Table 1. Cancer-related PTSS and severe PTSS among women treated for primary breast cancer at 3 and 15 months post surgery.

IES (cancer related)	3 Months post surgery	15 Months post surgery
N	3318	2912
Intrusive thoughts	Mean (s.d.): 10.1 (8.9)	Mean (s.d.): 7.8 (7.9)
	Median: 8	Median: 5
	Range: 0–35	Range: 0–35
	10–90 percentile 0–23	10–90 percentile 0–20
Avoidance	Mean (s.d.): 10.0 (8.8)	Mean (s.d.): 8.4 (8.7)
	Median: 8	Median: 6
	Range: 0–40	Range: 0–40
	10–90 percentile 0–23	10–90 percentile 0–21
IES total (PTSS)	Mean (s.d.): 20.1 (15.9)	Mean (s.d.): 16.2 (15.3)
	Median: 17	Median: 12
	Range: 0–75	Range: 0–71
	10–90 percentile 1–43	10–90 percentile 0–39
Severe PTSS: IES scores ⩾35 indicating severe symptomatology	666 (20.1 %)	415 (14.3%)

Abbreviations: IES=impact of event scale; PTSS=post-traumatic stress symptom.