The causes of non-Hodgkin lymphoma

For most people with NHL, a cause is never found. But there are factors that are known to increase the risk of developing NHL, which we’ve listed below.

However, most people who develop NHL don’t have any of these.

A weakened immune system

If the immune system doesn’t work fully the risk of developing lymphoma is higher. Some conditions reduce immunity, such as HIV. People taking medicines to weaken (suppress) their immune system after an organ transplant also have a higher risk.

Autoimmune disease

Autoimmune diseases develop when the immune system attacks healthy body tissue by mistake. Several autoimmune disorders can increase the risk of developing NHL. These include rheumatoid arthritis, Sjogren’s syndrome (which causes dry eyes and dry mouth), and Hashimoto’s thyroiditis (which causes inflammation of the thyroid gland).

Doctors don’t fully understand why these disorders increase the risk of developing NHL. It may be due to the effects of the autoimmune condition. It may also be because some treatments for autoimmune conditions suppress the immune system. Or it may be due to a combination of these things.

Previous cancer treatment

NHL is slightly more common in people who have been treated for cancer before. Treatment with radiotherapy, or with some chemotherapy drugs, can increase a person’s risk of developing NHL many years later. However, the risk is very small compared to the benefit of having the treatment in the first place.


Some viruses or bacteria can increase the risk of developing NHL. A stomach infection called helicobacter pylori can sometimes cause a type of NHL to develop in the stomach. This is called MALT lymphoma.

The Epstein Barr virus (EBV), which causes glandular fever, may slightly increase the risk of developing NHL. However, EBV is very common in the UK and very few people go on to develop NHL because of it. The risk of causing NHL is highest in people who are having long-term treatment to suppress their immune system after an organ transplant.

Having a close relative with NHL

People who have a close relative (a parent, brother or sister) with NHL have a slightly increased risk of developing it themselves. But their risk of developing NHL is still low, with a lifetime risk of about 3 in 100 (3%).