New York: Mothers with a history of depression are not physiologically "in sync" with their children and this may lead to conflicts in their relations, a study has found. The findings indicate that children and the mothers who were sad during the interaction were more likely to be "out of sync" with one another. While interacting, sometimes you just feel like you're in sync with somebody and you know that the interaction is going really well and you're enjoying the conversation. "We're trying to figure out, at the body level, in terms of your physiology, do you see this synchrony in moms and their kids and then how is that impacted by depression?" said Brandon Gibb from Binghamton University in the US. The study, published in the Journal of Child Psychology and Psychiatry, measured heart rate variability -- a physiological measure of social engagement -- in children aged 7-11 and their mothers (44 with a history of depression and 50 with no such history) while they engaged in positive and negative discussions. In the first discussion, mother-child pairs planned a dream vacation together and in the second, they addressed a recent topic of conflict between them -- homework, using the TV or computer, being on time, problems at school and lying, etc. The results indicate that mothers with no history of depression displayed physiological synchrony -- similar increases or decreases in heart rate variability -- with their children during negative discussion. "We found that mothers who had no history of depression were really matching their children's physiology in the moment," said lead study author Mary Woody. "In mothers with a history of depression, we're seeing the opposite. They actually mismatched. As one person is getting more engaged, the other person is pulling away. So they were walking away from the discussion feeling sad," Woody added. The synchrony during interactions is disrupted at the physiological level in families with a history of maternal depression and may be a potential risk factor for the inter-generational transmission of depression, the authors suggested.