Background: Depression is the leading cause of disease burden globally and most of the people with this illness left untreated. Remission without treatment may occur in some cases of depression. The aim of this study was to estimate the spontaneous remission (natural recovery) of people from this untreated depression.

Methods: Systematic review, conducted in accordance with PRISMA guidelines and registered on PROSPERO, CRD42020198773. We have used two-steps approach searching EMBASE, PsycINFO, and PubMed supplemented with additional relevant sources to identify studies reporting natural recovery from untreated depression. First, we systematically searched for existing reviews and then we conducted a search for original studies. Study selection and screening were carried out by three independent reviewers. Methodological quality assessment of the included studies was conducted. The data were synthesized using narrative summary and random-effects meta-analysis.

Results: From 2,574 identified unique records, 16 studies were included in the systematic review and meta-analysis fulfilling the eligibility criteria. Most of the included studies were randomized waitlist control trials. The overall pooled remission from untreated depression (natural recovery) was 22.6% within widely varied follow-up duration ranged from one month to six years. The remission was 11.4% within three months of follow-up period and 49.2% within six months or more duration.

Conclusions: Remission within a short untreated period is not common where 1 in 10 people may be remitted within 3 months duration of untreated depression. Interpretation of the result should be considered with caution as the data from waitlist controls may represent mild or moderate depression.