One of the more entertaining aspects of major depression is that it does not immunize you from getting depressed. Why? Because they are not the same animal. It is quite likely that he has been depressed and got over it. We all have but that has little to do with major depression.

I will not describe the criteria for diagnosing major depression. Many have done it much better than I could. You might want to do some googling if you have not done so already. Identify what is best for you which may be sticking or moving on.

No judgement here. With love, good luck.