Abstract: There were 8203 citations identified from database searches and reference lists. We included 12 trials with 2605 consumer participants and more than 905 primary care practitioner participants. Eleven trials compared consultation liaison to standard care and one compared consultation liaison to collaborative care, with a case manager co-ordinating mental health care. People with depression were included in eight trials; and one trial each included people with a variety of disorders: depression, anxiety and somatoform disorders; medically unexplained symptoms; and drinking problems. None of the included trials reported separate data for children or older people. There was some evidence that consultation liaison improved mental health up to three months following the start of treatment (two trials, n = 445, NNTB 8, 95% CI 5 to 25) but there was no evidence of its effectiveness between three and 12 months. Consultation liaison also appeared to improve consumer satisfaction (up to three months: one trial, n = 228, NNTB 3, 95% CI 3 to 5; 3 to 12 months: two trials, n = 445, NNTB 8, 95% CI 5 to 17) and adherence (3 to 12 months: seven trials, n = 1251, NNTB 6, 95% CI 4 to 13) up to 12 months. There was also an improvement in the primary care provider outcomes of providing adequate treatment between three to 12 months (three trials, n = 797, NNTB 7, 95% CI 4 to 17) and prescribing pharmacological treatment up to 12 months (four trials, n = 796, NNTB 13, 95% CI 7 to 50). There was also some evidence that consultation liaison may not be as effective as collaborative care in regards to symptoms of mental disorder, disability, general health status, and provision of treatment. The quality of these findings were low for all outcomes however, apart from consumer adherence from three to 12 months, which was of moderate quality. Eight trials were rated a high risk of performance bias because consumer participants were likely to have known whether or not they were allocated to the intervention group and most outcomes were self reported. Bias due to attrition was rated high in eight trials and reporting bias was rated high in six. There is evidence that consultation liaison improves mental health for up to three months; and satisfaction and adherence for up to 12 months in people with mental disorders, particularly those who are depressed. Primary care providers were also more likely to provide adequate treatment and prescribe pharmacological therapy for up to 12 months. There was also some evidence that consultation liaison may not be as effective as collaborative care in terms of mental disorder symptoms, disability, general health status, and provision of treatment. However, the overall quality of trials was low particularly in regards to performance and attrition bias and may have resulted in an overestimation of effectiveness. More evidence is needed to determine the effectiveness of consultation liaison for people with mental disorders particularly for those with mental disorders other than depression.

Plain-language summary: In this review of studies published up till March 2014, the effectiveness of consultation liaison was compared to standard primary care and other types of mental health care. We included 12 trials with 2605 consumers and more than 905 primary care providers. Consultation liaison was compared to standard care in 11 trials, and compared to collaborative care in one trial. Collaborative care is mental health care co-ordinated by a primary care case manager. There was some evidence that consultation liaison improved mental health, satisfaction with care and adherence to treatment in people with some mental disorders, particularly those with depression, and improved mental health care by primary care providers. There was also some evidence suggesting consultation liaison may not be as effective as collaborative care. However, as the overall quality of trials was low, the effectiveness of these ways of delivering care may have been overestimated. No conclusions can be made regarding the use of consultation liaison with people who have other mental disorders such as schizophrenia or bipolar disorder. There was also no data which could inform practice with specific groups of people such as children and adolescents, and the elderly. More high quality trials of consultation liaison are needed.