BEHAVIOURAL DISORDERS. Failure to Thrive (FTT) Definition: Failure to thrive (FTT) is a condition where an infant or child has inadequate growth due to insufficient calorie intake, absorption, or excessive expenditure. Causes: Signs and Symptoms: Management: Diarrhea Definition: Diarrhea is the passage of loose or watery stools at least three times in 24 hours. Causes: Signs and Symptoms: Management: Tonsillitis Definition: Inflammation of the tonsils, commonly caused by viral or