Scientists still do not fully understand what causes many brain tumours. Researchers have identified some recognised risk factors, but no single factor explains every diagnosis. This guide explains what scientists know so far, what remains, and why that distinction matters. Only 3% of brain tumours in the UK are related to external factors, meaning most of them aren’t preventable.
Do we know what causes brain tumours?
No single definitive cause of primary brain tumours has been identified.
Scientists still cannot fully explain why many brain tumours develop. They have identified some recognised risk factors, such as certain genetic conditions and radiotherapy to the head, but they have not found one clear explanation that applies to every diagnosis.
A cause tells you why something happened. A risk factor only means something may increase the chance of it happening. It does not mean a brain tumour will develop, and it does not mean doctors will always find one clear reason behind every diagnosis.
What risk factors have researchers identified?
Several factors may affect brain tumour risk.
These include:
- Age
- Some inherited genetic conditions
- Previous exposure to radiation, particularly to the head/neck
- A small number of environmental factors still under investigation
The evidence is stronger for some of these factors than for others. Scientists can identify patterns, but they still cannot explain every diagnosis.
Why do recognised risk factors still leave so many unanswered questions?
Recognised risk factors do not give researchers a complete explanation for every diagnosis. They show that some patterns exist, but they do not show one clear path that explains why every brain tumour develops. A person may have a recognised risk factor and never develop a brain tumour. Another person may receive a diagnosis without any obvious known risk factor in their history.
This is one reason the subject remains difficult to explain in simple terms. Brain tumours include many different tumour types, and those tumours do not all follow the same biological pattern. A factor that may affect risk in one situation may not help explain another. That is why discussion of brain tumour causes has to stay cautious.
Does age affect the risk of brain tumours?
Yes, age does affect risk. While brain tumours can affect anyone at any age, the number of people diagnosed with a brain tumour increases significantly with age. The average number of brain tumour cases per year are highest in those aged 70-74. (Source: CRUK: Brain, other CNS and intracranial tumours incidence statistics).
There are certain brain tumour types that predominantly affect children, teenagers and young adults. These include medulloblastoma, DIPG and other paediatric-type diffuse high-grade gliomas.
Can inherited conditions increase risk?
Some inherited conditions can increase the risk of developing a brain tumour.
Inherited genetic conditions account for a small proportion of brain tumours. These include conditions such as NF2, tuberous sclerosis, Li-Fraumeni syndrome, Turcot syndrome and von Hippel-Lindau syndrome.
Most brain tumours are not caused by inherited genetic conditions. Inherited conditions account for only a minority of diagnoses.
What about radiation and environmental factors?
The best established environmental risk factor for brain tumours is exposure to radiation. Previous radiotherapy to the head for the treatment of another cancer is known to increase the risk of certain types of brain tumour such as gliomas, meningiomas and sarcomas.
Certain hormonal contraceptives and treatments have also been linked to an increased risk of a certain type of brain tumour known as meningioma.
Other risk factors such as pesticides, industrial chemicals, viruses and diet, have been studied, but the evidence remains less certain.
Extensive studies have shown no link between brain tumour and mobile phone usage.
Why do researchers stay careful when they talk about causes?
Researchers stay careful because the strength of the evidence is not the same in every area. Some links are better established than others. Previous exposure to radiation is the clearest environmental risk factor identified so far. Other areas, such as pesticides, industrial chemicals, viruses and diet, have all been studied, but the evidence remains less certain.
That difference matters. Careful language helps separate stronger evidence from areas that still need more research.
In addition, for some risk factors, the benefit of their use outweighs the risk they carry for some patients at the time of decision making, i.e., radiotherapy treatment for certain cancers. However, everyone’s situation is different, and the risk needs to be discussed and understood by individual patient.
(Extensive studies have shown no link between brain tumour and mobile phone usage.
Why do brain tumour causes remain so uncertain?
Major gaps in understanding still remain.
Brain tumours are not one disease. They include many different brain tumour types, each with its own biology, behaviour and pattern of development. That makes it harder to identify one simple explanation for why a tumour develops.
Research has identified some risk factors, but scientists still do not have one complete explanation.
Why does research into causes still matter?
Research into causes matters because uncertainty still shapes the whole field.
If scientists can understand more about why brain tumours develop, they can also improve how they classify tumours, investigate risk, and develop better treatments over time. The fact that there is still no single definitive cause shows why long-term research remains essential.
Across its Centres of Excellence, Brain Tumour Research funds long-term research to improve understanding and treatment for brain tumours. You can read more in Our Research Strategy. That research reflects the charity’s wider mission to move closer to a cure for all types of brain tumours.
Since records began in 2002, the UK has directed just 1% of national cancer research spending towards brain tumours. Brain Tumour Research is the only national charity focused on finding a cure for all types of brain tumours.
If you want to support that work, you can donate, fundraise, campaign, or help raise awareness of the need for sustained investment in brain tumour research.
Medical disclaimer
Use this information for general awareness and educational purposes only. It does not constitute medical advice. If you have concerns about your health, contact your GP or a qualified medical professional for advice and assessment.
References used
Brain Tumour Research. Brain Tumour Causes. https://braintumourresearch.org/pages/information-brain-tumour-causes
Brain Tumour Research. Our Vision, Mission and Values. https://braintumourresearch.org/pages/our-vision-mission-and-values
Brain Tumour Research. Centres of Excellence. https://braintumourresearch.org/pages/information-centres-of-excellence
Brain Tumour Research. What are Brain Tumours. https://braintumourresearch.org/pages/information-what-are-brain-tumours
Brain Tumour Research. Brain Tumour Types. https://braintumourresearch.org/blogs/information/brain-tumour-types
Brain Tumour Research. Brain Tumour Facts. https://braintumourresearch.org/pages/brain-tumour-facts
Brain Tumour Research. Our Research Strategy. https://braintumourresearch.org/pages/our-research-strategy