At one time, there was concern that women who used hormonal contraception (including Depo, the pill, the ring, etc.) were experiencing more cases of cervical dysplasia. However, the association between hormonal contraception and cervical dysplasia is thought to be due to the absence of using other forms of birth control (condoms), rather than the hormones "causing" cervical dysplasia.
In other words...women who were use hormonal birth control were not using condoms, and one primary cause of cervical dyslplasia is sexually transmitted diseases (STDs), specifically HPV, that can (mostly) be prevented by use of condoms (hormonal birth control can not protect against STDs).
There are other causes of cervical dysplasia...some are genetic, and many are unknown. Here is a very helpful online brochure that talks about the different types of cervical dysplasia: American College of Obstetrics and Gynecology (ACOG): Understanding Abnormal Pap Test Results and ACOG: Cancer of the Cervix. (Please know: the cancer of the cervix brochure talks about benign and abnormal cells, not just cancerous cells. It is still helpful in your situation).
The recommendation for follow-up treatment is anywhere from a repeat Pap smear every 3, 6, or 12 months; I've most often seen between 6-12 months. Your doctor would know best, depending on the specific type and severity of your dysplasia.
I am wondering, however...why did you receive the Depo shot only twice in 5 years (when it is supposed to be every 3 months?). Were you using any type of other birth control methods, such as hormonal (ie, pill) or barrier (ie, condom).
Thanks for your question...please let us know if you have any further questions.