This study determined whether naturally-occurring, but significantly different, outpatient follow-up frequencies are associated with clinical outcome and service waiting time. It 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. 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.