Epidemiological trends in mental disorders are shown against a background governed by medical aid health policy. The study quantitatively analyzed a dataset of mental disorders for South Africa’s leading medical aid scheme. South Africa’s leading medical aid scheme has been in operation for almost three decades. This degree of longevity allows for a reliable longitudinal analysis of diagnostic trends. Through consent of the Scheme, a database was provided, which lists mental disorder diagnoses over seven years from 2008 to mid-way through 2015. Data from this source were analyzed and interpreted. Data fields provided and made use of from the raw medical scheme database are: Date of admission (Year, Month); Patient gender; Database population per year; Patient diagnosis (DEG Description); Total per DEG Description. Each diagnosis (mental disorder) is presented in the following ways: 1. Bar charts showing the volume of specific mental illnesses each year. 2. Bar charts showing fluctuations of occurrence of a specific mental illness over time. 3. Frequency of specific mental illnesses over time, relative to the entire database population. 4. Male:Female ratio per mental disorder. 5. Female Outpatient vs. Inpatient volumes across each mental disorder and across all years (2008 – 2015).v 6. Male Outpatient vs. Inpatient volumes across each mental disorder and across all years (2008 – 2015). 7. Total number of patients per mental disorder across time (2008 – 2015). 8. Frequency polygons showing the fluctuation of a selected mental disorder over time as compared to other selected mental disorders. It is found that there are changes in prevalence rates of mental disorders over time and that these fluctuations are attributed to an economic factor within medical aid scheme cost-driven policy. The effect of cost-driven policy is that members diagnosed with a mental disorder may not be granted provision of adequate treatment because diagnosis is in part, determined by economic structures. Costs for mental illness treatment programmes are curtailed by keeping patient numbers significantly low, by radically over-diagnosing certain mental illnesses treated with comparably cheaper pharmaceuticals or by drastically curbing time spent in a mental health facility. Some members of the medical aid scheme have been deliberately misdiagnosed. Alternatively, those, correctly diagnosed, do not receive the treatment required of such an illness. The scenario then is of thousands of mentally ill people, who are not treated effectively. Members continue to pay fees, paying under the illusion that medical cover ensures effective treatment / Psychology / M.A. Psychology