Sex differences in trauma

 

 

 

Despite having spent much of my professional life dealing with post-traumatic reactions,  I rarely blog about it. One interpretation is that it arouses painful memories, but in fact most of my memories are positive ones of patients recovering, even if for some they were only partial recoveries. Mostly I speak about it less because others have very ably taken over the task of researching the topic and explaining the results to the public.

What interests me enough to come back to the issue is a paper about sex differences in trauma responses. Psychiatric illness is more common in women (mostly anxiety and depression) as most of the evidence shows. However, this paper makes a stronger claim about sex differences, and since I have been covering sex differences from the perspective of intellectual ability, this publication comes at an apposite time.

Lassemo, E., Sandanger, I., Nygård, J.F. et al.  The epidemiology of post-traumatic stress disorder in Norway: trauma characteristics and pre-existing psychiatric disorders

Soc Psychiatry Psychiatr Epidemiol (2016). doi:10.1007/s00127-016-1295-3

http://link.springer.com/article/10.1007/s00127-016-1295-3

In its favour, this paper comes from Norway, where they do proper epidemiology and keep track of people and their health and employment records. Against it, this paper comes from Norway, which lies on a warm bed of oil revenues, shields its citizens from major privations and always balances its budget. They also have an absurdly indented coastline and are prone to seasonal depression, skiing, and watching films about log fires. Are such people truly representative of the rest of humanity? Let us find out.

The methodology is good, the trauma measures fine, the assumptions on missing data reasonable, and the statistics almost easy enough for me to understand. I have some minor quibbles. The first two paragraphs of the results section are bewilderingly similar yet contradictory, as if they were setting us a “can you spot the difference” task.  Out of kindness to readers, the authors should re-write them. The frequent mention of one year and lifetime incidence and prevalence, probably corrected for age stratification confused me.

My other quibble is that they have somewhat under-displayed the sex differences, but I have tried to repair that by summarizing them for myself. First, here is their summary of their results:

The incidence for trauma was 466 and 641 per 100,000 PYs for women and men, respectively. The incidence of PTSD was 88 and 31 per 100,000 PYs. Twelve month and lifetime prevalence of PTSD was 1.7 and 4.3 %, respectively, for women, and 1.0 and 1.4 %, respectively, for men. Pre-existing psychiatric disorders were risk factors for PTSD, but only in women. Premeditated traumas were more harmful.

The authors have grouped all traumas into accidental and pre-meditated, a rough but useful distinction.

In the sample, more men (n = 203, 26.2 %) than women (n = 186, 21.7 %) were exposed to PTEs (potentially traumatic events)(p = 0.031). Of those exposed to trauma, more women (n = 38, 20.4 %) than men (n = 10, 4.9 %) filled diagnostic criteria for PTSD (p < 0.001), yielding a lifetime prevalence of 4.4 and 1.3 %, and a 12-month prevalence of 1.8 and 0.8 % for women and men, respectively. Given that PTEs are component causes for the PTSD diagnosis—necessary, but not sufficient, no individuals will have PTSD without having experienced a trauma. The sample had an underrepresentation of persons 18–34 years of age and an overrepresentation of persons 35–65 years of age, as compared with the Norwegian population.

I find the results section somewhat terse and hard to follow. So, I made some notes, as follows:

The sample of  1634 persons is composed of 859 women and 775 men.

Of the 859 women, 186 reported potentially traumatic events, of which 38 met the criteria for PTSD.

Of the 775, 203 men reported potentially traumatic events, of which 10 met the criteria for PTSD.

186/859 of women (21.7%) get a dose of bad events, and of those 38/186 (20.4%) get traumatized. Overall, facing the vicissitudes of life, 38/859 women (4.4 %) get traumatized.

203/775 of men (26.2%) get a dose of bad events, and of those 10/203 (5%) get traumatized. Overall, facing the vicissitudes of life, 10/775 men (1.3 %) get traumatized.

However, my summary is somewhat different from their tables, so by all means look through them, and try to make your own notes.  A little tree of frequencies would have been a help, particularly in understanding the all-important issue of dose-response relationships. (Perhaps this paper doesn’t get the Thompson prize for data analysis after all).

How much does previous psychiatric disorder contribute to trauma vulnerability?

The odds ratio (ORs) for conditional PTSD when suffering from pre-existing psychiatric disorders are presented, by gender, in Table 2. For women, any pre-existing depressive, anxiety or somatoform disorder was associated with an increased risk for PTSD [OR 3.6 (95 % CI 2.6–5.0)]. For women, pre-existing psychiatric disorder was associated with subsequent PTSD (p < 0.001). There were only a few men with pre-existing psychiatric disorders and traumatic exposure, and only one filled the diagnostic criteria for PTSD.

 

Notice the extraordinary impact on women of premeditated violence, mostly verbal threats, violence from relatives, sexual assault and rape.

In sum, slightly more men get exposed to bad events, but are much less likely to be traumatized by those events, particularly when they are older than 30. Even in tranquil and wealthy Norway, about a quarter of the population are exposed to troubling events. Of course we may wonder whether the self-reports are a function of the high standards all people in the wealthy world now expect from their lives. Would occupation by a foreign power increase the reporting rate, or re-set the scale as to what constitutes a potentially traumatic event? (I think the reporting rate would go up, but data on the bombardment of Beirut many years ago showed remarkable little change).

Even in Norway, the men are tougher, putting up with more slings and arrows of fate with less emotional injury. The supposed stereotype of tough men is validated, particularly those older than 30. The authors, however, note that the stressors are somewhat different, and have different incubation periods, with women ruminating in silence about past events. Of course, the selection of  what counts as upsetting is also sex-linked, so trauma will be a mixture of actual events and perceived injuries. Epictetus observed that: Men are disturbed not by things, but by the view which they take of them. To which I can only reply: To a certain extent, mate.

Women report more sexual abuse and rape, men more threats of physical violence.

There is lots more in the paper, so give it a look.

Finally, the authors make a point which has profound current interest: premeditation hurts people far more than true accidents. Some commentators tell us not to respond to0 much to terrorists because they don’t kill many people. Such commentators point out that rates of death from chronic disease are far higher, as are deaths from ordinary accidents and non-political criminal assaults. All this is statistically true yet misses the main point: it is the deliberate wish to kill people for who they are and how they choose to live which is rightly seen as an assault on freedom, and a source of dismay, incomprehension, and fear. Norway has experienced terrorism from the Right, but terrorism from any source raises a new category of existential threat, and requires us to cope with fresh pre-meditated hatred. Not nice, as my Granny used to say.