Donna Gillies, Penny Buykx, Alexandra G Parker, Sarah E Hetrick

Approximately 25% of people will be affected by a mental disorder at some stage in their life. Despite the prevalence and negative impacts of mental disorders, many people are not diagnosed or do not receive adequate treatment. Therefore primary health care has been identified as essential to improving the delivery of mental health care. Consultation liaison is a model of mental health care where the primary care provider maintains the central role in the delivery of mental health care with a mental health specialist providing consultative support. Consultation liaison has the potential to enhance the delivery of mental health care in the primary care setting and in turn improve outcomes for people with a mental disorder. To identify whether consultation liaison can have beneficial effects for people with a mental disorder by improving the ability of primary care providers to provide mental health care. We searched the EPOC Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL), and bibliographic databases: MEDLINE, EMBASE, CINAHL and PsycINFO, in March 2014. We also searched reference lists of relevant studies and reviews to identify any potentially relevant studies. We included randomised controlled trials (RCTs) which compared consultation liaison to standard care or other service models of mental health care in the primary setting. Included participants were people attending primary care practices who required mental health care or had a mental disorder, and primary care providers who had direct contact with people in need of mental health care. Two review authors independently screened the titles and abstracts of identified studies against the inclusion criteria and extracted details including the study design, participants and setting, intervention, outcomes and any risk of bias. We resolved any disagreements by discussion or referral to a third author. We contacted trial authors to obtain any missing information.We collected and analysed data for all follow-up periods: up to and including three months following the start of treatment; between three and 12 months; and more than 12 months following the start of therapy.We used a random-effects model to calculate the risk difference (RD) for binary data and number needed to treat for an additional beneficial outcome (NNTB), if differences between groups were significant. The mean difference (MD) or standardised mean difference (SMD) was calculated for continuous data. 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.