Eleven RCTs were included (n=2,364). Sample size ranged from 45 to 747.
Study quality was generally high; all studies scored 6 or more out of 11 for validity. Six studies met all criteria for SDM intervention. None of the studies directly assessed the quality of the SDM intervention.
Five studies reported no statistically significant difference in outcomes between intervention and control groups. All of these studies involved patients with physical health care needs and all involved only one session or measurement after a single consultation. One study reported no short-term effect, but reported a positive long-term effect.
One of seven studies assessing patient satisfaction reported a positive intervention effect. This study involved SDM as part of a treatment programme; other studies involved only one SDM session or measurement after a single consultation.
Two of five studies assessing psychological and physical well being reported a positive intervention effect. These studies involved patients making longer term decisions and/or with chronic conditions and longer durations of interventions.
One study reported significantly increased adherence to antidepressant medication at nine to twelve months follow-up among patients exposed to the SDM intervention.
Two of three studies assessing patient knowledge reported significantly higher levels of knowledge in SDM groups; the third study reported significantly greater knowledge in the control group.
Both studies of patients with mental health problems reported positive outcomes in intervention groups.