by Anna Browning
As the horror unfolds of the true devastation left by the Asian tsunami, the psychological impact on those left behind is harder to calculate.
It is feared the disaster could leave a mental "time bomb" if those caught up in it are not given counselling over the coming months.
Mental health charity Sane is calling for funds to provide such counselling.
Survivors need to be counselled within three months, says Sane
Without it, many could face flashbacks, nightmares and guilt at surviving, says its chief executive Marjorie Wallace.
That is not to say victims should be counselled straightaway. Evidence suggests that in the immediate aftermath of the disaster the instinct to survive kicks in - it is later that trauma can manifest itself.
"We are beginning to learn a great deal about how we cope psychologically after a natural disaster," said Ms Wallace.
"There was a time in the 1990s when it was felt that immediate counselling was the way forward after such events.
"The evidence now shows that using unselected counselling is not the answer, as that can interfere with the natural processes of resilience."
She said mass counselling, which was offered after Lockerbie, Hungerford and the Clapham rail disaster - which she herself had been involved in - had been proved ineffective.
Counselling was more useful within the first three months after the event, she added.
"The majority of people will be able to come to terms with it and ride out the most traumatic natural disaster.
"However, there is a significant minority who in the next few months will start experiencing the symptoms of post-traumatic disorder," she said.
This can include flashbacks and memories which survivors are unable to communicate.
People can also feel guilty of having survived and what might start as an "external" disaster can become internalised and leave the victim isolated.
Many experts in the field are thought to be finding that the peculiar nature of the tsunami disaster has brought other psychological problems too.
The giant waves hit in seconds without warning, taking over land and swallowing communities.
It has left many utterly insecure. Core beliefs that you are safe and so is your community have been totally undermined, as a result there are reports of a lot of stress seen in hospitals.
"It's very important that survivors receive information about what to expect, as well as advice - and quite practical advice," Ms Wallace continued.
"For some people they may need longer-term counselling and psychotherapy. But it is important to do something in the early months so as to prevent trauma going underground and being revived years later."
For the bereaved it is hardest to grieve without their loved-one's body
It is more worrying when victims internalise feelings and then become isolated from the communities they live in, she added.
It is not only survivors, but the bereaved too who will be hit, perhaps the hardest.
Many families may never find out what happened to their loved ones and may never recover the bodies.
Evidence shows "closure" helps families move on - something which may be denied to many left bereft by the tsunami.
Seeing their loved ones' for that last time is a vital step in the grief process for the bereaved.
Without it there can be an ambiguity - should they grieve or hope?
But above all else, voicing feelings of grief is vital, according to Ms Wallace.
"You can't take away the pain or the tragedy but you can help people in a lot of way in coming to terms with it," she said.
Simply watching events like the tsunami disaster played out in the media can also put psychological pressure on those who are mentally vulnerable or who have suffered previous trauma or bereavement.
Examples of this were the 11 September attacks by Islamic extremists, which aggravated flashbacks, serious distress, and other such symptoms in many watching events unfold at home.
"Our experience is that events on this scale can bring back memories of previous personal trauma and bereavement and that it helps some people to talk about their own 'trauma narrative'," said Ms Wallace.
"Certainly talking it through is very important. If you don't talk about it, it becomes distorted in your mind and that becomes very isolating," she said.
SaneLine, which gives information, advice and help for people experiencing mental anxiety or distress, is open throughout the year from 12pm to 2am on 0845 7678000