Objectives: This study determined whether naturally-occurring, but significantly different, outpatient follow-up frequencies are associated with clinical outcomes and service waiting times. Study Design: Longitudinal retrospective study. Methods: This study was conducted in an outpatient setting. Participants consisted of 340 patients with major depressive disorder who were randomly assigned to four psychiatrists and were followed at a variable frequency defined by the clinician. Patients were assessed at baseline and at every visit with structured interviews and self-reported questionnaires. These groups were also compared according to their baseline characteristics, treatment and appointment frequencies. Little’s law was used to estimate the impact of modifying the appointment frequencies on the service waiting time. Results: The demographic variables, prescriptions and depression severity at intake of patients across the four groups were similar. The mean times between appointments of the four groups were significantly different (87.0, 46.9, 67.9, and 61.5 days, respectively; p<.001), but these differences in outpatient follow-up frequency were not associated with clinical outcomes (e.g., last Quick Inventory of Depressive Scale (QIDS-SR) score (10.5, 10.0, 11.9, and 9.7; p=.25)). However, different outpatient follow-up frequencies had an estimated impact on waiting times for access to care; using Little’s Law, it was observed that the waiting list would be eliminated by reducing by 23.9% the follow-up frequencies of the three psychiatrists with the highest frequencies. Conclusions: While variations in appointment frequencies do not appear to have a major impact on clinical outcomes, they could be managed to achieve significant improvements in the accessibility of the clinic.