Having one's child being diagnosed with a severe chronic disease or hurt through an unintentional injury is one of the most severe stressors that parents can experience. Parents' often react with posttraumatic stress symptoms (PTSS) or posttraumatic stress disorder (PTSD) [1–7]. PTSS following a traumatic event include persistent frightening thoughts and memories of the ordeal (re-experiencing), avoidance of thinking about the event and feelings of numbness, and increased arousal. PTSD is diagnosed when these symptoms last for more than a month and cause significant functional impairment. In the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) , learning that one's child has a life-threatening illness qualifies as a traumatic event. Traumatic events can be a single dramatic event (Type I trauma) or repeated traumatic events (Type II trauma) .
While fathers were neglected for a long time in research investigating families of pediatric patients, a few more recent studies report on fathers' posttraumatic stress reactions. Elevated levels of PTSS during and after treatment were found in fathers of pediatric cancer survivors [1, 2, 6, 10–12]. In fathers of children with type I diabetes, a significant group met the criteria for full or partial PTSD [13, 15]. In a study comparing PTSS and PTSD in fathers of children with different acute and chronic conditions, the highest rates of PTSD were found in fathers of children with newly diagnosed cancer, whereas rates in fathers of children with diabetes and physical injuries were similar . However, in that study the occurrence of PTSS and PTSD was investigated with a cross-sectional design at a relatively early time point in the treatment course (4–6 weeks after diagnosis or injury). Prospective studies of PTSD in fathers examined either fathers of pediatric cancer survivors or fathers of children with newly diagnosed type I diabetes separately [2, 15], but no previous study has compared the course of PTSS in fathers of children with different chronic and acute conditions.
Depending on the research focus, interest in factors that predict fathers' adaptation to their child's disease has been selective. Several theoretical models [16–19] have been developed to describe and illustrate predictors of and processes associated with the adaptation of parents to the stress of their child's disease. Most of these models are derived from the stress and coping model  and share as a conceptual basis the view that the child's disease is a potential stressor. Cognitive appraisal and coping constitute the central adaptation processes. These processes are influenced by different predictors that can be categorized in illness-related factors (diagnosis, treatment intensity, and others), individual differences (such as socio-demographic variables, personality characteristics), and familial factors (such as social support, family relations).
Regarding illness-related factors, one study reported that the child's functional status and the length of hospitalization were significantly correlated with PTSS levels in fathers of patients with different acute and chronic conditions . In contrast, no or only minimal associations between objective medical parameters (such as intensity of treatment, length of time since diagnosis) and levels of PTSS were found in fathers of pediatric cancer patients or survivors [7, 10, 11]. Rather, fathers' perceptions of cancer threat (that is, whether the child could still die) and cancer treatment contributed significantly to their PTSS levels.
Few findings exist regarding the role of personality as a predictor of fathers' psychological adjustment. Findings from studies employing the "Big Five" framework of personality domains, which is the gold standard for personality measurement to date, have shown that extraversion, conscientiousness, and agreeableness predict better adjustment to stress, whereas neuroticism predicts poor adjustment [21, 22]. However, the Big Five personality domains have never been examined in fathers of pediatric patients. Studies in parents of pediatric cancer survivors that investigated trait anxiety, a measure closely related to neuroticism , found that it functioned as a risk factor for the development of PTSS. Whereas one study demonstrated that trait anxiety was a significant predictor of PTSS for both fathers and mothers , another found trait anxiety to be a predictor of PTSS in mothers but not in fathers . Among additional psychological predictors investigated, poorer family functioning  and satisfaction  and lower levels of perceived social support [11, 24] were found to be associated with higher levels of PTSS.
To our knowledge no results are available on associations between personality factors other than trait anxiety, subjective appraisal of distress, or coping and PTSS levels in fathers of children with chronic diseases or unintentional injuries. Some limited findings exist regarding psychological symptoms that are associated with coping in fathers of children with different chronic diseases, indicating that fathers relying on strategies such as avoidance coping , behavioral disengagement, or venting of emotions  report more symptoms.
The first aim of the present study was to compare prevalence and course of PTSD and PTSS between fathers of children with unintentional injuries and fathers of children with a chronic disease during the first six months after the injury or the diagnosis. With respect to prevalence and course of PTSD and PTSS of fathers of unintentionally injured children or fathers of children with a chronic disease we expected the initial levels of posttraumatic stress reactions to be similar in both groups. Over the course of time, however, we expected to find differences between the groups. We hypothesized to see elevated PTSS levels over the first months of the treatment in fathers of children with a chronic disease but declining PTSS levels in fathers of children with unintentional injuries. The second aim of the present study was to examine the role of illness-related factors, personality, family relations, stress appraisal, and coping in predicting fathers' levels of PTSS. We hypothesized, that higher levels in neuroticism, lower levels in extraversion, agreeableness, and conscientiousness, as well as poorer family relations, and the use of dysfunctional coping strategies shortly after the diagnosis or the injury, would predict elevated PTSS levels several months later.