"Have had" versus "had"

Question

How does the usage of "have had" and "had" differ?

Here is my example from my other question:

People who have had their belongings taken will turn into miserable people.

Here are the things I seem to have gotten from StoneyB's answers:

• Have had is used for one-time occurrences, but had can be used for such occurrences as well
• Have or simple present is used for something more habitual

So does that mean have had and had are interchangeable?

People who have had their belongings taken will turn into miserable people. [= "People who had their belongings taken will turn into miserable people."]

Is this assumption correct, or do they imply different meanings?

So a sentence like "people who smoke will get sick" means that a habitual smoker will get sick, but a sentence like "people who have smoked will get sick" means that if you have smoked even once in your life, you'll get sick. Is this exact?

Answer 1

Essentially, the two sentences express the same thing: people who do not have their belongings anymore will turn into miserable people. For most people they will be interchangeable. There is a slight difference in the emphasis.

Using the present perfect emphasizes on the result. It talks about people who have had their things taken before now, at any point in the past; it doesn't matter when exactly, what matters is that they do not have them now. The result is important.

Using the past simple simply talks about an action at a moment in the past. In this case I would think we are talking about one particular occasion when someone took their belongings because I do not see anything in the sentence that implies repetition.

Whether to use "have had" or "had" depends on the context. If you are talking about a time when many things happened, one of which was that people had their belongings taken, then I would use the past simple because there is one particular past moment we have in mind. If there isn't one, and we want to say: "people who do not have their belongings now", then I would choose the present perfect.

About the second pair, you are right in your assumptions. Let me expand the phrases. The first one is: "people who normally/usually smoke". the second one is: "people who have ever smoked before/in the past (whether regularly or even once)".

Answer 2

This is old, but I have some thoughts regarding these sentences.

People who have had their belongings taken, turn into miserable people.

I would remove will because it seems redundant.

Or

People who have had their belongings taken become miserable people. People who have had their belongings taken often become miserable people. (I prefer the qualifier (often) to avoid over-generalization.

Saying it these ways has current relevance and suggests that people in the future will also become miserable. Thus, The present perfect.

If you said:

People who had their belongings taken often become miserable people.

This sounds a little bit odd because the past perfect describes an action that is complete in most cases and occurs before another past event which is not relevant in the future, often.

People who had their belongings taken in their past were miserable, according to an article published in 2017.

I don't know if you will see this given the age, and it is probably no longer relevant, but if it helps anyone, good!