Almost 15 per cent of preschoolers have abnormally high levels of depression and anxiety, and a difficult temperament at five months of age is the most important early warning sign, a study has found.
Highly strung or tense four and five-year-olds are also more likely to have mothers with a history of depression than children who are not anxious or depressed.
Symptoms could be identified in infants who were fearful or anxious, worried, not as happy as other children or who had difficulty having fun.
The study, published in the Journal of Child Psychology and Psychiatry, was based on annual interviews with 1759 mothers about their children's behaviour from five months to five years of age.
The team of Canadian, French, US and British researchers from the International Laboratory for Child and Adolescent Mental Health Development said depression and anxiety symptoms could be identified in infants who were fearful or anxious, worried, not as happy as other children or who had difficulty having fun.
Difficulties in sleep, changes in appetite or concentration, lack of interest in things they used to find pleasurable and suddenly aggressive behaviour are also early warning signs.
The lead author, Sylvana Cote, a professor at the University of Montreal's department of social and preventive medicine, said: ''As early as the first year of life, there are indications that some children have more risks than others to develop high levels of depression and anxiety.''
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