Antidepressant treatment in primary care is inconsistent with treatment recommendations, and many patients discontinue treatment within 6 months. How this affects treatment outcomes is unknown. The aim of this study was to assess how length of theirst antidepressant episode influences risk and time to a second treatment episode within 5 years.The study population included 9423 adults (67% women; mean age, 47.3 years) who initiated selective serotonin reuptake inhibitor use in 1998 or 1999. Basedon the length of the first antidepressant treatment episode, patients were divided into early discontinuers (<6 months), continuing users (6-12 months), and persistent users (>12 months). The Cox proportional hazards model was used to estimate risk ratios (RRs) for the association between the length of the first antidepressant treatment episode and time to reinitiating antidepressant treatment.Time to a second treatment episode did not differ significantly between continuing users and early discontinuers (RR, 0.99; 95% confidence interval, 0.92-1.07). Persistent users showed a higher risk of experiencing a second treatment episode than early discontinuers (RR, 1.23; 95% confidence interval, 1.15-1.32).In conclusion, the risk of experiencing a second antidepressant treatment episode did not differ for those who used antidepressants for 6 to 12 months and those who discontinued early. In general, there is limited information on how length of an antidepressant treatment episode influences the risk of reinitiating treatment of patients in primary care. More research is needed to investigate the effectiveness of antidepressant drug treatment patterns in preventing relapse or recurrence in primary care populations.