Sick leave due to common mental disorders (CMDs) increase rapidly and present a major societal challenge. The overall effect of psychological interventions to reduce sick leave and symptoms has not been sufficiently investigated and there is a need for a systematic review and meta-analysis of the field. The aim of the present meta-analysis was to calculate the effect size of psychological interventions for CMDs on sick leave and psychiatric symptoms based on all published randomized controlled trials. Methodological quality, the risk of bias and publication bias were also assessed. The literature searches gave 2240 hits and 45 studies were included. The psychological interventions were more effective than care as usual on both reduced sick leave (g = 0.15) and symptoms (g = 0.21). There was no significant difference in effect between work focused interventions, problem-solving therapy, cognitive behavioural therapy or collaborative care. We conclude that psychological interventions are more effective than care as usual to reduce sick leave and symptoms but the effect sizes are small. More research is needed on psychological interventions that evaluate effects on sick leave. Consensual measures of sick leave should be established and quality of psychotherapy for patients on sick leave should be improved.

Canada thistle is resilient to many control tactics, especially in undisturbed sites. Such sites are suitable for slow acting biological control agents, such as the bacterium Pseudomonas syringae pv. tagetis (PST), because complete control is usually not required in the short term. A new method of introducing or intensifying PST infection of Canada thistle was investigated. Sap of naturally infected Canada thistle was extracted and applied in water plus Silwet L-77 organosilicone surfactant with a backpack sprayer to healthy Canada thistle plants in the field. Application variables of time of the season, spray volume, concentration, and frequency were studied. When practical field rates were applied, infected sap concentration and spray volume did not affect the level of disease observed. This suggests that PST applications could be practical at the field scale because a single application caused apical chlorosis. However, multiple applications proved beneficial because four consecutive weekly applications caused greater disease incidence (50%) than one or two applications (28% and 30%, respectively). Disease symptomology was greatest when PST was applied in mid-July rather than mid-June or mid-August. However, the levels of disease expression were not adequate to effectively suppress Canada thistle. Increased toxin production, either by finding ways to support higher PST populations or by selecting strains that produce more toxin per bacterial cell, would improve this system.