Friendship network. Social network of the adolescents in the first year of upper secondary school in Tromsø in the Tromsø Study: Fit Futures I, where the nodes are coloured by cold-pressor pain tolerance. Orange: pain tolerant. Blue: pain sensitive. White: not measured (non-participants or not tested). The isolates (i.e. individuals with no friendship ties) have been removed to reduce visual clutter. Out of the isolates, there were three pain sensitive individuals and two pain tolerant individuals.