"Dysthymic" refers to a condition where a person experiences a persistent low mood or mild depression for a long period of time, typically lasting for two years or more.
Sertraline and / or interpersonal psychotherapy for patients with dysthymic disorder in primary care: 6 - month comparison with longitudinal 2 - year follow - up of effectiveness and costs. (cebc4cw.org)
Browne, G., et al., Sertraline and interpersonal psychotherapy, alone and combined, in the treatment of patients with dysthymic disorder in primary care: a 2 year comparison of effectiveness and cost. (iptinstitute.com)
Sensitivity was much lower for diagnoses of major depression within the previous year, lifetime diagnosis of dysthymic disorder, and all anxiety disorders within the previous year (table ⇓). (ebmh.bmj.com)