Objective: There is a need to explore the beliefs regarding the causes of illegal substance use of the people who themselves use the substances (SU) and their GPs. Increased knowledge about such beliefs--often referred to as causal attributions--may improve mutual understanding and communication between SU and GPs.
Methods: Eight SU and five GPs were interviewed about the causes of illegal substance use. They also talked about how substance use was discussed in consultations. Data were analysed qualitatively.
Results: Both the SU and the GPs believed that several factors usually were important in each case of illegal substance use. The SU more often than the GPs emphasised the positive aspects of illegal substance use. We discerned five main causes: biological, social, lack of self-control, positive experiences, and chance. Several of the SU and GPs emphasised that it was difficult to communicate about substance use.
Conclusion: The GPs and the SU believed illegal substance use is caused by many factors, including biological, social, and lack of self-control. Communicating about illegal substance use is challenging.
Practice implications: GPs should be aware of the clinical importance of causal attributions and should explore beliefs held by SU about the causes of their substance use.