It is important to relax before exams, a charity says
A mental health group is warning students not to worry too much about exams, amid fears over the effects of long-term stress.
The charity Mind found looming tests were causing problems including loss of sleep, binge drinking and headaches.
In some cases, stress led to acute depression and suicide.
Many students had nightmares about being under-prepared for exams long into adulthood.
A Mind spokesman said: "Exams are always a really difficult experience and everybody deals with them differently.
"Often, kids are not sleeping properly or are not going out and socialising as they would normally.
"It is important they don't deal with the stress all on their own.
"They should speak to their parents, peers or a relevant organisation. Perhaps students could organise revision groups or extra classes together."
Mind estimates the average pupil sits 87 exams during their school life.
It has published a booklet - How to Cope with Exam Stress - detailing self-help techniques, such as relaxation routines and controlled breathing.
Some students may benefit from talking to their GP.
Mind is also recommending revision techniques tailored to individual needs.
The spokeswoman said: "Students need to work out the best way of absorbing information for them.
"It may be that writing up notes from textbooks suits one person, but watching revision programmes may suit someone else better.
"Spending time on areas that are difficult and having regular breaks after around 45 to 60 minutes of revision can help to minimise stress.
"It is also important to get enough sleep, as a lack of it can make worrying worse."