Millions taking one of UK’s most common medications could be protected from cancer, study suggests

Taking antidepressants could help the body fight off cancer, a study has suggested.

Experts found a type of antidepressant taken by millions of patients each year could help shrink tumours by more than 50 per cent.  

Antidepressants are typically taken for mood disorders as the drug is thought to interfere with the chemical serotonin—the brain’s ‘happiness hormone’.

But the study sought to explore if this process could also influence other parts of the body, including the systems that help to prevent tumours developing.

The researchers, who published their findings in the journal Cell, were inspired after finding cells from some tumours had high levels of molecules that break down serotonin.

So, they sought to explore if using an antidepressant called selective serotonin reuptake inhibitors (SSRIs), which blocks this process, could help the body naturally kill tumours.

They tested the drug in mice with cancerous tumours, as well as human cancer cells in petri dishes.

They found SSRI treatment reduced average tumour size by half by making the body’s cancer-fighting proteins more effective at killing mutated cells.

Dr Lili Yang, of the University of California and senior author of the new study, said: ‘It turns out SSRIs don’t just make our brains happier, they also make our T cells [the body’s fighter cells] happier.

‘SSRIs increase T cells’ access to serotonin signals, reinvigorating them to fight and kill cancer.’

Dr Yang added that as SSRIs have been used safely for years, ‘repurposing’ them for cancer treatment is much easier, and faster than developing a new drug. 

The researchers also found the medication boosted the effectiveness of existing cancer therapies.

They tested a combination of an SSRI and a treatment called anti-PD-1 antibody in mice with cancer. 

This antibody therapy works by blocking signals that surpress the immune system, therefore allowing fighter cells to attack tumours more effectively. 

By adding an SSRIs, researchers significantly reduced tumour size in all treated mice and even achieved complete remission in some cases.

An obvious limitation of the study acknowledged by the authors is that their findings are based on lab tests or animal experiments, not real patients.

However, the team is now planning a new research project in which they will examine real world data from cancer patients taking antidepressants. 

They estimate about a fifth of cancer patients are coincidentally also taking SSRIs, presenting an opportunity to explore if they have a better outcome than patients not taking the drug. 

While the study suggested SSRIs could one day be used to help treat cancer, others have linked their long term usage to health problems.  

Previous studies have linked their use to  long-term and even permanent sexual dysfunction.

Health service figures show antidepressants are one of the most commonly taken medications in the UK.

Official data suggests as 8.7 million people in England were prescribed the medication—about 15 per cent of the total population.

In the US an estimated one in eight people are currently taking an antidepressant, according to the Centers for Disease Control.  

More than 400,000 people are diagnosed with cancer each year in the UK, according to Macmillan Cancer Support.