During the 1990s, several studies were conducted regarding behavioural and emotional functions in preterm
infants. However, methodological flaws in study designs precluded any firm conclusions regarding these
functions. Flaws included the use of clinical rather than population-based samples, a broad range of gestational
ages in relation to the birthweights of subjects, small sample size, lack of psychometrically sound assessment
tools, lack of controls, and failure to provide information on medical and psychosocial risk factors.