PROBLEMS AND SOLUTIONS IN LONGITUDINAL RESEARCH - FROM THEORY TO PRACTICE

Longitudinal studies provide the only method for directly studying the natural course of human growth and development and are therefore inva luable, both to public health and clinical medicine, However, longitud inal studies are accompanied by specific problems. The purpose of this final paper is to discuss in two separate sections some of the method ological, analytical and practical issues regarding the relevance of t he findings reported. Examples of such problems and their solutions ar e described. Methodological issues discussed concern statistical concl usion validity, internal validity and construct validity of longitudin al studies. Practical issues discussed concern the design of longitudi nal studies, the recruitment and retention of subjects, and the method s used. Finally, examples of the significance of longitudinal research outcomes to public health and clinical medicine are given.