Children whose mothers are depressed are known to be more at risk of depression themselves. The way people react to the world around them is thought to be important in whether they develop depression or not and interpreting people's facial expressions is thought to be one of the most important factors in this. This American study of 85 girls between the ages of 9 and 14 compared 50 girls whose mothers had no depression with 35 girls whose mothers had had depression. None of the girls had had depression themselves. The girls were asked to judge emotions based on a subtly-changing computer image. The better the girls were at judging emotion the quicker they could work out what the expression was as it moved from neutral to happy, sad or angry. The daughters of the depressed mothers needed a bigger change before they could tell what the expression was and made more errors identifying angry expressions suggesting that this cognitive bias is one way in which depression can be 'transmitted' from mothers to children.
Joormann, Jutta, Gilbert, Kirsten and Gotlib, Ian H. - Emotion identification in girls at high risk for depression Journal of Child Psychology and Psychiatry May 2010, 51(5), 575-582