His health has not been improved by all the upset at home.

Not all medical treatments work. Not all medical treatments will work for a particular condition. All medical treatments in fact may not help certain kinds of conditions. If you have a medical treatment which doesn't work for your condition, while medical treatment in general is a good thing, in your case it doesn't help, so in that particular case it isn't a particularly good thing. The upset at home did not help his condition, and quite probably made it worse, the implication being that quiet and calm instead of upset would have helped, or at least not made things worse.

Thank you~

But in that sentence isn't there the implication that the editor of the dictionary thinks usually UPSET can help people improve their health?

No. The implication is that upset does not improve health (which is what the sentence in fact says).

When we say "His health has not been improved by being hit on the head", we are not implying that being hit on the head is a good thing or effective at improving health. We are in fact saying the opposite. The dictionary is right.

There is no implication that the editor of the dictionary, or anyone else, thinks that upsets can improve health. You have to take 'not improved' as a phrase in its entirety. We use this type of expression when a desired outcome is prevented or postponed by something.

John's appearance was not improved by the large food stain on his jacket.

There can be a jocular nuance: that is to say, a kind of joke is being made to emphasise the point.

My chances of promotion at work will not be improved if I punch the boss.

The flavour of curry is not improved by the addition of coal dust.

The safety of the process was not improved by the storage of gasoline near to a furnace.

The speech was not made more intelligible by the frequent coughing of the speaker.

The atmosphere in the hotel room was not made more fragrant by the presence of a three days dead dog outside the open window.

I understood it!

Thank you~

The example sentences are excellent.

I must make a distinction clear:

When I say that my chances of promotion at work will not be improved if I punch my boss, I am making a humorous understatement. This type of expression is common, certainly among British speakers, and maybe elsewhere. The statement is true, of course, but in fact my chances of promotion will be reduced to zero because I will be immediately dismissed, and will probably be arrested by the police and charged with (at least) assault. This happened to someone I once knew. He knocked his manager unconscious, and he got three months in prison.

Likewise a curry will actually be rendered inedible by the addition of coal dust.

However, in your originally quoted sentence, "His health has not been improved by all the upset at home.", we cannot assume that the subject's health has been destroyed, only that no improvement has taken place. His health might have deteriorated, or it might have remained at a constant level, instead of improving as is (presumably) desired.

Thank you~ The answer is very good!