The scientific evidence on the causes for sick leave attributed to back and neck disorders was reviewed. Categories were established for acute, recurring, and chronic problems based on the duration of the sick leave period. Forty-eight articles were found to be relevant, whereof two were of high quality and 26 were of medium or low quality. Quality was assessed exclusively in relation to the aim of this systematic review. The results reveal limited published research on causes for sick leave from back and neck disorders. The generalisability of the findings is also limited since most of the subjects were men and employees in manufacturing industries. Women, white-collar workers, employees in the public sector (care, social services, schools, etc) were underrepresented in the studies. Hence, these groups and areas should be studied further to verify conclusions and enhance knowledge about the causes for sick leave from back and neck disorders. The following factors were found to have consistent, but limited, support as regards their influence on the risk for sick leave due to back and neck disorders: (a) heavy physical workload, bent or twisted working position, and low work satisfaction increases the risk for short-term and long-term sick leave; (b) specific back diagnoses and previous sick leave due to back disorders increases the risk for short-term and long-term sick leave; (c) female gender, smoking, exposure to vibration, and deficient social support were not found to significantly increase the risk for short-term and long-term sick leave; (d) self-reported pain and functional impairments were associated with a high risk for long-term sick leave; (e) longer employment periods reduced the risk for short-term sick leave; (f) perceived demands at work did not influence short-term sick leave; (g) female gender and higher age increases the risk for disability pension.