• Bystander responses;
  • diffusion of responsibility;
  • overdose;
  • social factors


Aims  The purpose of this study was to examine individual, social and setting correlates of calling the emergency number, 911, during an overdose.

Design  Cross-sectional survey.

Methods  A sample of 397 current or former drug users in Baltimore, MD, USA who reported having ever witnessed an overdose.

Findings  Participants reported calling an ambulance in 23% of the overdose cases. Results from multivariate logistic regression indicate that having ever overdosed and having four or more bystanders present independently decreased the likelihood of calling 911. Having ever witnessed a fatal overdose and having any female bystanders present increased the likelihood of calling 911. There was a significant interaction between fear of arrest and prior exposure to the police. Setting of the overdose (public versus private) was not associated with calling 911 after controlling for other factors.

Conclusions  These findings suggest that in addition to personal characteristics of witnesses, social factors influence calling 911. Intervention at the social level may be a viable means to increase bystander helping behaviors.