be reasonable to conclude that they are entirely different from one another. In fact, until 2013, it was not permissible to diagnose both autism and ADHD in the same person.

In 2013, however, dual diagnoses became an accepted practice—and the number of people with dual diagnoses grew. The Centers for Disease Control and Prevention (CDC) notes that about 14% of children with ADHD also have autism diagnoses (though some estimates are much higher). More than half of children with autism may have symptoms of ADHD.

While the symptoms of ADHD and autism may not look the same on paper, they can look very similar in person.

Traits like distractibility and impulsivity, for example, are part of the ADHD diagnosis. While they're not part of the autism diagnosis, they appear in most people with autism. Speech delays and idiosyncrasies are part of the autism spectrum disorder (ASD) diagnosis and not the ADHD diagnosis. Yet, people with ADHD often have speech delays.

Both ADHD and autism are usually diagnosed in childhood, and symptoms are likely to continue throughout patients' lives.

Symptoms That ADHD and Autism Have in Common

The reality is that many people diagnosed with either ADHD or autism have overlapping or similar symptoms. In addition, people with both disorders can have difficulties that may not be listed as traditional symptoms but that can impact daily life.

Here are some of the symptoms and challenges that people with ADHD and autism often share:

• Impulsivity: Including speaking out of turn and jumping up when it's inappropriate
• Lack of focus: In ADHD, typically being distracted by external events, and in autism, being distracted by your own thoughts and ideas
• Problems with executive functioning: Difficulties in the ability to organize time, tasks, and projects
• Challenges with social interaction and making friends
• Learning differences and disabilities
• Sensory challenges: Over- or under-responsiveness to light, sound, touch
• Emotional immaturity: Difficulty in managing anger and frustration

It's important to note that these symptoms, while they look similar, may result from different causes. For example, social challenges in autism may result from a lack of imitative speech or body language skills. By contrast, social challenges in ADHD may result from impulsivity, taking control, or an inability to conform to group expectations.

Causes

Researchers are still in the process of figuring out what causes autism and ADHD. There is no doubt that both ADHD and autism are heritable, meaning that they run in families. That means there is a genetic component to both disorders. There are also some environmental issues that can lead to autism, ADHD, or both.

Researchers are currently exploring how differences in brain structure and chemistry may cause autism, ADHD, and other developmental disorders.

Causes of ADHD

Besides genetics, risk factors for ADHD include:

• Brain injury
• Exposure to environmental risks (such as lead in paint) by a parent during pregnancy or in the person at a young age
• Alcohol and tobacco use by a parent during pregnancy
• Premature delivery
• Low birth weight

Causes of Autism

All of the risk factors of ADHD except brain injury are also risk factors for autism. In addition, autism may be caused by specific genetic developmental disorders such as fragile X syndrome and by fetal exposure to specific drugs (valproic acid and thalidomide). Older parents are also more likely to have children with autism, but the reasons for this are not clear.

Diagnosis

There are no medical tests for either ADHD or autism. Diagnosis for both relies on observations, interviews, and assessments of development and behavior. Prior to making an autism or ADHD diagnosis, practitioners conduct tests and ask questions to rule out other possible contributions to attentional issues such as anxiety or a learning disability.

In most cases, autism and ADHD are diagnosed in young children. The process starts when a pediatrician screens a child for symptoms by asking a series of questions about the child's development and behavior. If the screening suggests further testing is necessary, the pediatrician will recommend a full evaluation.

Both autism and ADHD, particularly when mild, may be diagnosed in adults. Usually, the diagnosis comes from a psychologist or psychiatrist, though it may also come from a general practitioner.

Evaluation for autism or ADHD is often conducted by a team of specialists. Some specialties represented may include:

• Developmental pediatricians
• Child psychologists and/or child psychiatrists
• Neuropsychologists
• Speech-language pathologists
• Occupational therapists

At the evaluation, specialists use a variety of different tests to determine the child's intelligence quotient (IQ), speech and language skills, and behaviors. They also ask parents a number of questions about the child's development. They also may ask parents to fill out questionnaires about their child's behaviors, growth, medical history, and more.

Treatment

While the diagnosis and causes of autism and ADHD may be similar, treatments are usually quite different. In part, that's because there are pharmaceutical treatments for ADHD while there are none that directly treat autism.

It's also important to note that autism, unlike ADHD, is a spectrum disorder. That means that there are people with both mild and severe autism—and severe autism can be extremely disabling.

Treatments for Autism

There is a wide range of treatments for autism, depending on the individual's particular needs. The most common, however, include:

• Pharmaceuticals: Medications can help with specific symptoms such as anxiety.
• Behavioral therapy: This therapy can build specific skills and reduce negative behaviors such as breakdowns in self-control.
• Speech therapy: Some people with autism have severe speech delays or no spoken language at all, while others have difficulty with conversational and social speech.
• Occupational therapy: Many people with autism have fine-motor difficulties and/or sensory challenges that make it hard to be around bright lights and loud noises.
• Social skills therapy: Most people with autism need help to learn how to interact socially, build friendships, and manage emotions.

Treatments for ADHD

Most people with ADHD are treated, at least partially, with pharmaceuticals to help decrease impulsivity and increase focus. These medications may be stimulants or non-stimulants, and the choice of treatment may depend on the age of the patient. In addition, treatments may include:

• Skills training
• Counseling
• Behavioral therapy, since behaviors related to ADHD are somewhat different from those related to autism but can also cause serious problems in school or at work

Summary

ADHD and autism are not the same disorder, but they may be hard to tell apart. In addition, it's very common for one individual to have both diagnoses. Treatment for the two disorders is similar but not identical, so it's important to get the correct diagnosis or diagnosis.

Both disorders typically are diagnosed in childhood by pediatric psychologists, developmental pediatricians, or other specialists. Adults may be diagnosed by a primary healthcare provider, psychologist, or psychiatrist.