**Longitudinal research** is a research method that follows a subject over a long period of time to observe changes and developments over time. In Japanese, it is also called ‘縦断的調査’ or ‘縦断研究’. **Longitudinal research features**. - **Time-based data collection**: the same subject (e.g. person or group) is observed and measured at multiple times over a period of time. For example, you might conduct a survey every month over a year and record changes. - **Analysis of changes and trends**: records changes over time and is therefore useful for tracking individual or group growth, behavioural changes and trends. - **Commonly used in cohort and panel studies**: often used in cohort studies of specific populations or in panel studies where the same sample is regularly surveyed。 **Benefits and objectives of longitudinal research**. - **Finding causal relationships**: collecting data longitudinally makes it easier to identify change causes and consequences and uncover causal relationships. - **Understanding trends over time**: suitable for understanding growth, behavioral changes, and trends in participants and subjects. For example, it can be used to understand how health and behavioral habits change over time. Longitudinal research is an important method for tracking changes and developments in a subject over time that cannot be captured by instantaneous data collection.