According to the Centers for Disease Control (CDC) peer-reviewed article "Measuring the Impact of Public Health Policy" (Brownson RC, Seiler R, Eyler AA. Measuring the impact of public health policy. Preventing Chronic Disease 2010;7(4):A77), interventions are made in three levels, which are also called "streams", as proposed by Kingdon's policy making model. They are called "streams" because the goal is "to move policies forward" the way that streams move forward their currents. It all breaks down like this:
Stream 1: Define the problem
Stream 2: Implement and develop policies to fix the problem
Stream 3: Public and social support
Stream 3 would be the "upstream" intervention. This consists on a series of approaches that come from the top down, in the form of rules and regulations at-large, which are meant to affect large groups of people.
In the case of depression, we know that it is a medical psychological and biological condition that can worsen during the senior years. This is because this is a time in the human lifespan when the body starts to lose its former strength of youth. As a result, normal processes start to slow down or end altogether, such as bone strength, circulation, organ and systemic activities. The brain is also affected in different ways, sometimes with conditions that come with age such as Alzheimer's, and some with environmental input such as isolation, stagnation, grief, loss, mourning, and poor elderly care.
As with this latter factor, an upstream intervention would be making laws at the federal and state levels that will mandate at least 1 hour of free, daily counseling to elderly patients who wish to get it. It should also be an upstream intervention to ensure that the process of getting this care is not difficult nor complicated, and that a system is in place to let the elderly participant have easy access to the intervention. This could be in the form of free transportation, or for a clinician to provide the service at home. There are programs already in place with a similar concept which are part of comprehensive health benefit packages. An upstream intervention will ensure that everyone is equally benefitted whether they are part of the package or not.