Post-traumatic stress disorder occurs when a person who has gone through a significant trauma, a life-threatening accident, a natural disaster, or abuse shows stress symptoms that impair the person's ability to function. Psychosomatic disorder is a real, physical disorder that has a psychological cause. Tension headaches have real pain caused by muscle spasm, but stress and anxiety have a role in causing the symptoms. Schizophrenia is a form of psychosis in which there is a loss of contact with reality. MRI and PET scans show brain abnormalities and changes in function. Panic disorder runs in families, but whether it is due to genetics or environment is not clear. Panic disorder is characterized by sudden, brief attacks of intense fear that cause physical symptoms. Epileptic-like activity in the brain is thought to be the cause of intermittent explosive disorder which is characterized by recurrent episodes of aggression toward people or property.

All of these are factors that can contribute to PTSD, except for an on-going chronic physical health condition. On-going mental health conditions, such as depression and anxiety, can contribute to PTSD (usually in combination with more actue problems of experiencing or witnessing trauma), and physical conditions can increase the likelihood of depression, but alone, they do not increase the likelihood of developing PTSD.

Individuals with a panic disorder suffer from sudden, overwhelming and repeated attacks of terror, which can occur out of nowhere. Major changes in behavior and persistent anxiety over having further attacks are characteristic of panic disorders. Often external stimuli or internal thoughts can trigger these attacks.

The other choices are incorrect. The fear of no escape possibilities in crowded situations is considered to be one criteria of agoraphobia, not of panic disorder. The exaggerated fear of specific objects or situations is characteristic for phobic disorders, not of panic disorder. Last, generalized anxiety disorder is marked by the diffuse state of general worries and fears, which are not based on a specific object or event. This is not the best description listed to fit the characteristics for panic disorder.

Agoraphobia occurs when a patient fears situations that make them feel trapped, embarrassed, or helpless. They may fear an actual event or even simply the anticipation of an event. This is more likely to occur in a crowded area, such as a subway or metro bus, than it would simply interacting with a few strangers at a given time. In other words, they may experience a lack of desire to interact with strangers to avoid embarrassment, but that is not a situation in which they would feel trapped or helpless.

Social anxiety disorder is the correct answer. The fear is judged to be out of proportion to the actual risk of the social interactions and is causing significant impairment in occupational functioning, which is concerning for social phobia. Social anxiety disorder should be suspected when intense fear of social interactions, in which the individual may be scrutinized by others, is out of proportion to the actual threat of the social situation and causes significant impairment in important areas of functioning, and the fear is not better explained by some other mental disorder.