Most people recover after disasters by drawing on their own strengths and the support of others. Recovery rates are high: generally less than one in ten of those affected by disasters develop chronic, long-term problems.
However, being a sole survivor of a mass casualty may have its own complex psychological challenges.
Survivor's guilt
Survivors can experience guilt they lived when others died.
My friend, Gill Hicks, spoke to me for this article about the ongoing guilt she still feels, years after surviving the 2005 bombings of the London underground.
Lying trapped in a smoke-filled train carriage, she was the last living person to be rescued after the attack. Gill lost both her legs.
Yet she still wonders, "Why me? Why did I get to go home, when so many others didn't?"
In the case of a sole survivor, this guilt may be particularly acute. However, research addressing the impact of sole survivorship is limited. Most research that looks at the psychological impact of disaster focuses on the impact of disasters more broadly.
Those interviewed for a 2013 documentary about surviving large plane crashes, Sole Survivor, express complex feelings - wanting to share their stories, but fearing being judged by others.
Being the lone survivor can be a heavy burden.
"I didn't think I was worthy of the gift of being alive," George Lamson Jr. told the documentary, after surviving a 1985 plane crash in Nevada that killed all others on board.
Looking for meaning
People who survive a disaster may also be under pressure to explain what happened and relive the trauma for the benefit of others.
Vishwashkumar Ramesh was filmed and interviewed by media in the minutes and hours following the Air India crash. But as he told his brother: "I have no idea how I exited the plane".
It can be common for survivors themselves to be plagued by unanswerable questions. Did they live for a reason? Why did they live, when so many others died?
These kinds of unanswerable questions reflect our natural inclination to look for meaning in experiences, and to have our life stories make sense.
For some people, sharing a traumatic experience with others who've been through it or something similar can be a beneficial part of the recovery process, helping to process emotions and regain some agency and control.
However, this may not always be possible for sole survivors, potentially compounding feelings of guilt and isolation.
Coping with survivor's guilt
Survivor's guilt can be an expression of grief and loss.
Studies indicate guilt is notably widespread among individuals who have experienced traumatic events, and it is associated with heightened psychopathological symptoms (such as severe anxiety, insomnia or flashbacks) and thoughts of suicide.
Taking time to process the traumatic event can help survivors cope, and seeking support from friends, family and community or faith leaders can help an individual work through difficult feelings.
My friend Gill says the anxiety rises as the anniversary of the disaster approaches each year. Trauma reminders such as anniversaries are different to unexpected trauma triggers, but can still cause distress.
Media attention around collectively experienced dates can also amplify trauma-related distress, contributing to a cycle of media consumption and increased worry about future events.
On the 7th of July each year, Gill holds a private remembrance ritual. This allows her to express her grief and sense of loss, and to honour those who did not survive. These types of rituals can be a valuable tool in processing feelings of grief and guilt, offering a sense of control and meaning and facilitating the expression and acceptance of loss.
But lingering guilt and anxiety - especially when it interferes with day-to-day life - should not be ignored. Ongoing survivor guilt is associated with significantly higher levels of post-traumatic symptoms.
Survivors may need support from psychologists or mental health professionals in the short and long term.