Psychiatrists know from extensive research on New York's population, as well as across the US, after 9/11, combined with experience from other traumas, that some will be so psychologically scarred they will never be able to commute again. These are most likely to be those who escaped but were trapped on the Underground, or on that bus, or the road in close proximity to the explosions. How proximal you come to a close shave with death predicts how likely you are to suffer from severe psychological difficulties, such as post-traumatic stress disorder (PTSD).
The symptoms include hyper-vigilance - every time sufferers hear a siren, or the Tube shudders to a halt, their mind automatically catapults to the worst possible inference as to their personal safety, rendering a normal life impossible. Insomnia, nightmares and flashbacks are a cluster of symptoms of PTSD.
But you didn't have to be on the bus in Tavistock Square or on the Underground at Edgware Road, Russell Square or Aldgate to be profoundly psychologically affected. Modern instant communications technology combined with a hyper-vivid media beaming intense eyewitness experience and testimony, means there is now a sense we have all journeyed on those buses and trains with the casualties and survivors. These were people doing very ordinary things and in the very neighbourhoods we can closely identify with.
Psychiatric research into 9/11 confirms that those who watched the rolling news media most incessantly, even if they were thousands of miles away from New York, were often as likely to be as traumatised as those who were actually there.
But a series of studies has found that the closer you live geographically to the location of a disaster, the higher your chances of developing PTSD. Another discovered almost half of the total US population experienced at least one symptom of PTSD in the week after 9/11.
Those most affected emotionally are going to be the more socially isolated - and loneliness is a worryingly common problem in a large, anonymous city like London. Perhaps the most widespread sentiment, though, is a kind of listlessness as previous preoccupations now seem so trivial in comparison to the enormity of what has happened.
But there is a particular psychological issue. It is the deep problem for survivors and relatives of never knowing what actually happened to the victims. These kinds of events are almost psychologically unique in the long-term torture they can inflict, by depriving knowledge of the last moments of loved ones, leaving an empty dark space where only nightmares can roam.
Dr Raj Persaud is Gresham professor for public understanding of psychiatry and consultant psychiatrist at the Maudsley Hospital in south LondonReuse content