Job strain seems to be a strong predictor of burnout and of depressive symptoms but not of depressive disorder. The apparent contradiction could just be a measure of the low conversion rate from burnout to depression or, that job strain is not a predictor of depression.
Previous history of mental disorder is a very strong predictor of burnout, depressive symptoms and current depression.
K Ahola et al. JOEM (2006) Vol.48#10 p 1023 – 1030.
“Contribution of Burnout to the Association between Job Strain and Depression: the Health 2000 Study”
High job strain was predictive of burnout OR = 7.4 (95% CI = 5.6 to 9.6). High job strain was also predictive of depressive symptoms (OR of the order of 3.9) but was inconsistently related to depressive disorders in all the analyses and especially when corrected for burnout.