Scientists annually evaluated a representative sample of pre-schoolers from five months to five years of age. All 1,758 children were born in Quebec and mothers provided information during extensive interviews on behaviour and family members, according to a release.

'We found that lifetime maternal depression was the second most important predictor of a typically high depressive and anxiety problems during pre-school years,' stresses Cote.

'Our study is the first to show that infant temperament and lifetime maternal depression can lead to a high trajectory of depressive and anxiety problems before school entry.'

'It is critical that preventive interventions be experimented with infants who risk developing depressive and anxiety disorders,' adds Cote.

The investigation was published in the Journal of Child Psychology and Psychiatry.