Do SSRI antidepressants reduce the effectiveness of Tamoxifen? Is there an alternative to an SSRI?

I finished chemotherapy on October 28 and have started on Tamoxifen and Zoladex. I am not bothered too much by the menopausal symptoms except I am experiencing depression and anxiety. I had severe depression about 10 years ago which was effectively treated with councelling, Zoloft and Effexor. I have not taken antidepressants for 6+ years and until now have not relapsed. My doctor wants me to start on an SSRI but I have read this will reduce the effectiveness of the Tamoxifen. Should I be concerned? Is there an alternative to an SSRI (such as an older antidepressant) which will not interfere with Tamoxifen, Zoladex or Zometa? (St John's Wort, it works in the same way and had no thereputic benefit for me). Is the depression just a result of adjusting to menopause and will it go away by itself? It is quite debilitating and I am annoyed that it has struck me now, just as I am feeling physically better and my life was starting to get back to normal. Diet, councelling and exercise are not helping me. If this continues then I will need to start antidepressant medication, I am worried I will suffer depression to the same extent as when I was younger.