Early childhood adversity such as physical and sexual abuse, emotional neglect, parental loss, etc., are major risk factors for the development of a range of psychiatric disorders in adulthood, including posttraumatic stress disorder (PTSD) 
. PTSD occurs following exposure to a traumatic event and is defined by distinct symptom clusters of re-experiencing, avoidance and numbing, and arousal persisting for more than 1 month after trauma 
. PTSD can have severe long-term consequences and individuals who develop PTSD have an increased risk of major depression, substance dependence, and other health conditions, as well as impaired role functioning and reduced life course opportunities 
Recently, links between trauma, PTSD and increased risk of dementia have been suggested. According to several pieces of evidence from animal and human studies, stress experienced early in life induces structural, functional, and epigenetic changes in brain regions involved in cognition, predominantly in the frontal and temporal lobes and the hippocampus 
. Animal studies demonstrated that early life stress-induced increase of glucorticoids significantly influenced the degree of cognitive impairment with age 
, which is in accordance with the glucocorticoid-cascade-hypothesis of aging 
. The latter postulates that chronic stress can lead to an increase of cortisol-release which can cause hippocampal atrophy (central region for learning and memory processing). Similarly, several previous study findings have shown that mood disorders such as depression may be associated with a distinct pattern of cognitive impairment 
In humans, research has shown that around 70% of individuals suffering from dementia report at least one severe traumatic event before the onset of the disease, as reported by a study conducted at an Dementia Outpatient Clinic in Greece (n
. In the like way, in a seminal retrospective cohort study including n
181′093 predominantly male US war veterans, those who had suffered a PTSD (n
53,155) had a two-fold increased risk of developing dementia compared with their counterparts without PTSD (n
. In addition, PTSD did not appear to be associated with a particular dementia type but rather had an ‘across-the-board effect’ for all dementias, including vascular dementia and Alzheimer's disease. These findings were supported in another recent group comparison study conducted by Qureshi and colleagues, using n
10′481 US war veterans recruited through the Veterans Integrated Service Network 16 
. Veterans aged 65 and older with a diagnosis of PTSD or who were recipients of a Purple Heart (PH) and a comparison group of the same age with no PTSD diagnosis or PH, were divided into four groups and prevalence of dementia was compared across these groups. Results indicated higher incidence and prevalence of dementia in veterans with PTSD compared to veterans without PTSD 
. Although these findings have important implications for preventive care, it remains to be investigated whether this association is due to a common risk factor underlying PTSD and dementia or to PTSD being a risk factor for dementia.
Overall, current literature suggests that PTSD is associated with cognitive impairment, and a greater incidence and prevalence of dementia. However, whether PTSD-related cognitive changes represent an early marker of dementia or whether they act as risk factors for later dementia needs to be further investigated. Whilst clear associations between adult trauma and cognitive impairment have been repeatedly found, only few studies have measured the long-term consequences of childhood trauma on cognitive function and PTSD in elder individuals. Although such an effect is very likely given that modifiable or stable biographical, psychological, genetic, individual and social factors are causal for the development of dementia, literature reporting on this topic is fairly inconsistent 
. For example, in a recent study, Majer and colleagues investigated a group of healthy adults with significant exposure to early-life trauma and concluded that physical neglect and emotional abuse might be associated with long-term and working memory deficits in adulthood 
. Since the authors did not include individuals suffering from PTSD or other trauma-related psychiatric disorders, their study does neither allow to draw conclusions on the association between these disorders and cognitive dysfunction nor does it provide information on the influence of the time-point of traumatization ( i.e. adulthood, childhood) on the extent of cognitive symptoms. Moreover, their restricted sample size (n
47) might have introduced a bias; therefore replication in bigger samples is needed. Two other studies investigating intelligence, memory and learning deficits in groups of trauma-exposed and non-exposed children and adolescents found no association between cognitive performance and traumatic events in early life 
. Saigh et al. compared the IQ scores of traumatized youth with PTSD to scores of trauma-exposed and non-exposed comparison groups without PTSD whilst controlling for other major childhood psychiatric disorders. The PTSD group consisting of n
228 individuals scored significantly lower on the verbal, but not on the performance subtests compared to the n
276 controls 
. Furthermore, the scores of the trauma-exposed non-PTSD individuals and non-trauma exposed controls were not significantly different indicating that PTSD and not a history of trauma exposure (without PTSD) is associated with lower verbal IQ. Similarly, Yasik and colleagues found youth with PTSD (n
29) to have significantly lower scores in verbal memory indices compared with non-traumatized control subjects (n
40) but no significant differences for general memory or visual memory
. The studies expand on the literature documenting memory impairments among adults with PTSD. However, additional research is needed to explore the relation between trauma exposure, diagnostic status, and cognitive performance across a broader range of neuropsychological indices.
To further investigate the role of PTSD as a potential mediator or moderator variable in the association between trauma and cognitive impairment and to determine the influence of PTSD resilience, it is therefore crucial to not only compare cognitive function in individuals with and without prior traumatic experience, but also to look at individuals who developed a PTSD and those who did not. Given also the limited information and inconsistency of current literature, more research is needed to explore the links between cognitive performance and traumatic events early in life. It is likewise possible that the effects of childhood trauma on cognitive function differ in strength from traumas experienced in adulthood and therefore need to be analyzed separately.
The aim of this study was to investigate the association between childhood trauma exposure, PTSD symptoms and cognitive function in a sample of elder adults. To the best of our knowledge no other studies have investigated and compared levels of cognitive function of cohorts of individuals having been exposed to childhood trauma to cohorts of individuals with adulthood trauma. According to previous studies we hypothesized that exposure to childhood trauma, as well as PTSD symptoms would be significantly associated with poorer cognitive function, especially in memory-related domains. To test these hypotheses, childhood trauma exposure, PTSD status, and neurocognitive function was assessed in a unique sample of former Swiss indentured child laborers.