birth
METHODS:       Questionnaires were sent to five consecutive birth cohorts of Finnish 16 year old       twins born in 1975-9 and to their parents (3065 families).
METHODS:       Questionnaires were sent to five consecutive  @SUBJECT$  @PREDICAT$  @OBJECT$  of Finnish 16 year old       twins born in 1975-9 and to their parents (3065 families).