The magnitude of many of the effects described above are not just statistically significant but also clinically significant. In the large Avon Longitudinal Study of Parents and Children population study, it was found that, if the mother was in the top 15% for anxiety, her child was at double the risk for emotional and behavioural problems at ages 4 and 7 years after controlling for a wide range of possible confounders, including postnatal maternal mood.