Having given it a bit more thought: there's more. Everyone has one thing or a few things that sort of soothe them. If you can get that or have it done, it helps. When I am soothed, I am less anxious, and that lessens the weight of the depression. It will be different things for different people. For me it is: my bed having been made in a certain way, a long soak in the tub (this one only works a handful of times), cotton clothing (if possible, freshly washed and ironed), dim lights, and open windows. Eating breakfast late at night also helps me.
If you could find what those things are for your son, you could do them for him. You don't have to do everything at once or do something each day, but on particularly difficult days or perhaps at random, you can do some of those things.
Please ensure you are also receiving some care as the caregiver, because you are very important, and needed, and valued.