The study analyzed more than 166,000 California work injury claims for back conditions with no spinal cord involvement and found an association between higher levels of opioid use with higher costs and a higher prevalence of other adverse outcomes such as increased likelihood of lost time from work, delayed recovery and more litigation. The study adds to scientific literature that suggests that at higher levels of use, opioids can have an adverse impact on both activity levels and on self-efficacy, and that prolonged administration of pain medication may impede rather than facilitate injured workers' recovery from occupational back injuries.