The effects of cramming for an exam/for exams.
Cramming for an exam/for exams is to try to absorve a large quantity of information shortly before the exam/exams.
It can help you to pass. But, you can barely retain the information (you) reviewed after the exam. Also, if you are asked in the exam to use the information to help finding the correct answer, you probably won´t be able to.
*But, you can barely retain the information after the exam (I wouldn´t say that this way, to use "the" here, you have to specify which "information" you are talking about.
Also, if you were asked in the exam to use the information in order to achieve the correct answer,
you will probably not able to do it.
I, on purpose, separated the chunck into two parts, this way you can see clearly that there´s a mix of verb tenses. I suggested a redoing of it, my suggestion is the one above.