Many politicians believe they can intervene in the economy to improve people’s lives. But can they? In a social experiment carried out in the United Kingdom, extensive in-work support was randomly assigned among 16,000 disadvantaged people. We follow a sub-sample of 3,500 single parents for 5 ensuing years. The results reveal a remarkable, and troubling, finding. Long after eligibility had ceased, the treated individuals had substantially lower psychological wellbeing, worried more about money, and were increasingly prone to debt. Thus helping people apparently hurt them. We discuss a behavioral framework consistent with our findings and reflect on implications for policy.