Tamoxifen and impaired cognitive function

Can I take a moment to point out that it’s not my fault that my brain exists in a hazy fog?

Tamoxifen can contribute to impaired cognitive function.

One of the groups I follow on facebook is a breast cancer support group and this information is a summary of a post initiating a discussion on the cognitive impact of tamoxifen.  The information was gathered from a number of scientific research papers.

Detrimental cognitive side effects of tamoxifen:

  • processing speed
  • executive function
  • verbal memory

Other side effects:

  • joint pain
  • sexual disfunction
  • risk of uterine cancer
  • cardiovascular morbidity

How does Tamoxifen work to prevent cancer?

Tamoxifen inhibits the absorption of eostrogen to cells which prevents or slows growth of breast cancer types which are ‘fed’ by this hormone.

How does Tamoxifen affect the brain?

Brain cells need estrogen for healthy cognitive functioning.
Evidence shows that frontal and temporal structures of the brain are affected most, with these areas used in everyday memory, executive functions that enable us to inhibit distracting stuff, switch between tasks as and when we need to, and update information in working memory.
Tamoxifen has also been known to interrupt the process of neurogenesis which is the brain’s ability to form new neural connections in the brain and re-generate itself.

What’s the evidence?

A meta-analysis summarising the effects of lots of published studies, supports the damaging effect of Tamoxifen on the brain.  This is seen in both post and pre-menopausal women.  AIs (aromatase inhibitors), an alternative to Tamixifen, have a similar effect, though it seems they have less of an impact than Tamoxifen.

The long term effects of Tamoxifen are unknown, there are reports that suggest cognitive function can improve over time, however this is not substantiated.


From my own perspective, I certainly experience impairment to cognitive function which is most likely caused by Tamoxifen.  Yes, it can be incredibly frustrating and definitley has an impact on my life but having been on Tamoxifen for 3.5 years I simply accept these problems as my new normal.  I don’t always like it but it is what it is.

While it’s tempting to suggest a short term break to my oncologist, just in the interests of science(!), I know 100% that he would be horrified at the mere suggestion of it, and in all honesty I would be stressed every single day fearing that the cancer would return.  After all on diagnosis I was reassuringly told that my cancer was “beautifully hormone positive” with around 80% of cells exhibiting a strong positive response on testing, so it would take more than a few memory problems to make me step away from the holy grail that is Tamoxifen!

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