For writing an essay on this problem you might want to focus on specific group of patients that are at particular risk for depression. Three groups which the New York State Department of Health has identified as having a high risk of depression and suicide are AIDS patients, cancer patients, and the elderly.
As the first two groups both are patients managing serious illnesses, an upstream intervention would include offering affordable mental health services at the time of diagnosis. In the United States, even with the Affordable Care Act, patients will spend thousands of dollars or more out of pocket when they become ill, meaning that a condition such as cancer or AIDS is a financial as well as a health crisis. Rather than mental health care being yet another expense which patients might forgo for financial reasons, making mental health care for these groups freely available and offered at the time of diagnosis and treatment, would be an upstream intervention, before the problem becomes acute.
For the elderly, social isolation is a contributing factor to depression. One of the major issues for making mental health programs accessible to the elderly is logistical. With the exception of New York City, many parts of New York state are highly car dependent, meaning that the elderly who can no longer drive not only become socially isolated but lack convenient and affordable transportation to mental health care. An upstream intervention might be creating a program in which psychology students at local universities visit the elderly and do two things, first administering surveys which might diagnose early signs of depression and second simply offering an hour or so a week of social interaction. It would benefit the students by giving them hands-on experience and the people visited by giving them the company of young people.
Upstream interventions are policy approaches that can include regulation or incentivization. These are high level interventions that have the ability to affect a large number of persons. Upstream interventions can be aimed at preventing a problem before it occurs, or mitigating the effects of a problem which has already occurred.
In the case of depression in adults, an upstream intervention would be focused on improving access to mental health care. This might include providing free or low-cost services, providing transportation to these services, screening campaigns and/or marketing aimed at decreasing the stigma associated with seeking mental health care. An example is the New York State Psychiatric Institute's Depression Evaluation Service, which provides no cost evaluation and medication treatment in collaboration with Columbia University.