Dr. Patricia Yarberry Allen is a collaborative physician who writes a weekly Medical Monday” column for Women’s Voices for Change.  (Search our archives for her posts, calling on the expertise of medical specialists, on topics from angiography to vulvar melanoma.)

This week, Dr. Pat has asked Megan Riddle, M.D./Ph.D., a psychiatry resident at the University of Washington and a graduate of the Weill Cornell/Rockefeller/Sloan-Kettering Tri-Institutional MD-PhD Program, to address the concerns of a woman who is taking tamoxifen and wonders how that affects her disturbing menopausal mood swings.


Dear Dr. Pat:

I had breast cancer two years ago. It was found early, and I had a lumpectomy and radiation postoperatively. I am taking tamoxifen, since the cancer was strongly estrogen-positive.  My last period was one year ago, and I am now 50.  

I can manage the hot flashes, since they aren’t so frequent, and frankly aren’t nearly as bad as I had thought they would be. However, I have real mood issues that I can’t afford, since I need my job and would like to stay married.  I used to have symptoms like these before my period—really nasty mood swings for 24 hours.  Now I cry, lose my temper often, and am unpredictably agitated and anxious. I am no longer sleeping for more than four hours, and when I wake up I have a lot of trouble getting back to sleep because I start to worry and think about all the things that are going wrong in my life. Actually, I don’t have a bad life, so this is troubling as well. I used to be an optimistic person, so this new person I have become is hard for me to live with.



Dr. Riddle Responds:

Dear Sarah:

thI am glad to hear that your cancer was found early and that you are now in remission, but am sorry to hear that you are struggling with your mood. Cancer can take a significant toll on your emotional health, for a number of reasons. Up to one in four individuals with cancer develops depression, which can seriously impact quality of life even as the cancer goes into remission.

Furthermore, sometimes the treatments themselves can influence your moods. For tumors like yours that are responsive to estrogen, drugs that block estrogen activity in breast tissue can play a critical role in treatment. While some studies report that these drugs do not tend to influence mood, you certainly would not be the first woman to find that they can lead to mood swings and increased irritability.

The good news is that we have treatment options. Many women find that antidepressants are useful in dealing with these symptoms. It is important, however, that the doctor who prescribes your antidepressant is aware you are taking tamoxifen. For tamoxifen to work, your liver must break it down to its active form, using a specific enzyme called CYP2D6. Some popular antidepressants such as paroxetine (Paxil), fluoxetine (Prozac), and bupropion (Wellbutrin), suppress the activity of this enzyme. This means that these medications will make the tamoxifen less effective, and so they should be avoided. Studies have borne this out, showing increased risk of death from breast cancer in individuals who take tamoxifen and Paxil.

Instead, the antidepressants venlafaxine (Effexor) and desvenlafaxine (Pristiq) have been shown to have little effect on the CYP2D6 enzyme and are thus good choices for those taking tamoxifen. In addition to improving mood, these medications have been shown to be helpful in reducing hot flashes, thus providing additional benefit in treating the side effects of tamoxifen.

Your oncologist may be able to recommend a psychiatrist experienced in treating individuals with cancer. Many cancer treatment centers have psychiatrists on staff specifically to work on addressing the mental health component of cancer care. Please reach out to your current provider.



Desmarais, J. E., & Looper, K. J. (2010). Managing menopausal symptoms and depression in tamoxifen users: implications of drug and medicinal interactions. http://www.ncbi.nlm.nih.gov/pubmed/20880642 Maturitas, 67(4), 296-308.





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  • Megan Riddle January 28, 2015 at 8:10 pm

    Dear Kathleen,

    Thank you so much for sharing your story. I am so glad to hear you are doing well and thank you bring up some very excellent points. A huge component of our mental wellness is how we spend our time. Often modifications like you mention – making changes to get enough sleep, being sure to exercise, engaging in self-care activities – can have a significant impact on our mood. Congratulations on 16 cancer free years!


    Megan Riddle, MD PhD

  • Kathleen O'Keefe-Kanavos January 26, 2015 at 3:32 pm

    Sarah, I’m so happy your cancer was found early.I am a three time breast cancer survivor (16 and 11 years ago now), who learned an important lesson concerning Tamoxifen- it appears to be working due to mood swings, etc, but can stop working for many women after two years. Unfortunately, follow-up blood tests seldom check for an increase in hormone levels, an alert to doctors that the drug no longer works. The patient must ask for a hormone check. Fortunately, there are alternatives to Tamoxifen. Mine was Arimidex aka (anastrozole). Sarah, when we are diagnosed with a life-threatening disease it changes our life, especially our sleep patterns. Worry can become constant. However, know that more women than ever before are living a normal life after diagnosis. Tears are an emotional release that wash the soul. But, if they interfere with your life then I agree with Dr. Riddle’s response to seek professional help. Here are 3 holistic ways I dealt with sleep issues during and after my treatment: 1.) Don’t eat after 6pm so your digestive system will not be active and give you undue energy, 2.) I had a soft work-out program before bed that included dancing to music in the bathroom. It made me fit, happily exhausted and I slept like a baby. 3.) Journal your experiences so you can actually read and track your improvements. This will give you Peace-of-Mind that will carry through into your daily life. After my second cancer was found to be hormone responsive while still taking Tamoxifen I switched to Arimidex. That was 16 years ago. Hang in there, Sarah. There is a happy and fulfilled life after cancer. And you have an army of sister & brother survivors in your corner with you cheering you on. Big Hug.
    Kathleen O’Keefe-Kanavos