Autism spectrum disorder (ASD) can often come with other conditions. This is called ‘comorbidity’. Some of the conditions that can occur with ASD cause more difficulty than others. Most can be treated. 

Comorbidity and autism spectrum disorder

Nearly three-quarters of children with autism spectrum disorder (ASD) also have another medical or psychiatric condition. This is called ‘comorbidity’, and the conditions are often called ‘comorbid’ conditions.

Comorbid conditions can appear at any time during a child’s development. Some might not appear until later in adolescence or adulthood. Sometimes these comorbid conditions have symptoms that affect how well ASD therapies and interventions work. So it’s important to identify the conditions and treat them separately.

Here are some of the common comorbid conditions that might be diagnosed in children with ASD.


People with anxiety have a range of symptoms including tension, restlessness, hyperactivity, worry and fear. For children with ASD, anxiety might show up as self-stimulating more often, asking questions over and over again, hurting themselves, or having trouble getting to sleep.

How common is anxiety in children with autism spectrum disorder?

Anxiety is common among people with ASD. Up to 84% of people with ASD have anxiety symptoms.

Anxiety can happen at any age, but older children and those with less severe ASD are more likely to be anxious.

Social anxiety is one of the most common anxiety disorders. Social anxiety probably happens because people with ASD often have social difficulties that can make them feel stressed and anxious. Obsessive compulsive disorder is also a common anxiety disorder.

How is anxiety treated?

Medication, behaviour therapy, cognitive behaviour therapy and relaxation techniques can all be used to treat anxiety.

You might like to read more about anxiety in children with autism spectrum disorder.

Attention deficit hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) can cause children to act before they think, and have trouble focusing and sitting still. Generally all three behaviours happen together, but some children can be mainly inattentive.

Many children have trouble with sitting still and focusing. But in children with ADHD, this behaviour is extreme and has a big impact on children’s daily life.

How common is ADHD in children with autism spectrum disorder?

ASD and ADHD share some common characteristics like not seeming to listen when people speak, interrupting, or intruding on other people’s personal space. Up to two-thirds of children with ASD have behaviour that’s very similar to ADHD.

How is ADHD treated?

There’s no cure, but you can manage ADHD using behaviour strategies, medication, or a combination of the two.

You might like to read more about Attention deficit hyperactivity disorder (ADHD).

Bipolar disorder

Bipolar disorder is a psychiatric condition. People with bipolar disorder have both extreme emotional highs (mania) and extreme lows (depression).

The depression can be quite obvious – the person will probably have low mood, lack of motivation, trouble sleeping and poor appetite. Mania can be harder to spot. Its symptoms include extreme self-esteem, less need for sleep, and being more talkative and active than usual.

Children who have bipolar disorder have big and quick changes in mood and behaviour. When they’re going through these mood changes, they might also have trouble paying attention, sitting still and behaving appropriately.

How common is bipolar disorder in children with autism spectrum disorder?

There isn’t a lot of research into bipolar disorder and ASD, but one study suggests that bipolar disorder might be fairly common among children with ASD. This study found that 27% of teenagers and young adults with less severe ASD who were referred to an outpatient clinic met the diagnostic criteria for bipolar disorder.

How is bipolar disorder treated?

Treatment is usually long term. It often involves medication. There are some behaviour treatments that work.

Clinical depression

Symptoms of depression include low mood, poor sleep and appetite, irritability and a loss of motivation. In children depression symptoms can also be cranky moods rather than just sadness and low moods.

How common is depression in children with autism spectrum disorder?

Depression is common among people with ASD, especially among higher-functioning people who know they have social difficulties.

Symptoms of depression have also been associated with more severe characteristics of ASD, older age and higher verbal IQ.

How is depression treated?

Health professionals often use a combination of medication and psychotherapy, like cognitive behaviour therapy, to treat depression.

How well treatment works depends on several things, including the person’s optimism, control over things that cause stress and experience with other treatments. It also depends on how long the person has had depression and how much support the person gets from family and friends.

Down syndrome

Down syndrome is a genetic disorder.

Most people have 23 pairs of chromosomes. People with down syndrome (also called Trisomy 21) have an extra 21st chromosome. This causes characteristic facial features, developmental delays, poor muscle tone, potential hearing and vision problems and congenital heart defects.

Down syndrome can be identified with tests during pregnancy. If it isn’t picked up then, it’s usually diagnosed at birth or in early infancy.

How common is down syndrome in children with autism spectrum disorder?

Studies have shown that up to 17% of people with ASD have down syndrome.

How is down syndrome treated?

Down syndrome can’t be cured. The health problems associated with down syndrome can be treated, usually very well.

Fragile X syndrome

Fragile X is a genetic disorder. It’s the most common cause of inherited intellectual disability.

Most boys with this condition have an intellectual disability, sometimes severe. In the early years this would be noticed as developmental delay. In girls the condition generally looks like a learning disability rather than intellectual impairment. Children with the condition have trouble communicating.

How common is fragile X in children with autism spectrum disorder?

Although ASD is relatively common in children with fragile X (25-33%), fragile X happens much less frequently than ASD. This means that only about 2% of people with ASD also have fragile X.

How is fragile X treated? 

There’s no cure for fragile X. Treatment usually involves medication, early intervention and educational support.

Gastrointestinal symptoms

The most common gastrointestinal symptoms for people with ASD are chronic constipation, abdominal pain, diarrhoea and faecal incontinence. Other problems can include gastro-oesophageal reflux disease (GORD) and bloating of the abdomen.

Gastrointestinal symptoms have been linked with more severe ASD and behaviour problems. It’s not clear why children with ASD have relatively high rates of gastrointestinal symptoms, but it might be because of altered gut bacteria, increased gut permeability, longer food transit time through the gut, or low fibre intake.

How common are gastrointestinal symptoms in children with autism spectrum disorder? 

Between 9% and 70% of children with ASD have gastrointestinal problems.

How are gastrointestinal symptoms treated?

Because there are many reasons why a child might have gastrointestinal symptoms, the child will need a thorough medical examination before starting any treatment.

There’s no evidence to support the general use of a gluten-free or casein-free diet. But like some typically developing children, children with ASD might have gluten intolerance, or other food sensitivities, allergies or intolerances. If this is the case, specific diets can help.

Immune disorders

There are many different types of immune disorders.

An immune disorder is when a person’s body overreacts to a substance – for example, a harmless foreign substance found in the environment, in the case of allergies. An autoimmune disorder happens when a person’s immune system mistakenly attacks the person’s own body tissues.

Autoimmune diseases – for example, type-1 diabetes and rheumatoid arthritis – develop when antibodies that normally fight infectious organisms instead attack the body itself.

Immune disorders have many different symptoms. Some of the most common symptoms include fatigue, weakness, itchy skin, dizziness, ill-feeling and fever.

How common are immune disorders in children with autism spectrum disorder?

Immunological factors might play a role in the development of autism spectrum disorder (ASD) in some cases. Many children with ASD have a family history of autoimmune diseases.

Also, many children with ASD suffer from recurring viral infections. ASD happens more frequently in association with certain viral infections like rubella.

How are immune disorders treated?

Immune disorders can’t be cured, but they can be managed through anti-inflammatory drugs, physical therapy and pain killer medication.

Intellectual disability

Intellectual disability can be diagnosed when a child six years or older has an IQ below 70 as well as difficulties with daily tasks. In children under six years, the term ‘developmental delay’ is used for children with significant cognitive and language delays.

Intellectual disability varies from person to person. Children with autism spectrum disorder (ASD) and intellectual disability might have uneven skills, so there are some things that they’re quite good at and others they find hard.

In most cases, children with ASD have more trouble with verbal skills – like talking, listening and understanding – than with non-verbal skills like doing puzzles or drawing.

How common is intellectual disability in children with autism spectrum disorder?

Intellectual disability is common among children with ASD – 50-60% of people with ASD have an IQ below 70.

How is intellectual disability treated?

There might be significant improvements over time in some very young children with ASD who have developmental delay. But most children who have developmental delay might still have a lower than typical IQ when they’re older.

There’s no cure for intellectual disability, but it can be managed so that many people can live a reasonably normal life. Early intervention and education can support people with intellectual disability and their families.

Macrocephaly and microcephaly

Macrocephaly and microcephaly are conditions in which a person’s head is much bigger (macrocephaly) or smaller (microcephaly) than average.

The conditions can be present from birth or can show up during a child’s development.

Both conditions might be a symptom of abnormal brain development. Children with macrocephaly might be completely healthy, or might have an underlying medical condition. Children with microcephaly usually have smaller heads because of a medical condition and generally have intellectual disability.

How common are macrocephaly and microcephaly in children with autism spectrum disorder? 

About 20% of children with ASD also have macrocephaly, although reported rates vary from 0% to 34%. We don’t know how common microcephaly is, but it’s more common in children with ASD who also have intellectual disability and other genetic conditions related to ASD.

How are macrocephaly and microcephaly treated?

Many children with macrocephaly are otherwise healthy. But macrocephaly can also happen because of another medical condition. In this case, that underlying medical condition is treated.

For children with microcephaly, treatment generally focuses on managing symptoms and giving children support for their learning and educational needs.

Obsessive compulsive disorder (OCD)

Obsessive compulsive disorder (OCD) is a type of anxiety disorder.

People with OCD have thoughts that they don’t want but can’t get out of their heads. They behave in repetitive and compulsive ways to deal with these thoughts. For example, they might wash their hands over and over again, or arrange or count objects in patterns, as a way of cancelling out bad thoughts with good thoughts.

How common is OCD in children with autism spectrum disorder?

OCD is common among people with ASD. People with ASD also tend to have repetitive thoughts and behaviour. Because restricted and repetitive behaviour is more common in younger children with ASD, OCD seems to be more common at younger ages.

How is OCD treated?

OCD can be treated with behaviour therapy, cognitive therapy, medications or any combination of the three.

Seizures and epilepsy

Epilepsy is when a person has two or more attacks of abnormal electrical activity in the brain.

The nerve cells of the brain release uncontrolled and unpredictable electrical charges and cause odd sensations and abnormal movement or behaviour. These are called convulsions or seizures. When a person has a seizure, there’s usually a temporary period of unconsciousness, a body convulsion, unusual movements or staring spells.

It can be hard to spot epilepsy in children with ASD because seizure symptoms can be like some ASD characteristics, like failing to respond to your name or doing repetitive, tic-like behaviour.

How common are seizures and epilepsy in children with autism spectrum disorder?

Epilepsy is quite common, and 20-30% of people with ASD also have epilepsy. Seizures are most common in children under five years and in teenagers.

People with ASD and moderate to severe intellectual disability, people with ASD and other neurological conditions (for example, cerebral palsy), or children who show regression are more likely to develop epilepsy.

There might also be a genetic relationship between seizures and ASD.

How are seizures and epilepsy treated? 

Treatment usually involves anti-epileptic medication. There are some steps you can take to minimise the effects of epilepsy. These include making sure your child takes medication on time, gets enough good-quality sleep and avoids situations that cause stress.

Sensory sensitivities

Signs of sensory sensitivities include:

  • avoiding certain textures, tastes, sounds and smells

  • eating a limited diet

  • preferring to be naked or being rigid about clothing

  • placing hands over ears.

How common are sensory sensitivities in children with autism spectrum disorder? 

Up to 76% of young children with ASD might have sensory sensitivities. This is because many children with ASD experience the world very differently from typically developing children. Their brains process information from the senses differently. They can be extremely sensitive or insensitive to touch, sight, smell, taste, sound, pain or temperature.

The most common sensory sensitivities are overreactivity to sound and underreactivity to pain. The least common sensitivity is to smell.

Children with sleep problems, self-harming behaviour or tantrums might be more likely to have sensory sensitivities.

Sensory sensitivities aren’t related to IQ.

How are sensory sensitivities treated?

There’s no cure for sensory sensitivities, but you can reduce unpleasant sensory stimulation for your child. For example, you could avoid buying certain clothing fabrics that your child doesn’t like. If you can’t avoid an unpleasant sensory stimulation, you can use behaviour strategies to help your child gradually accept the stimulation.

Sleep problems

The most common sleep problems in children are insomnias – that is, trouble falling asleep and staying asleep – and parasomnias, which include nightmares, night terrors and sleepwalking.

How common are sleep problems in children with autism spectrum disorder?

Sleep difficulties are common among children with ASD. About two-thirds of children with ASD might have a sleep problem at some time.

How are sleep problems treated?

Good sleep hygiene can help. This can include:

  • cutting out drinks with caffeine in the afternoon and evening

  • getting sunshine and exercise throughout the day

  • getting rid of distractions like computers from the bedroom

  • having a regular bedtime routine.

You should always use these strategies at the same time as any other intervention.

Behaviour interventions can help, particularly for settling and night waking. Medication is another option, but health professionals generally recommend this only if behaviour interventions have failed. Melatonin is the only medication currently thought to be helpful.

You might like to read more about
Promoting good sleep habits for children with ASD and Dealing with sleep difficulties in children with ASD.

Tourette syndrome

Tourette syndrome is an inherited brain disorder. People with tourette have many movement-based tics and one or more vocal tics. These tics are sudden, repetitive and involuntary.

How common is tourette syndrome in children with autism spectrum disorder?

Tourette syndrome is common among people with ASD.

One study found that 11% of children and teenagers with ASD had tourette syndrome (vocal tics and motor tics) and a further 11% had motor tics. Tourette syndrome or motor tics are more common in those with moderate to severe intellectual disability.

How is tourette syndrome treated?

Treatment for tourette syndrome involves helping the person with the condition manage the tics. Psychobehavioural therapy, education, medication and reassurance can all help.

Tuberous sclerosis

Tuberous sclerosis is a genetic disorder that causes abnormal growths in the brain and other vital organs. Symptoms can include white patches on the skin, facial rash, seizures, behaviour difficulties like hyperactivity, and intellectual disability.

How common is tuberous sclerosis in children with autism spectrum disorder?

Tuberous sclerosis is not that common among children with ASD (0-4%). It’s more common if the person also has a seizure disorder (8-14%).

How is tuberous sclerosis treated?

There’s no cure for tuberous sclerosis. Treatment focuses on managing symptoms and supporting the person and family.

Getting help

If you think your child has another condition as well as ASD, talk with a health professional like your child’s General Practitioner (GP), family doctor or pediatrician. Depending on the condition, the professional might be able to order some tests, including a genetic test, or refer you to a specialist for further assessment.

© raisingchildren.net.au, translated and adapted with permission

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