Table 1 Paper quality scoring system on five criteria:

1

Size of the study population of relevance

Range 0–1

2

Power calculation: whether performed or not

Range 0–1

3

Confounding: degree of adjustment for obvious confounders

Range 0, none; 1, age/gender; 2, age/gender and socio-economic indicators

4

Ethnicity definition: whether explicit, accurate and hypothesis based

Range 0, none; 1, a definition; 2, self assigned; 3 rated on basis of self identification and parental origins

5

Deliberate self harm: whether attempts had been made to ensure the episode was an actual self harm

Range 0, none; 1 self report; 2, some attempt at measurement; 3, well defined and measured