Dysthymia

A chronic depressive disorder, characterized by functional impairment and at least 2 years of depressive symptoms.

Reference:
Williams Jr, J. W., Barrett, J., Oxman, T., Frank, E., Katon, W., Sullivan, M., ... & Sengupta, A. (2000). Treatment of dysthymia and minor depression in primary care: a randomized controlled trial in older adults. Jama, 284(12), 1519-1526. doi: 10.1001/jama.284.12.1519