Background. There is considerable disagreement about what happens to the risk of anxiety and depression disorders and symptoms as people get older. Methods. A search was made for studies that examine the occurrence of anxiety, depression or general distress across the adult life span. To be included, a study had to involve a general population sample ranging in age from at least the 30s to 65 and over and use the same assessment method at each age. Results. There was no consistent pattern across studies for age differences in the occurrence of anxiety, depression or distress. The most common trend found was for an initial rise across age groups, followed by a drop. Two major factors producing this variability in results were age biases in assessment of anxiety and depression and the masking effect of other risk factors that vary with age. When other risk factors were statistically controlled, a more consistent pattern emerged, with most studies finding a decrease in anxiety, depression and distress across age groups. This decrease cannot be accounted for by exclusion of elderly people in institutional care from epidemiological surveys or by selective mortality of people with anxiety or depression. Conclusion. There is some evidence that ageing is associated with an intrinsic reduction in susceptibility to anxiety and depression. However, longitudinal studies covering the adult life span are needed to distinguish ageing from cohort effects. More attention needs to be given to understanding the mechanism behind any ageing-related reduction in risk for anxiety and depression with age. Possible factors are decreased emotional responsiveness with age, increased emotional control and psychological immunization to stressful experiences.