The Mirena releases a hormone which, according to its website, is quite common in birth control pills. I know those
can cause mood issues, so it's no surprise to me that the Mirena can do the same.
As for the spotting, the website says that's normal still:
|Q. How will Mirena affect my period?
A. At first, you may experience spotting (a small amount of blood loss) or light bleeding requiring sanitary protection in addition to your monthly period.
* This usually occurs during the first 3 to 6 months after Mirena is placed
* During this time, your period may become irregular
* A few women may have heavy or prolonged bleeding during this time
After this brief adjustment period, your number of bleeding days is likely to decrease, and your periods may even stop altogether. By 1 year of use, there may be up to a 90% reduction in menstrual bleeding and about 20% of users have no bleeding or spotting at all.
And here we go, mood changes are a recognized side effect:
|Q. What about side effects?
A. In clinical studies, the most common side effects with Mirena included:
* Menstrual changes
* Lower abdominal pain (cramps)
* Acne or other skin problems
* Back pain
* Breast tenderness
* Mood changes
Ovarian cysts have been diagnosed in about 12% of Mirena users.
In most cases, these cysts disappeared spontaneously during 2 to 3 months' observation. Women who have, or have had, breast cancer should not use hormonal therapy.
In theory, the mood changes should decrease over time; while 2.5% have that side effect at 3 months, less than 1% do at the five-year mark.
Here is the Mirena website; my quotes came from the FAQ section:http://www.mirena-us.com/index.html?C=&c=
ETA: Being that this contraceptive contains a common active ingredient from birth control pills, I'd suggest you expect the same issues you had if you have taken the Pill in the past.