I am grading student assignments and I ran into some unforeseen complications:
Children have been suffering from post-traumatic stress and depression, more than six months after the city had been heavily flooded.
a) Is the use of the present perfect progressive acceptable. b) How about the past perfect after "after"?
Teenagers have begun to suffer from depression after they had seen their grades drop.
Is the past perfect acceptable?
It depends.
Are the children suffering now? Then I would suggest using the present tense and putting the second clause in the past simple.
Children are still suffering from from post-traumatic stress and depression, more than six months after the city was flooded heavily.
If the children are no longer suffering from depression then use the past simple tense and the past perfect in the second clause.
Children were suffering from from post-traumatic stress and depression, more than six months after the city had been flooded heavily
A third option is possible using the perfect aspect. The present perfect continuous is used for an action which began in the past and has not finished, but still continues in the present.
Children have been suffering from from post-traumatic stress and depression, for more than six months after the city flooded.
You didn't say whether your students are native speakers of English, nor whether you are.
It makes a difference.
A native speaker of English would, by saying the sentences aloud, realize that, while not all of these constructions are equally frequent in native speech, they are all perfectly ordinary and grammatical, with past, or perfect, of all varieties
... provided that ...
the events reported in the past perfect happened before everything else.
A non-native speaker of English, however, may have been taught that there is a strict rule called Sequence Of Tenses that governs every clause in every sentence, with terrible (but unstated)
penalties for violation. This is of course not true, but many wish it were, and try to enforce it.
For that matter, most native English speakers are taught this kind of mythology in school, too,
but luckily it's usually ignored, except by the credulous.
