Years after he barely survived a terrorist attack that killed his wife and two children, Mr. Puskari suffers recurring flashbacks and frequent nightmares of the event that render him incapable of holding a steady job. Mr. Puskari is most clearly showing signs of obsessive-compulsive disorder. generalized anxiety disorder. posttraumatic stress disorder. survivor resiliency.

Post-traumatic stress disorder

Explanation:

Post-traumatic stress disorder in which a person feels difficult to come out from the panic memories of any accident or terrifying event. So after the accident, the scary memories used to come again and again for several years which results in intense physical and emotional reactions.

So here as the person suffers from recurring flashbacks and frequent nightmares of that terrorist attack which makes him incapable of doing a steady job which shows he his going through post-traumatic stress disorder.  

answer; eat a strict gluten-free diet;