Online self-help is an innovative way of providing self-help. The investigators want to study the effect of an interactive online self-help-program (Deprexis) in the treatment of severe depressive symptoms. Participants will be randomised to either twelve weeks of online-self help or a waiting-list control. Symptoms of depression and other aspects will be assessed over a six months period. The investigators hypothesise that online self-help is superior to the control condition in alleviating depressive symptoms and preventing full blown depression.

Inclusion Criteria:

• Age between 18 and 65, ability to read German, willingness to participate in a telephone diagnostic interview, achieving a score of at least 15 on the PHQ-9 in an initial screening, and providing written informed consent

Exclusion Criteria:

• Lifetime diagnosis of schizophrenia or bipolar disorder (as determined by a telephone diagnostic interview) or current suicidality (as determined in a telephone interview)