Background: Cross-sectional studies show that the prevalence of comorbid depression in people with tuberculosis (TB) is high. The hypothesis that TB may lead to depression has not been well studied. Our objectives were to determine the incidence and predictors of probable depression in a prospective cohort of people with TB in primary care settings in Ethiopia.

Methods: We assessed 648 people with newly diagnosed TB for probable depression using Patient Health Questionnaire, nine-item (PHQ-9) at the time of starting their anti-TB medication. We defined PHQ-9 scores ten and above as probable depression. Participants without baseline probable depression were assessed at two and six months to measure incidence of depression. Incidence rates per 1000-person months were calculated. Predictors of incident depression were identified using Poisson regression.

Results: Two hundred and ninety-nine (46.1%) of the participants did not have probable depression at baseline. The incidence rate of depression between baseline and two months was 73.6 (95%CI= 42.8, 104.3) and between baseline and six months was 24.2 (95%CI= 14.9, 33.5) per 1000 person-months respectively. Female sex (adjusted ẞ= 0.22; 95%CI= 0.16, 0.27) was a risk factor and perceived social support (adjusted ẞ= -0.14; 95%CI= -0.24, -0.03) was a protective factor for depression onset.

Conclusion: There was high incidence of probable depression in people undergoing treatment for newly diagnosed TB. The persistence and incidence of depression beyond six months needs to be studied. TB treatment guidelines should have mental health component.

Key terms: depression, tuberculosis, incidence, primary care, Ethiopia