Van Loo 2018.

Study characteristics
Study details	Sponsorship source: Not reported Country: USA Setting: Community setting Year of recruitment: 1988 ‐ 1997 Author's contact details: Department of Psychiatry, University of Groningen, University Medical Center Groningen, Hanzeplein 1, PO box 30.001, 9700 RB Groningen, The Netherlands. h.van.loo@umcg.nl (H.M. van Loo)
Methods	Type of study: Model development study Source of data: Longitudinal cohort study* Method used for model development: Cox proportional hazards model with elastic net penalised regression analysis Method used for internal validation: Random split "test" sample. The final model was selected based on minimal prediction error as assessed in 10‐fold cross‐validation External validation: Not done Handling of missing data: Multiple imputation by chained equations Evaluation of clinical utility: Not reported
Sample size	Total number of participants (Number with event): Total sample (men and women): 653** Number of candidate predictor parameters: 70 predictors (number of parameters unclear) Number of predictors in final model: 24 Number of events per candidate predictor parameter (EPP): Unclear
Population	Inclusion criteria: Episode of MD in year prior to baseline interview Exclusion criteria: No MD episode in year prior to baseline interview Those who reported an interval of 60 days or less between the offset of their last MD episode at baseline and their first depressive episode during the follow‐up
Baseline characteristics	Mean age (SD): 35 (8.8) Gender (% female): 34.6
Start‐point (diagnosis of depression and remission)	Depression: A diagnosis of MD in the year prior to baseline interview was based on the DSM‐III‐R criteria as assessed by the Structured Clinical Interview for DSM‐III‐R Remission: All participants reported a period of > 60 days of (partial) remission or recovery
End‐point (diagnosis of relapse/recurrence)	Recurrence: First reported episode meeting DSM‐III‐R criteria in the year prior to follow‐up interview Time to recurrence: Time at risk for recurrence (follow‐up) was defined as the interval between the offset of MD in the year prior to baseline interview and the onset of MD in the year prior to follow‐up interview
Timing (length of follow‐up)	5 years
Notes	*Virginia Adult Twin Study of Psychiatric and Substance Use Disorders (VATSPSUD), a population‐based longitudinal study of male–male and male–female Caucasian twin pairs **This was the full sample size, including men and women. There were also separate analyses in women (n = 226) and in men (n = 427). The male cohort was split further into a training sample (n = 277) and a test sample (for external validation)