Examining proximity exposure in a social network as a mechanism driving peer influence of adolescent smoking

•Proximity exposure: exposure to certain people in social networks based on distance.•Exposure to smokers by proximity (proximity exposure) predicts adolescent smoking.•This prediction persists, even in the absence of friends who smoke.•Peer influence by proximity is a more powerful process than peer selection.•Early proximity exposure predicts later cohesion exposure (befriending smokers).