On 14 July 2016 in Nice, celebration day in France, a terrorist attack happened. Many children and their families were impacted physically and psychologically. At least 30,000 people were present on the Promenade des Anglais (the attack site). This is the most important terrorist attack against families and children in France.

Eighty-six people died in the attack, including 10 children, the youngest being 4 years old. At least 55 children and adolescents were bereaved because of this crime. From 14^th 2016 to the beginning of the “14–7” Program (November 21^st, 2017), 827 outpatients children, aged less than 18 years old, have consulted the child and adolescent psychiatry service as results of clinical consequences of this attack (1).

After being exposed to a traumatic event, children and adolescents may suffer from several clinical conditions (2). Among them, the most common is post-traumatic stress disorder (PTSD) (2). PTSD includes four main clinical symptoms: flashbacks of the event, avoidance behaviors, alteration of cognition and mood, and neurovegetative overactivation (3). Moreover, children and adolescents have specific clinical symptoms, such as general fears, developmental regression or traumatic re-enactment through play (4).

PTSD contributes to the development of many other mental disorders (5, 6). Around 75% of children and adolescents with PTSD have comorbid disorders. The main comorbidities identified in the pediatric populations are anxiety disorders, attention-deficit-hyperactivity disorder and depression (7, 8, 9). In addition, children and adolescents might present reactive attachment disorder, sleep disturbances and behavior problems (such as oppositional defiant disorder) (8).

Rates of PTSD in children and adolescents exposed to a potentially traumatic event have been shown to vary between 6% and 20% depending on several factors (10). That is, trauma history and exposure, sociodemographic, psychiatric, psychologic, environmental, and biological factors may modulate the development of PTSD.

Concerning trauma history and exposition, it has been reported that individuals who experience multiple trauma are at higher risk of developing chronic PTSD (11). In addition, the degree of violence, the individual experiences during the exposition, is known to influence the development of PTSD (12). However, whether the exposure is direct or indirect does not seem to have an impact on PTSD development, but it may have an effect on its chronicity (13). Repeated trauma cause more PTSD in children and adolescents than single events [35% (14) vs. 18% (15)]. The prevalence of PTSD after a human attack (more than 50% (16, 17) might be much higher than after other traumas [23% to 30%, after a natural disaster (18, 19), 17% after road accidents (15, 20)]. A higher prevalence of PTSD after a mass attack compared to other types of trauma is also described in adults [39% vs 10% (21, 22)].

Among sociodemographic factors, age, sex, socio-economic status (15) and psychosocial resources (23) have been associated with different varying risks of PTSD. Some studies assumed that being a woman or a girl has been found associated with higher risk of PTSD development after a traumatic event (24). Younger children might have a higher prevalence of PTSD compared to older ones [39% for under 6 years versus 33% for 6–11 or 27% 12 years and older (9)]. People with lower socioeconomic status (15) and with depleted psychosocial resources (23) seem at greater risk of PTSD development. Consistent effects were found for these variables in PTSD severity (9.2% more) and PTSD onset (8.75% more), while the results are less obvious concerning racial/ethnic differences in PTSD persistence (5.40% more).

Among psychiatric factors, having anterior mental disorders, and in particular depression, anxious disorders, or PTSD (25) is associated with higher intensity of acute stress reaction and higher risk of peri-traumatic dissociation (26). Moreover, the risk of PTSD chronicization is increased when the child develops PTSD comorbidities (27).

Concerning psychological factors that have been found related to PTSD, the feeling of fear, during trauma and in the first month after the exposition to the traumatic event, is a risk factor implicated in the PTSD development (28). In a similar way, guilt and shame after the event predict the development of this disorder (29). Finally, cognitive alterations, that is, alterations of working memory and executive functioning and attentional biases are correlated with the occurrence and the risk of transition to PTSD chronic state symptoms (30).

Among environmental factors, family reactions during and after the trauma modulate the risk of PTSD development (31). Parental distress as well as parental PTSD and other parental mental disorders conduct to a higher risk of PTSD in children and adolescents (32, 33). On the contrary, quality of familial and social support, available psychological health care, recognition of traumatic impact by the society (31) have been identified as protective factors of PTSD development.

Finally, researches on adults have shown three biological markers of PTSD development: low cortisol 24 h after trauma (34), reduction of the volume of the hippocampus (35) and prefrontal dysfunction (36). Studies underlined that individuals with decreased hippocampus volume and prefrontal dysfunction following exposure displayed more PTSD-related symptoms 1 month after. In contrast, initial smaller hippocampus volume pre-exposure did not have an effect on PTSD-related symptoms (35).

Although several risk factors of PTSD in both children and adults have been documented, most research on risk factors of PTSD development in children and adolescents has focused on a small number of factors. Therefore, there is to date no integrative model of the PTSD development, and of risk of chronicity or relapse. Research on adult PTSD attempts to demonstrate the existence of different PTSD patterns consistent with symptoms, trauma and comorbidity (37) and to understand the temporal courses of PTSD (38). These results have not yet been replicated in children and adolescents.

Because both children and parents were exposed to the event and because of the nature of traumatic event, the prevalence of PTSD in the pediatric population implicated in the Nice attack may be very important.

The primary objective of the “14–7” Program is to characterize the risk and/or protective psychosocial factors affecting the clinical evolution of a pediatric population sample exposed to the terrorist attack of July 14^th, 2016 in Nice.

Secondary objectives of the “14–7” Program are to examine efficacy of clinical treatments as a function of the developmental age of the child, and to develop recommendations for treatments and therapies.

Two groups were defined:

Patient selection and recruitment:

Exposed children are recruited by consultation registry of the Nice CHU Lenval, ORSAN database (a national list of victims from terrorist attack). Controls will be matched on age and sex. Moreover, participants will be recruited via press advertisements and National Education. For the control group, categorical screening criteria were used to estimate the number of subjects necessary to reach a statistical power of 80% with a risk of type-I error (α) of 5% for the main outcome variable. Assuming a frequency of development of PTSD of 20% in the general population, to demonstrate a 40% increase in incidence (incidence rate found during violent and intentional traumatic events), it is necessary to include 1,122 participants; that is, 561 child controls. We will then include 600 children (150 per centre) matched on age and sex to the group of exposed children.

It has been reported that psychiatric disorders such as PTSD have a high prevalence in war-exposed children (61), and more generally in intentional trauma (62). However, research on psychotrauma in terrorism context on pediatric population is rare and/or very fragmented, and there are few reliable data in children and adolescents exposed to traumatic events (63).

Most epidemiological studies have involved either small samples of number of participants or very heterogeneous samples. For example, in some studies, participants have experienced different types of trauma and in other studies, a very small number of factors related to PTSD have been investigated [for a meta-analysis, see Ref. (31)]. In others, very few factors related to PTSD have been investigated such as quality of life [Ref. (31); see also Ref. (18)]. Then, one of the main advantages of the “14–7” Program is that it includes multiple assessments (psychiatric, psychological, psychosocial, biological, and cognitive), on a population of children having experienced the same traumatogenic event. The interest of “14–7” Program is to understand better clinical and cognitive specificities of trauma in pediatric population. Moreover, “14–7” Program integrates a developmental and biological approach.

Children and adolescents are also vulnerable for conduct, attention, and others psychiatric disorders after a PTSD development (8). An acute understanding of the clinical, cognitive, social, and biological consequences of trauma are necessary to orient specific follow up and treatments of the impacted pediatric population.

The main strength of the “14–7” Program is the standardized evaluation and follow-up of a large number of children and adolescents impacted by a terrorist attack in a country in peace, with assessments until the young adult age (25 years).

The American Academy of Child and Adolescent Psychiatry (AACAP) recommends early interventions for children and adolescents to reduce clinical manifestations of trauma (64). AACAP also suggests that relying on the support of the young patient’s family, school, and friends is important, and that psychotherapies should allow the child to talk about the traumatic event in a safe space by speaking, drawing, playing, or writing. Unfortunately, no recommendation on the types of therapies to use and on their duration has been provided so far (64).

The studies involving human participants were reviewed and approved by National Ethics Committee “NORD OUEST III.” Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

MG wrote the manuscript. ST, AS, FG, and MB are the proofreaders. FA is the writer and the coordinator.

This work has been supported by the Université Côte d’Azur.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.