Prozac link to brain tumours

A new study has found evidence of a possible link between the popular anti-depressant Prozac and brain cancer.

Researchers have discovered that the drug, taken as a "happiness pill" by millions of people around the world, could stimulate tumour growth by blocking natural defences against cancer cells.

The study, carried out by an international team of scientists led by John Gordon, professor of immunology at Birmingham University, found that cancerous cells can be killed by "positive thinking" - a natural defence mechanism which could be damaged by taking Prozac.

The researchers studied the effects of Prozac and other antidepressants on tumour cells growing in a test tube. They found that the drug interfered with serotonin levels in the brain and stopped cancer cells from " selfdestructing", causing tumours to grow at a faster rate than usual.

The findings are likely to lead to calls for a re-evaluation of the long-term effects of the drug, which was first introduced in the US in 1987 and has since become widely used for the treatment of depression, bulimia and obsessive-compulsive disorder.

Professor Gordon, whose study will be published in the journal Blood next week, stressed that his team's results could not be taken as proof that taking Prozac directly stimulates the growth of tumours.

He said: "Although that extrapolation could be valid, there is no direct evidence from large-scale epidemiological studies to back it up. However, it's important that we look at it again."

Explaining his research, which looked into new ways of treating blood cancer, Professor Gordon said he had looked at how the brain communicates with the immune system to encourage "positive thinking" through the production of serotonin.

He told The Independent: " Serotonin is a natural chemical that regulates people's moods, keeping them balanced. Too much serotonin affects appetite and sleep and too little affects the mood - often causing depression.

"An exciting property of serotonin is that it can tell some cells to self-destruct. We have found that serotonin can get inside the lymphoma cells and instruct them to commit suicide, thereby providing the potential for an effective therapy."

Prozac, which works by blocking serotonin from being quickly reabsorbed by the brain's nerve cells, had the effect of stimulating the growth of a type of tumour known as Burkitt's lymphoma. Other, similar drugs such as Paxil and Celexa had the same effect.

Eli Lilly, the company which manufactures Prozac, said the research was too new for a detailed response. A spokeswoman said: "It's not something we can comment on because we haven't been involved in it."