Economic conditions and adversities early in life are known to impact a range of health and cognitive outcomes at high ages. Studies in economics have speculated that the underlying causal pathway involves epigenetic mechanisms affecting gene regulation. We advance on this by identifying causal effects of early-life economic conditions on DNA methylation (DNAm) later in life. Specifically, we examine the extent to which the individual biological age (as predicted by DNAm) deviates from the chronological age. We use the economic business cycle at birth for causal variation in economic conditions early in life. Results based on samples of elderly individuals from five merged UK data sets show strong effects, with unfavourable conditions at birth on average leading to a positive difference between biological and chronological age.