Our results show that there were no significant differences in effects between PST and UC patients in this population of primary care patients with relatively mild levels of distress. The cost difference between PST and UC was substantial, but not statistically significant. Cost-effectiveness planes and acceptability curves show that PST was cost-effective in comparison with UC. Indirect costs in the PST group were substantially lower than in the UC group and were the greatest contributor to the difference in total costs. However, this difference was mainly caused by 3 outliers in the UC group. Sensitivity analyses confirmed the small differences in effects and that costs in the PST group were substantially lower than in the UC group. Based on these analyses, PST was also considered cost-effective in comparison with UC in this study. Analyses from the NHS perspective suggested that PST is not considered cost-effective in comparison with UC.
UC patients had significantly lower utility scores at baseline than PST patients. Therefore, we suspect that morbidity rates in the UC group were higher than in the PST group. This may also explain the higher costs in the UC group. Additional analyses showed that the differences in direct and indirect costs were only partially explained by the difference in utility score at baseline (data not shown).
One of the strengths of this trial is that it was a pragmatic trial, meaning that we tried to resemble daily clinical practice as much as possible. By applying as few restrictions as possible on patient selection, we think we succeeded in recruiting a population that is representative of the patients with mental health problems seen by the GP. Also, we tried to model the GP’s normal care process as much as possible. Therefore, the results of this study are likely to be generalisable to the rest of The Netherlands and other countries with similar health care systems.
Research suggests that a considerable part of lost productivity costs in mental disorders is caused by presenteeism
[36, 37]. Therefore, another important strength of this study is that both costs of absenteeism and presenteeism (being present at work, but at reduced work performance) were included, whereas earlier studies included only costs of absenteeism
Our study also has some limitations. First, our study was underpowered to detect relevant cost differences which is reflected in the wide confidence intervals around the cost differences. This is a common problem in economic evaluations alongside clinical trials. Because of the heavily skewed distribution of cost data, very large numbers of patients are needed to detect relevant cost differences
. Second, the number of patients that did not return all cost questionnaires was considerable (PST group 36%, UC group 25%). However, there were no significant differences between patients with and without complete cost data, reducing the chance of bias caused by selective drop-out. Moreover, both the results of the imputed analysis and the complete case analysis showed that PST is cost-effective in comparison with UC. Finally, the follow-up period of the trial may have been too short. If PST indeed is beneficial in comparison with usual care, then it is reasonable to assume that these benefits extend over many years.
Our results can be compared with two other studies that included an economic evaluation of PST for primary care patients with mental health problems
[15, 16]. Our results are consistent with their findings that PST is not effective in comparison with usual GP care. These studies showed that PST was associated with higher costs than usual GP care, while in our study lower costs were found in the PST group. Possible explanations for this discrepancy include the length of the follow-up (9 months in this study versus 6 months in the other studies), the higher costs of the PST in the other studies, and the cost categories that were included.
The accompanying clinical trial showed in a post-hoc analysis that a sub-group of more severely depressed patients could benefit from PST
. This is in line with earlier research
[13, 14]. A recent review showed that PST is more effective in comparison with GP care for depression, and mixed anxiety and depression
. Thus, it is reasonable to assume that PST should be reserved for patients with more severe mental health symptoms. A potential fruitful avenue is the development of stepped care approaches in which PST is offered to patients who do not recover or deteriorate during a period of ‘watchful waiting’.