Table 2 Study location, inclusion criteria, method of randomization and sample size.

Katon 1996 [16]

• Puget Sound, USA

• Adults (18–80 yrs) considered by the GP as having "definite or probable major depression" were referred to the study over a one-year period and screened using the Symptom Checklist (SCL-20). Participants scoring >= .75 and who were willing to take anti-depressant medication were recruited into the study. Some exclusion criteria were applied. 74.1% were female.

• Stratified (by SCL-20) with randomization of individual patients in blocks.

• Usual Care (UC) n = 76 vs Collaborative Care Intervention (I) n = 77.

Mann 1998. [17]

• UK-wide.

• Adults (18–74 yrs) considered by the GP to have had depression for at least 4 weeks (regardless of prior treatment) were recruited into the study over a 2.5 year period (no further screening was undertaken). Some exclusion criteria were applied. 78% were female.

• Simple randomization of individual patients.

• Usual Care (UC) n = 148 vs Feedback & Nurse Monitoring Intervention (I) n = 271.

• Note – Two interventions were conducted. Only the one meeting criteria for a system intervention is included here.

Katon 1999. [18]

• Puget Sound, USA.

• Adults (18–80 yrs) receiving a new anti-depressant prescription (i.e., no prescription in past 120 days) for anxiety or depression were identified by clinic databases. Screening was conducted 6–8 wks later to select for those with persistent symptoms of depression (as defined by Structured Clinical Interview for DSM-III-R (SCID) > 4 symptoms of depression, and Symptom Checklist (SCL-20) >1, or SCID<4 symptoms of depression but SCL-20>1.5). Some exclusion criteria were applied. 74.5% were female.

• Stratified (by SCL-20) randomization of individual patients in blocks.

• Usual Care (UC) n = 114 vs Stepped Collaborative Care Intervention (I) n = 114.

Katzelnick 2000. [19]

• Wisonsin, Washington and Massachusetts, USA.

• Adults (25–63 yrs) who were "high utilizers" of health clinic (ie, frequency of ambulatory visits above the 85^th percentile) were identified on clinic databases. Eligible participants were screened for major depression or major depression in partial remission using the Structured Clinical Interview for DSM-IV (SCID). Patients meeting second-stage screening criteria on Hamilton Depression Rating Scale (Ham-D; scores = >15) were enrolled. Participants were not on anti-depressants at baseline. Some exclusion criteria were applied. 77% were female

• Cluster randomization by practice.

• Usual Care (UC) n = 189 vs Depression Management Program (I) n = 218.

Simon 2000. [20]

• Puget Sound, USA

• Adults (age range not reported) receiving a new prescription for anti-depressants (i.e., no prescription in past 120 days) were identified by clinic databases and recruited into the study. No further screening was undertaken. Some exclusion criteria were applied. Aprox. 72% were female.

• Stratified (by clinic) with randomization of individual patients.

• Usual Care (UC) n = 196 vs Feedback and Care Management Intervention (I) n = 196.

• Note – Two interventions were conducted. Only the one meeting criteria for a system intervention and is included here.

Wells 2000 [21,29,39]

• 7 regions in the USA.

• Consecutive adults (18+yrs) attending clinics over a 5–7 month period were screened for probable or persistent depression using the Composite International Diagnostic Interview (CIDI – 2 weeks of depressed symptoms or probable depression in the past year, with at least one week of depression in the past month). Some exclusion criteria were applied. 71% were female. 30% of participants were Hispanic (deliberate choice of practices to oversample for Mexican Americans).

• Cluster randomisation (by practice), matched in blocks of 3 on patient demographics, clinician specialty and distance to mental health providers. Stratification by proportion of Mexican American patients occurred in one region only.

• Usual Care (UC) n = 443 vs Quality Improvement-Therapy (I-Therapy) n = 489 vs Quality Improvement-Medication (I-Meds) n = 424.

Rost 2000 [22,27,30,40,41]

• Clinics across the USA.

• Consecutive adults (18+yrs) attending clinics for routine-length visits were screened over an 18 month period for "probable major depression" on the WHO-Composite International Diagnostic Interview (CIDI – 2 weeks of depressed symptoms or probable depression in the past year, with at least one week of depression in the past month). Those meeting second-stage screening criteria on the Inventory to Diagnose Depression (IDD >5 of 9 depression symptoms in previous 2 weeks) were enrolled. Some exclusion criteria were applied. 84% were female.

• Cluster randomization (by practice), matched in blocks (metro vs rural practices) on proportion of patients receiving guideline-concordant care.

• Usual Care (UC) n = 240 vs Enhanced Care Intervention (I) n = 239

• Recovery was only reported for sub-groups of Rost's 2001 sample, in later publications.

• Smith 02 – Exclusion of n = 96 elderly (65+) from Rost 2001 sample. 81% were female. Usual Care (UC) n = 195 (insured n = 150, uninsured n = 45) vs Enhanced Care Intervention (I) n = 188 (insured n = 140, uninsured n = 48).

• Rost 2002 – Exclusion of n = 268 "treatment resistant" participants from Rost 2001 sample. 84% were female. Usual Care (UC) n = 96 vs Enhanced Care Intervention (I) n = 115

Datto 2003 [23]

• Pennsylvania, USA

• Adults (age range not reported) with "symptoms suggestive of depression" were identified by the GP and recruited into the study (no further screening was undertaken). Some exclusion criteria were applied. 60.7% were female.

• Cluster randomisation (by practice).

• Usual Care (UC) n = 31 vs Telephone Disease Management Intervention (I) n = 30.

Finley 2003 [26]

• California, USA.

• Adults (age range not reported) were referred to the study by their primary care provider (GP) when starting new antidepressant medication (ie, no medication taken in past 6 months) for depression (no further screening was undertaken). Some exclusion criteria were applied. Patients were paid $20 at end of study. 85% were female

• Simple randomization of individual patients.

• Usual Care (UC) n = 50 vs Collaborative Care Intervention (I) n = 75.

Capoccia 2004 [24,42],

• Seattle, USA (academic clinic)

• Adults (18+) with a newly diagnosed depression episode and anti-depressant prescription (as determined by their health care provider) were referred to the study, then screened for depression using PRIME-MD (cut off criteria not reported). Some exclusion criteria were applied. 57% were female.

• Simple randomization of individual patients.

• Usual Care (UC) n = 33 vs Enhanced Care Intervention (I) n = 41

Dietrich 2004 [25] [43]

• Clinics across the USA

• Adults 18+ who were commencing or changing treatment for depression were identified by clinicians and referred for a structured interview. Those with DSM-IV major depression or dysthymia, and with Hopkins Symptom Checklist-20 >= 0.5 were eligible. Participants had to be willing to take anti-depressant treatment or be referred for psychological counselling. Some exclusion criteria were applied. 80% were female.

• Cluster randomization (by practice), stratified by health care organisation, and matched by GP specialty, presence of clinic mental health care and distance from the organisations central office.

• Usual Care (n = 181) vs Quality Improvement Intervention (I) n = 224