Rumination
It is generally thought that those who ruminate, especially those who brood, have a higher likelihood of getting depressed and falling into a deeper depression than those who do not. This association seems to hold even when you account for people being depressed at the start of the study, and to be valid across ages and populations. Ruminating is also suggested to make people more vulnerable to other risk factors for depression such as gender, less memory of one’s own life, neuroticism, negative thinking styles and perfectionism. The effects of the other kind of rumination, reflection, are more varied. Even though it is generally agreed that the this style of rumination is related to less depression overall, and especially a smaller likelihood of developing depression in the future, new research points to the connection between the reflection and self-critical ruminative thinking (often thinking the same mean thoughts about yourself).