Continued stress and anxiety after traumatic experiences is far more common than realised, say experts.
PTSD is common and treatable, NICE says
Five in 100 men and 10 in 100 women will get post-traumatic stress disorder (PTSD) in their lifetime, the National Institute for Clinical Excellence says.
It says PTSD is under-recognised in the NHS and is urging better screening and treatment by issuing new guidelines.
Symptoms, including flashbacks, anger, anxiety and depression, can occur soon after a traumatic event or years later.
Up to 30% of people exposed to a stressful event of an exceptionally threatening or catastrophic nature, such as the September 11 terrorist attack or the recent Asian tsunami disaster, will go on to develop PTSD, research suggests.
But NICE says only a fraction of these cases are spotted and treated at present, particularly in children.
It says healthcare professionals should keep a watchful eye on individuals who have recently experienced a traumatic event to check for PTSD, arranging follow-up contact within one month of the event.
They should consider warning the loved ones of the individual about the risk of PTSD developing.
For example, they might alert the parents of youngsters who have been in road accidents to the possibility of PTSD, say the guidelines.
Watchful waiting may be all that is needed for some, but all those who go on to develop PTSD should be offered a course of psychological treatments, such as cognitive behavioural therapy.
Drug therapies should also be considered, but not first-line.
Giving people with PTSD a single-session to debrief them - going over the traumatic event - is not helpful, according to NICE.
Doctors should also look out for other conditions that can go hand in hand with PTSD, such as depression.
When the individual is a child, the therapy should be tailored to suit their age, the guidelines say.
The guideline developers admitted that implementing the recommendations would not be immediately possible in all NHS organisations due to a lack of resources.
Dr Jonathan Bisson, co-chair of the guideline development group and clinical senior lecturer in psychiatry at Cardiff University, said: "There are a lot of people who have not been diagnosed and treated.
"PTSD is a very real condition and it is treatable. It's a case of making those treatments available."
He said services were patchy across the UK and that resources needed to be redirected and more staff trained to treat PTSD.
Andrew Dillon, chief executive of NICE, said the guidelines offered "a starting point" for every NHS organisation across England and Wales.
Dr Monica Thompson, from the Trauma Stress Clinic, in London, said: "It is great to have these guidelines. They are really important in terms of accessing funding and service provision.
"It's really important to raise the understanding of PTSD among doctors and the public."
The Mental Health Foundation today welcomed the new NICE guidelines for post traumatic stress disorder as a significant step in the right direction.
Dr Andrew McCulloch of the Mental Health Foundation said: "We still have lots of work to do regarding PTSD, and need to learn how to better deal with it.
"We hope that the guidelines are rolled out effectively - it can be difficult to ensure that the patients feel the benefits with any speed. People in distress must get the help they need sooner rather than later."