Cognitive behavioral approaches have been able to demonstrate some of the underlying and perpetuating factors of depression such as cognitive reactivity (CR). The association of CR and the severity of depression is yet to be reported. We aimed to compare the CR of a group of outpatients based on their self-reported severity of depression (SRSD), and to identify the role of specific CR vulnerability markers in depression. The study population consisted of 221 outpatients diagnosed with Major Depressive Disorder. We used the Mini International Neuropsychiatric Interview, and completed a demographic and clinical data form. The participants completed the Leiden Index of Depression Sensitivity-Revised (LEIDS-R), and the Hospital Anxiety and Depression Scale. To identify how well CR, as measured by the scores of the LEIDS-R, could discriminate the groups based on the SRSD, one-way analysis of variance was used. To examine the unique associations between the CR and the SRSD, a hierarchical linear regression analysis was performed. To identify group membership to severe depression, the scores of the LEIDS-R were entered in a logistic regression model. Large, and small group differences emerged on the rumination, and control scores, respectively. The other group differences were all in the medium range. The control, risk aversion, and rumination scores were the subscales which explained a significant proportion of the variance in the SRSD. Overall, the logistic regression model classified 93.7 % of the severely depressed patients correctly. These results indicated that rumination, risk aversion, and perfectionism were particularly associated with severe depression.