Table 2. Comparison of two sets of criteria for post-traumatic stress disorder: DSM-IV (Phase 1) and the alternative set for chimpanzees (Phases 1 and 2).

DSM-IV Criteria		Alternative Criteria
A. The person has been exposed to a traumatic event in which both of the following were present:	(1.) The person experienced, witnessed, or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others.	A.	(1.) Same.
	(2.) The person's response involved intense fear, helplessness, or horror.		(2.) Deleted.
B. The traumatic event is persistently reexperienced in at least one of these ways:	(1.) Recurrent and intrusive distressing recollections of the event, including images, thoughts or perceptions.	B. Reexperiencing. 1 item needed:	(1.) Deleted.
	(2.) Recurrent distressing dreams of the event.		(2.) Deleted.
	(3.) Acting or feeling as if the traumatic event were recurring (includes a sense of reliving the experience, illusions, hallucinations, and dissociative flashback episodes, including those that occur on awakening and when intoxicated).		(3.) Deleted.
	(4.) Intense psychological distress at exposure to internal or external cues that symbolize or resemble an aspect of the traumatic event.		(4.) Emotionally upset by reminders of negative or traumatic events in the past.
	(5.) Physiological reactivity on exposure to external cues that symbolize or resemble an aspect of the traumatic event.		(5.) A physical reaction to reminders of negative or traumatic events in the past (e.g. goose bumps, heavy or irregular breathing).
C. Persistent avoidance of stimuli associated with the trauma and numbing of general responsiveness, as indicated by at least three of the following:	(1.) Efforts to avoid thoughts, feelings or conversations associated with the trauma.	C. Avoidance. 3 items needed:	(1.) Deleted.
	(2.) Efforts to avoid activities, places, or people that arouse recollections of the trauma.		(2.) Avoidance of certain activities, places or types of places, or certain individuals or groups (human or chimpanzee) that may arouse recollections of trauma.
	(3.) Inability to recall an important aspect of the trauma.		(3.) Deleted.
	(4.) Markedly diminished interest or participation in significant activities.		(4.) Lack of interest in play, food, other individuals, or grooming.
	(5.) Feeling of detachment or estrangement from others.		(5.) Social withdrawal.
	(6.) Restricted range of affect.		(6.) Less variability in facial expressions compared with other chimpanzees.
	(7.) Sense of foreshortened future.		(7.) Deleted.
D. Persistent symptoms of increased arousal, as indicated by at least two of the following	(1.) Difficulty falling or staying asleep.	D. Increased arousal. 2 items needed:	(1.) Awake or easily awakened during evening observations, difficulty falling asleep, or excessive sleep.
	(2.) Irritability or outbursts of anger.		(2.) Excessive outbursts, or easily irritated or angered.
	(3.) Difficulty concentrating.		(3.) Poor attention to tasks or difficulty concentrating.
	(4.) Hypervigilance.		(4.) Extremely watchful or “on guard”.
	(5.) Exaggerated startle response.		(5.) Easily startled or jumpy.
E. Duration of symptoms is more than 1 month.		E. Duration of symptoms reported in text using population-based trends.
F. The disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.		F. Deleted.