Table 4

Analysis of the relative excess risk (RERI) due to interaction between self-harm and cannabis, drug and alcohol use, risk perception risky driving and sensation seeking

	Any crash		Single vehicle crash
	RERI	P value	RERI	P value
Cannabis use × self-harm*	−0.47 (–1.21–0.28)	0.22	−1.74 (–3.58–0.11)	0.07
Drug use × self-harm†	0.22 (–1.12–1.56)	0.75	−0.13 (–0.64–0.38)	0.62
Alcohol consumption × self-harm‡	0.16 (–0.22–0.54)	0.40	0.31 (–0.69–1.30)	0.54
Risky driving × self-harm§	0.17 (–0.29–0.63)	0.47	0.58 (–0.38–1.55)	0.24
Sensation seeking × self-harm¶	0.22 (–0.24–0.67)	0.35	0.87 (0.07–1.67)	0.03
Risk perception × self-harm**	0.28 (-0.10–0.66)	0.15	0.45 (-0.55–1.44)	0.38

The DRIVE study, NSW, Australia, June 2003–December 2004.
*Cannabis use 2–3 or 4+ times per week per week × self-harm.
†Drug use 2–3 or 4+ times per week per week × self-harm.
‡Alcohol consumption >6 drinks per week × self-harm.
§Highest risky driving tertile × self-harm.
¶Highest sensation seeking tertile × self-harm.
**Highest risk perception tertile × self-harm.
NSW, New South Wales.