Psychotraumatisms are very frequent in the context of liaison psychiatry. The history of the concept of trauma highlights important evolution debates between clinicians, and the long time that has been needed to recognize the veracity of a traumatic event on the health. Although, trauma is historically associated to war, several medical conditions such as cancers, HIV infections, acute coronary syndrome, strokes, intensive care unit hospitalization are associated with a high rate of post-traumatic stress disorder (PTSD). These medical traumatic events have also consequences on healthcare workers that can also develop PTSD. Regarding the numerous psychiatric and physical comorbidities and the social impact of PTSD, prevention and strategies must be developed in the context of liaison psychiatry and must take account of the specificity of trauma following a medical event. In the context of liaison psychiatry, the management of somatoform symptoms constitute a big challenge. Data show that these symptoms result from previous traumas underling dissociative mechanisms. Inflammatory mechanisms appear as a key mechanism to explain physical symptoms following trauma exposure such as chronic pain, cardiometabolic disease, neurocognitive disorders, and dementia.

This thesis comprises four original publications. The first study leading on traumatic childbirth and birth-related PTSD following childbirth and the second and the fourth study leading on patients hospitalized for COVID-19 pneumonia show all the three the interest of systematic screening of risk factors to prevent PTSD. The third study highlights peritraumatic reactions and PTSD related to their work in healthcare workers during the first wave of COVID-19 pandemics. Further studies are needed to develop prevention and treatment strategies for the psychotraumatic components in the liaison psychiatry field, including systematic screening of risk factors of PTSD, early treatment such as single EMDR session following a trauma, emerging treatments such as neurofeedback or augmentation of Imagery Rehearsal Therapy with targeted Memory Reactivation. Further studies are also necessary to better understand pathophysiology somatoform dissociative disorders and somatic symptoms resulting from trauma exposure. Some data suggest inflammatory mechanisms and disrupted functional connectivity in brain are involved and that could open new strategies treatments.