Table 5.

Results of cost-effectiveness analysis at 18 months

	Estimated incremental cost	p value	Estimated incremental QALYs	p value	ICER, £ per QALY
Primary analysis
QALYs	£1266 (736 to 1796)	<0·0001	0·034 (−0·004 to 0·065)	0·13	£36 812
Secondary analysis
Hospital attendance for repeated self-harm event	£1253 (725 to 1780)	<0·0001	0·033 (−0·130 to 0·197)*	0·98	Family therapy less effective and more costly than treatment as usual (family therapy is a dominated option)†
Sensitivity analyses
Bootstrapped average (10 000 replications)‡	£1255 (1149 to 1260)	<0·0001	0·034 (0·034 to 0·034)	0·03	£36 706
Assumption of only one therapist involved in each session in the family therapy group‡	£1380 (748 to 2013)	<0·0001	0·034 (−0·004 to 0·065)	0·13	£40 130
Assumption of average number of therapists involved in each treatment session in the family therapy group‡	£1546 (910 to 2183)	<0·0001	0·034 (−0·004 to 0·064)	0·14	£44 956
Adjustment for baseline EQ-5D-3L differences‡	£1266 (736 to 1796)	<0·0001	0·039 (0·035 to 0·042)	0·03	£32 852
Complete case	£1135 (267 to 2538)	<0·0001	−0·003 (−0·086 to 0·080)	0·91	Family therapy less effective and more costly than treatment as usual (family therapy is a dominated option)
Including caregivers' QALYs‡	£1207 (662 to 1752)	<0·0001	0·058 (0·002 to 0·114)	0·04	£20 808

All results are estimates for family therapy versus treatment as usual (95% CI). QALY=quality-adjusted life-year. ICER=incremental cost-effectiveness ratio.

^*Incremental number of self-harm events estimate (95% CI).

^†ICER, £ per self-harm event.

^‡With multiple imputation.