Gabriella, thanks for your complex case presentation.
PTSD is a condition that can developed as early as a month after experiencing or witnessing a stressful incident, as emphasized by Shalev et al. (2017). The individual exhibits symptoms such as sleep and concentration difficulties, engaging in self-harm, avoiding triggers related to trauma, experiencing irritability, losing interest in pleasurable activities, guilt for the traumatic event, dissociation, having distressing dreams or nightmares, engaging in reckless behavior, being unable to express positive emotions, and displaying thoughts or behaviors related to the trauma. In this patient’s case, he is showing several PTSD symptoms that, according to DSM 5 criteria, a provider can correctly diagnose the patient with. As a secondary differential diagnosis, I concur with you any significant event or trauma can lead to a diagnosis of GAD; again, this patient has experienced one of the most traumatic events, like witnessing the death of his father and subsequently moving to the United States, establishing relationships with new friends, possibly meeting new family members and attending a new school can all be contributing to the second differential. GAD is associated with multiple symptoms that the patient is displaying. Irritability, lack of concentration, and sleeping disturbances. (James et al., 2020).
References
James, A. C., Reardon, T., Soler, A., James, G., & Creswell, C. (2020). Cognitive behavioral therapy for anxiety disorders in children and adolescents. Cochrane database of systematic reviews, (11). https://doi.org/10.1002/14651858.CD013162.pub2
Shalev, A., Liberzon, I., & Marmar, C. (2017). Post-traumatic stress disorder. New England
Journal of Medicine, 376(25), 2459-2469.