In order to write this op-ed piece, you are going to need to do two main things. First, you are going to need to argue that there is a significant need for doctors specializing in the treatment of depression in adults. Second, you are going to need to argue that the forgiveness of student debt would be a good way to attract doctors to this particular field. You have to make both of these arguments to have a good case for debt forgiveness.
There is no real case for debt forgiveness unless there is a need for doctors in this field. In order to prove that there is such a need, you would need to provide numbers showing how many adults suffer from depression and how many doctors there are who specialize in treating them. You would like to show that the number of doctors is insufficient to handle the number of patients needing treatment. Ideally, you would be able to compare the current doctor to patient ratio in this field to the ratio in some other field. If you could show, for example, that the ratio in cardiology is much higher (more doctors per patient), then you would have a better argument that there are not enough doctors specializing in adult depression.
However, proving that there are not enough doctors is only the first step. You also need to be able to show that debt forgiveness would be a good way to remedy the problem. If debt forgiveness does not pull more doctors into this field, then it would just be a waste of money. In order to prove that debt forgiveness is a good policy, you would ideally show that it has worked in other situations. For example, has debt forgiveness been used to attract doctors to underserved places in the country? Has it been used to induce doctors into any other specialties? If so, that would constitute proof that debt forgiveness can actually work in the way you want it to.
If there is no such evidence, you should at least prove that doctors’ debt loads are onerous. You should give some sort of statistic about how much debt the average doctor has when he or she finishes medical school. You could then compare that to the average salary that a beginning doctor might expect to earn. If you can show that the average doctor has an excessively high amount of debt (when compared to expected income), it would help the reader to believe that debt forgiveness would be a real incentive for a doctor to go into a given field.
In order to write a convincing op-ed on this subject, you will need to convince us that there is a need for doctors to work with adults with depression and that debt forgiveness is a good way to increase the number of doctors willing to engage in this kind of work.