Overthinking is most common in students nowadays after the COVID-19 pandemic in Pakistan. The main reason behind this is due to lockdown or quarantine at home for a long time. The coronavirus infected many people some have died, and this may cause worry and ruminative thoughts that result in mental illness. This research is designed to study the significant exposure of overthinking in which we take five factors related to overthinking. For this purpose, we used a sample of 150 students from different universities in Multan via purposive and snowball sampling. The variables of the study are Rumination, Depression, Brooding, Worry, and the Mental health of the students. These were measured on the Likert scale through the questionnaire. The findings concluded that there is a positive correlation among all the variables of the study. From the correlation matrix, we see that mental health is strongly correlated with rumination and worry. Mental health is one of the causes of overthinking, it is used as a dependent variable in this study. Furthermore, a multiple linear regression model is used to check the effect of rumination, brooding, depression, and worry on mental health. Results show that rumination and worry were the significant exposures for making changes in mental health. The study concluded that as rumination and worry increase, mental health disturbs so which may result in overthinking in the students. This study will be helpful for worldwide students to overcome mental health problem and fight against overthinking during any pandemic.