How Effective are Behaviour Change Interventions?

Contents:

1. How do we measure effectiveness?

2. How effective is medical therapy?

3. How effective are psychological therapies?

“Effect Size”

• A standardized statistic to show the impact of treatments

• (Mean result for treatment group – mean for controls) / standard deviation

Interpretation:

• An effect size of 0.5 represents a success rate of 65% in the treatment group, and 35% in the control group (“success” = score above overall median)

• An effect size of 0.2 suggests 55% versus 45%

Effect Sizes for Selected Medical Interventions

Mean Intervention Outcome effect sizeBypass graft surgery angina 0.80ECT depression 0.80AZT for AIDS mortality 0.47Drug treatment for hyperactivity behavior 0.47 to 0.96Drug treatment for arthritis pain, QoL 0.45 to 0.77Dipyridamole angina 0.24Aortocoronary bypass surgery mortality 0.15Drug therapy for hypertension quality of life 0.11 to 0.28Chemotherapy for breast cancer mortality 0.08 to 0.11

How Effective are Psychological & Behavioral Treatments?

meanIntervention # studies effect size

General Psychotherapy 1231 0.79

Behaviour Modification 953 0.53

Family & Marital Counselling 295 0.55

Treating Juvenile Delinquents 871 0.29

Meditation & Relaxation 289 0.54

Biofeedback & Relaxation 109 0.65

Smoking Cessation 125 0.55

Psychological Treatment for Pain 219 0.90

Source: Lipsey MW, Wilson DB. The efficacy of psychological, educational, and behavioral treatment. American Psychologist 1993;48:1181-1209.