ADHD Causes: A Practical Guide for Australians

Possible causes of ADHD

The Australian ADHD Guideline describes ADHD as multifactorial, and the sources list several factors rather than one cause.

• Genes: the Australian ADHD Guideline states ADHD is highly heritable in children and adults, at an estimated 70-80%.
• Genetic studies: a genome-wide association meta-analysis identified 12 independent genomic loci that increase susceptibility to ADHD.
• Pregnancy and birth: healthdirect says maternal smoking or drinking during pregnancy, premature birth and low birth weight may contribute.
• Environment: healthdirect lists lead exposure and early childhood trauma as factors that may contribute.

The healthdirect ADHD page gives a plain-language summary of ADHD causes.

Biological causes of ADHD and what causes ADHD disorder

The biology is still being studied, and the guideline describes it as multifactorial rather than caused by one thing.

Our guide to the ADHD brain explores how people experience attention, energy and focus.

Are you born with ADHD or does it develop? ADHD causes over time

The evidence points to genes playing a large part, and it also points to environmental factors that may contribute.

• The guideline states ADHD is highly heritable, with an estimated heritability of 70-80%.
• healthdirect says genetic studies show ADHD is an inherited disorder.
• Environmental factors such as premature birth, low birth weight, lead exposure and early childhood trauma may contribute, according to healthdirect.
• Whether ADHD was noticed early or later is a different question from where it comes from, so ask your clinician about the person’s history.

Is ADHD something you are born with?

Genes play a large part: the guideline estimates heritability at 70-80%, and healthdirect says genetic studies show ADHD is an inherited disorder.

• Genes are a major factor, and nobody chooses their genes.
• Ask your clinician about family history, since it can help them understand the individual picture.
• If you are thinking about what causes autism, keep in mind that autism and ADHD are different conditions.

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ADHD chemical imbalance: what the guideline says

“Chemical imbalance” is a popular phrase, and the guideline’s wording is more specific.

• The Australian ADHD Guideline describes ADHD as a multifactorial disorder, so it is not presented as one chemical fault.
• It notes that methylphenidate, which is used to treat ADHD, raises extracellular levels of dopamine and noradrenaline.
• Questions about medicines belong with your GP, paediatrician, psychiatrist or pharmacist, who can explain options for the individual.
• Never start, stop, change or share a medicine without medical advice.

How do people get ADHD, and why does it happen?

The research looks at inherited and environmental influences, and the steps below show how to start a conversation with a clinician.

1. 1Look at family history. Ask relatives whether anyone has an ADHD diagnosis, because heritability is estimated at 70-80%.
2. 2Note pregnancy and birth details. Maternal smoking or drinking during pregnancy, premature birth and low birth weight are factors healthdirect says may contribute.
3. 3Think about early life. Lead exposure and early childhood trauma are also listed by healthdirect as factors that may contribute.
4. 4Share it with a clinician. Your GP, paediatrician or psychiatrist can put the pieces together.

Reading about how many people have ADHD may help: around 6-8% of children and 3-5% of adults in Australia have ADHD, which means more than 1 million Australians, according to the guideline’s GP factsheet.

Does ADHD cause overthinking or IBS?

A clinician is the right person to look at these questions for an individual, rather than a general guide.

• If you notice overthinking, a clinician can help work out whether it relates to ADHD, anxiety or something else.
• Gut symptoms, including those linked with IBS, should be checked by your GP.
• Keep a short diary of what you notice and when, and take it to your appointment.
• Do not assume a symptom is caused by ADHD without a proper assessment.

When to talk to a GP or specialist

You do not need to know the cause before you ask for help.

• You or your child often struggle to focus, stay organised or manage energy in ways that affect daily life.
• Teachers, employers or family members have raised concerns about attention or impulsivity.
• ADHD runs in your family and you want to understand what that means.
• You are unsure whether feelings such as overthinking or gut symptoms are linked to ADHD.
• You want to understand what support, assessment and funding might be available.

Call 000 in an emergency. The healthdirect helpline on 1800 022 222 is staffed by registered nurses 24 hours a day, and the ADHD Foundation is on 1300 39 39 19.

TQN Care support workers help with personal care, community access, respite and help around the home across Sydney, Melbourne and surrounding areas (NSW & VIC). Tell us what you need and we will call you back.

Your next step

Understanding where ADHD comes from can help, though what matters most is the support that fits your day. TQN Care offers practical NDIS support services such as personal care, community access, respite and help around the home across Sydney, Melbourne and surrounding areas (NSW & VIC). We support daily life, not treatment. Make a referral and we will talk through what you need.