I read somewhere that Tramadol works a bit like an SNRI, so it's definitely possible it improves your mood.
I was on tramadol for 9 months or so - on a kickass dose of 600 mg (which is a lot anyway, but especially if you consider I was 14 years old at the time). It didn't make the pain even close to bearable (I could have 200 mg tramadol, 2400 mg ibuprofen, 1000 mg acetaminophen in my bloodstream and still spend hours screaming - it was BAD. The decision to have my leg amputated was the best decision ever. Post-surgery pain and phantom pain were/are negligible in comparison), but without it was even more unbearable.