Introduction

Post‐traumatic stress disorder (PTSD) is a common response to trauma in children and adolescents (Alisic et al., 2014) that is prognostic of longer‐term deleterious impacts on mental health and functioning (Bolton et al., 2004; Morgan, Scourfield, Williams, Jasper, & Lewis, 2003). PTSD is a near‐unique disorder in that its onset can be linked to a particular event. However, mental health professionals and diagnostic systems typically steer away from diagnosing PTSD in the first month after a trauma as it is recognised that some degree of acute traumatic stress symptoms represents a normative response. Prospective studies of trauma‐exposed youth support this view, with considerable natural recovery occurring in the weeks and months following trauma (Hiller et al., 2016). The diagnosis of acute stress disorder (ASD) has been proposed by the American Psychiatric Association (APA) (2013) to identify individuals with high levels of clinically significant symptoms in these first 4 weeks post‐trauma, who are deemed at elevated risk of later PTSD.

Two important questions are then apparent: Why do only some young people have significant traumatic stress symptoms in the days and weeks immediately post‐trauma while others do not, and why do some youth then recover without treatment while others go on to suffer from persistent PTSD? Cognitive theorists propose that individual differences in the way the trauma is psychologically processed shape these differential responses and trajectories (Brewin, Dalgleish, & Joseph, 1996; Dalgleish, 2004; Ehlers & Clark, 2000). Central to these models is the contribution of peritraumatic cognitive processes that operate at the time of the trauma to the initial acute onset of traumatic stress symptoms. These processes include subjective experiences of threat and panic, ‘data‐driven processing’ (i.e. overwhelming sensory impressions and confusion during the trauma, where the individual has difficulty in making sense of the trauma as it occurs) and dissociation. Several additional post‐traumatic cognitive processes are then proposed to maintain post‐traumatic stress symptoms (PTSS) over time. These include the presence of a poorly elaborated, fragmented and sensory‐based memory of the trauma (as a function of the aforementioned peritraumatic processes), cognitive and behavioural avoidance of trauma‐related stimuli, negative appraisals of the self and world following the trauma (e.g. believing that one cannot cope, that one's reactions are a sign of permanent psychological damage or weakness), rumination (e.g. persistent thinking around difficult to resolve questions such as ‘why did this happen to me’, ‘what could I have done differently’) and persistent dissociation, which is proposed to impede the elaboration of trauma memories (Ehlers & Clark, 2000).

While some efforts have been made to consider the contribution of cognitive processes in youth, these studies have focused largely on the role of negative trauma‐related appraisals (Mitchell, Brennan, Curran, Hanna, & Dyer, 2017). While other cognitive mechanisms such as data‐driven processing (McKinnon, Nixon, & Brewer, 2008), trauma memory quality (Salmond et al., 2011) and rumination (Stallard & Smith, 2007) have also been shown to be associated with post‐traumatic stress, the studies were small and cross‐sectional in nature, and/or have used single‐item measures of the constructs of interest (Ehlers, Mayou, & Bryant, 2003; Stallard & Smith, 2007). The few studies that have utilised a prospective design have typically done so beyond the acute window (i.e. in the first days and weeks following a trauma) when most natural recovery would be anticipated to occur (Palosaari, Punamaki, Diab, & Qouta, 2013). The full range of cognitive processes proposed by cognitive models of PTSD has not been examined together within the same study in youth. Moreover, these cognitive processes have not been considered in the context of other plausible pre‐, peri‐ and post‐trauma predictors of onset and maintenance of traumatic stress symptoms, to clarify their independent role in driving psychiatric outcomes.

The current prospective longitudinal study of children and adolescents aged 8–17 years recently exposed to a traumatic stressor allowed for a comprehensive examination of this important issue. The study addressed symptoms of PTSD 2–4 weeks and 2 months following a trauma, when much natural recovery is still occurring. In particular, we sought to consider three questions. First, we examined whether cognitive processes would account for unique variance in PTSS over and above the effect of demographic factors, trauma nature and severity variables, and psychosocial factors not specifically implicated in cognitive models of PTSD (i.e. social support, life stressors). Second, we sought to investigate whether, consistent with cognitive models of PTSD, distinct cognitive mechanisms have a specific role in either the onset (e.g. peritraumatic factors such as subjective threat, panic and data‐driven processing) or maintenance (e.g. appraisals, rumination) of PTSS. To this end, we compared three groups: a ‘resilient’ group who did not develop clinically significant traumatic stress symptoms at either time point; a ‘recovery’ group who initially had clinically significant symptoms but not clinically significant symptoms at follow‐up; and a ‘persistent group’ who had clinically significant symptoms at both time points. Third, we also examined whether active attempts to process the trauma, for example talking the trauma through with friends or family, measured at the 2‐ to 4‐week assessment may be protective against PTSS at 2 months.