Background. Routine use of standardized outcome measures within adult mental health services is compulsory in many countries, but not common in clinical practice. As well as political and professional factors, one reason may be that there is little empirical evidence of benefit for patients. It is therefore important to identify predictors of response. Pre-morbid intellectual functioning has predicted response to other interventions. This paper tests the hypothesis that pre-morbid IQ impacts on the effectiveness of routine assessment and feedback of outcome measures.

Method. The Feedback of Outcomes to Users and Staff (FOCUS) single-blind randomized controlled trial (RCT) investigated routine completion and feedback of outcome measures for 160 (101 intervention, 59 control) adult mental health service patients in Croydon, South London (International Standard RCT Number 16971059).

Results. Patients in the top quarter (pre-morbid IQ>110) differentially improved in patient-rated unmet need (adjusted difference 3·4, 95% CI 0·8 to 5·9, p=0·012) and in the top half (pre-morbid IQ>99) in quality of life (adjusted difference −0·6, 95% CI −1·1 to −0·1, p=0·02). The top quarter result remained when controlling for the influence of baseline (p=0·004) and baseline plus follow-up variables (p=0·047).

Conclusions. Feedback of routine outcome measures may improve outcome for patients with higher pre-morbid IQ. There is a need to understand more how routine outcome information is used by staff and patients to inform care. If the goal of routine use of outcome measures is to benefit patients directly, then targeted policies are required.