Females in Combat
I saw dead people
The second study, by Wessely's team, which looked at nearly 6000 British soldiers who had served in Iraq in 2003, reached similar conclusions (Psychological Medicine, DOI: 10.1017/S0033291708004595). The researchers found no indication that the symptoms ascribed to PCS were caused by an mTBI. While many of those who reported such symptoms had indeed been caught in a blast, some had not. In fact, blast exposure proved no more predictive of PCS symptoms than other stressful combat situations, such as seeing dead bodies or knowingly being exposed to depleted uranium. The findings suggest that the symptoms "are most often an expression of psychological distress", says Wessely.
Michael Jaffee, however, who is national director of the DVBIC, warns against assuming that the symptoms ascribed to PCS are caused exclusively by either an mTBI or by PTSD. Since any kind of combat injury raises the risk of PTSD, and since you are more likely to show PTSD symptoms after a head injury, "there is bound to be overlap", he says.
Jaffee wonders if there might be something about blast-induced brain injury that makes people more vulnerable to psychological disorders, and to PTSD in particular. PTSD is characterised by impaired function in parts of the prefrontal cortex that help regulate how we deal with fear and anxiety and mTBI often involves damage to the prefrontal cortex. Jaffee and others suggest that this sort of damage may disrupt a person's capacity to deal with fear and thus make them more susceptible to PTSD (Journal of Rehabilitation Research and Development, vol 44, p 895).
Wessely questions this kind of association because "when you get concussion you lose your memory, so how can you have flashbacks when you don't remember the incident?". But concussion does not always involve amnesia. Furthermore, Hoge says, traumatic memories can trigger PTSD even when you are not conscious of them.
In any case, does it matter to the patient what the cause of their symptoms is? Many researchers say it matters a great deal. Plenty of studies have shown that what you tell a patient about what is wrong with them has a big influence on how long they take to get better. "If they believe they are going to have lifelong impairment as a result of a brain injury, they are more likely to have persistent symptoms," says Hoge. "On the other hand, individuals who have positive expectations, who are told they are going to get better, actually do better."
Wessely and Hoge even avoid the term mTBI when talking to patients. "The phrase 'traumatic brain injury' makes it sound like you have shrapnel in your skull and will end up in a wheelchair," says Wessely. "Call it concussion and they'll think, I had that playing rugby."
Another reason why understanding the true cause of PCS matters relates to whether it should be screened for. The US military screening programs have found that up to 18 per cent of its returning personnel have had an mTBI. Figures from the UK military, on the other hand, which does not carry out mass screening, suggest that fewer than 1 per cent of its troops have suffered an mTBI.
Why such a big difference? It is possible, of course, that US troops get blown up more, or perhaps have weaker protective helmets. But another explanation is that US doctors find more head injuries simply because they have systematic screening in place, while British soldiers have to decide they have a problem and take the action of going to see their doctor.
So might the US be over diagnosing the problem, or the UK under diagnosing it? Lionel Jarvis, the UK's assistant chief of the UK defence staff (health), thinks the former. Jarvis points out that any soldier returning from a six-month tour of duty in Afghanistan, where they've been away from their family and in an extreme, high-pressure environment, is likely to show symptoms of distress: "How on earth do you unpick the different symptoms and explain whether they are due to a head injury or one of a large number of other potential causes?"
Wessely says his study showed that screening soldiers for PCS when they get home cannot distinguish between those whose problems were caused by concussion and those who have anxiety, depression or PTSD. "It's fraught with danger," he says. "Caution is needed before labeling mTBI as an epidemic because this might become self-fulfilling."