TSH alone is not enough. YOu have been treated for hypothyroid for many years. TSH may not be the best test to tell us what is going on with you.
We need to see FT3 and FT4 results. If your doctor hasn't yet tested these, this is the next step.
Let us know.
Please provide a little more background information.
What thyroid meds are you on, and what's the dose?
In addition to TSH, is your doctor testing free T3 and free T4? If so, please post results along with reference ranges. Ranges vary from lab to lab and have to come from your own lab report.
Do you have Hashi's?
What other symptoms do you have besides depression?
To answer your question directly - yes, imbalance in thyroid hormones can be a major contributor to depression.