Functional Family Therapy (FFT) is a family-based intervention for youth with behaviour problems. It is often described as an evidence-based programme with consistent, positive effects. This systematic review finds that FFT does not produce consistent benefits or harms. The positive or negative direction of results is inconsistent within and across studies.

What is this review about?
FFT is a prominent, short-term treatment for families of youth with behaviour problems that has been implemented in 45 states in the USA and in nine other high-income countries.Proponents claim that FFT is consistently more effective than treatment as usual (TAU) and other treatments in improving outcomes for youth and families. This review assessed the effectiveness of FFT in reducing recidivism, out-of-home placements, youth behaviour problems, delinquency, and substance use; and improving peer relations, self esteem, school outcomes, parent functioning, and family functioning.

What is the aim of this review?
This review synthesized data from the best available studies to assess the effectiveness of FFT compared with other active treatments and with no treatment.

What studies are included?
The review included rigorous evaluations of the impacts of FFT, including: randomised controlled trials and non-randomised studies that used parallel cohorts and statistical controls for between-group differences at baseline. Eligible studies involved families of young people aged 11-18 with behaviour problems, such as criminal offenses, delinquency, anti-social behaviour, and substance abuse.

What are the findings of this review?
Twenty studies met the review’s eligibility criteria, but only 15 provided valid data for meta-analysis. All included studies had high risks of bias on at least one indicator. Half of the studies had high risks of bias on at least four indicators, and most (75%) had incomplete reporting of outcomes and endpoints.

The review found that FFT is not consistently more or less effective than the other treatments to which it has been compared, including various forms of TAU and individual, family, and group therapies. There is insufficient evidence to draw conclusions about the effects of FFT compared with no treatment. The direction of FFT effects is mixed, sometimes positive, sometimes negative. Confidence intervals show that almost all pooled estimates of effects of FFT are not statistically different from zero. Prediction intervals indicate that future evaluations of FFT are likely to show a wide range of negative and positive effects.

What are the implications for research and policy?
The best available evaluations of FFT are small controlled trials and quasi-experiments with incomplete reporting of outcomes and some high risks of bias. Future studies should have prospectively registered protocols, use larger samples and more rigorous research methods, and provide full reporting on all outcomes and end points. Incomplete reporting of results of primary studies may have inflated overall estimates of positive effects of FFT. Although FFT has been marketed as a “scientifically proven”, effective, evidence-based practice, policymakers and practitioners should be aware that the certainty of the evidence for FFT is very low. The direction of results is inconsistent within and across studies, and there is no empirical support for claims that FFT is consistently more effective than other treatments. Information on the cost effectiveness of FFT appears to be based on inflated estimates of the effects of treatment. Therefore, claims about the cost effectiveness of FFT are not convincing.