For those who completed primary school only, the mean age of first heroin use was 17 (SD 5.4) years and 19 (SD 6.0) years for those who attended secondary school or above, the difference failed to reach significance (t395 = -1.89, p = .0.56). Participants who completed primary school only, were a mean age of 17 (SD 4.8) years when they first injected heroin and the mean age of first injection for those who attended secondary school and above was 20 (SD 6.3) years (t386 = -2.46, p = .014).
