The 41 participating schools comprised 35 comprehensive, 4 independent, and 2 grammar schools: nine were single sex (4 male, 5 female). Figure shows the number of eligible and actual participants and the reasons for non-inclusion. Overall, 6020 pupils took part in the study. They recorded their ethnic status as white (4956 pupils), black (169), Asian (671), and other (157); 67 were not known.
Prevalence of deliberate self harm and suicidal ideation
A lifetime history of deliberate self harm was reported by 784 of 5923 (13.2%) pupils. Deliberate self harm in the previous year was reported by 509 (8.6%) pupils, of whom 398 (6.9%) had carried out an act of deliberate self harm meeting study criteria in the previous year (table ). The remainder of the results on deliberate self harm are based on this latter group. In 50 (12.6%) cases self harm had resulted in presentation to hospital. In 179 (45.0%) cases the participants said they had wanted to die. The main methods used for deliberate self harm were cutting (257; 64.6%) and poisoning (122; 30.7%). Hospital referral occurred more often for overdoses (27 of 118; 22.9%) than for cutting (16 of 252; 6.3%; χ2=21.39, P<0.001). Multiple acts of deliberate self harm were reported by 218 of 398 (54.8%) participants who self harmed.
Table 1 Prevalence of deliberate self harm, based on descriptions provided by adolescents, and suicidal ideation in previous year
Suicidal ideation (without deliberate self harm) in the past year was reported by 863 of 5737 (15.0%) pupils (table ). This was more common in females than males (odds ratio 3.1, 95% confidence interval 2.6 to 3.6).
Factors associated with deliberate self harm
Deliberate self harm within the previous year was far more common in females than it was in males (11.2% v 3.2%; odds ratio 3.9, 3.1 to 4.9). Because of interactions of some variables with sex, factors associated with deliberate self harm were analysed separately for males and for females (table ).
Table 2 Association of deliberate self harm with other variables. Values are numbers (percentages) of patients who self harmed unless stated otherwise
Deliberate self harm was less common in Asian than white females. Females living with one parent (whether or not with a step parent) had higher rates of deliberate self harm. For both sexes there was an incremental increase in deliberate self harm with increasing consumption of cigarettes or alcohol and number of times drunk (especially in females). A higher frequency of self harm was associated with all categories of drug use (data not presented). Self harm was more common in pupils who had been bullied and was strongly associated with physical and sexual abuse in both sexes. Although more males than females had been in trouble with the police, an association with deliberate self harm was stronger in females. Awareness of recent self harm by peers was reported more often by females than by males but was associated with self harm in both sexes. A similar association was found with self harm by family members. Pupils of either sex who had recently been worried about their sexual orientation had relatively higher rates of self harm. Levels of depression, anxiety, impulsivity, and self esteem were all associated with self harm in both sexes.
In multiple logistic regression, factors significantly associated with deliberate self harm in the previous year in females were: having friends who had recently self harmed, self harm by family members, drug use, depression, anxiety, impulsivity, and low self esteem (table ). In males, factors associated with deliberate self harm in the previous year were: having friends who had recently self harmed, self harm by family members, drug use, and low self esteem. For both sexes, awareness of peers who had self harmed was the strongest binary factor in the final explanatory model. Figure shows a strong association between being a pupil in a coeducational school who has self harmed and being aware of self harm in peers (r=0.80, P<0.0001), but only in females (r=0.67, P<0.0001; males: r=0.20, P=0.28).
Table 3 Multivariate logistic regression for deliberate self harm in previous year for 88 of 2861 males and 276 of 2308 females
Association between pupils who had deliberately self harmed in previous year and friends who had self harmed; for coeducational schools only