Why some are more susceptible to developing PTSD symptoms than others

‘It is very difficult to investigate why some people show symptoms after a trauma and other people do not,’ explains De Voogd (now working at Leiden University). ’For a good measurement, you have to be there before people experience something bad, but you don't know in advance whether someone is going to experience something traumatic.’ That is why the researchers, together with the National Police, set up a large-scale study called ‘Police In Action’. They examined police officers at the beginning of their training, before they took to the streets: they are more likely than average to experience something traumatic in the years that follow.

Gun or phone

The police officers in training had to carry out a shooting task in an MRI scanner. They were shown an avatar in a car park that initially did nothing. De Voogd: ‘At a certain point, the avatar pulls out a gun or a mobile phone. The participants had to react quickly by either shooting the avatar, or not. If the participant made the wrong decision and shot while the avatar was pulling out a phone, they received an electric shock on their finger. ‘All kinds of things happen in the brain when a participant sees the avatar but does not have to do anything yet. The participant is already preparing to take action later on.’

After about 18 months, the police officers in training were asked what they had experienced and whether they experienced any PTSD symptoms. ‘We saw that people who had a more active amygdala before a trauma when performing the shooting task experienced more PTSD symptoms after a trauma.’

Making people more resilient

We do not know exactly why the amygdala reacts more strongly to threat in some people than in others. ‘It's possible that some people take in more information under threat than others and are therefore more attentive in crisis situations, but we need to investigate this further.' The advantage of knowing what makes someone more susceptible to trauma is that you can make that person more resilient earlier on. De Voogd: ‘If you can make the amygdala more calm, you may also be able to reduce the chance of PTSD symptoms.’