Even if you hate Facebook, you may have realized that it’s just impossible to stop using Facebook. You may have thought there was something severely wrong with you, but it turns out it’s just science.

Researchers from Cornell University in the United States have identified four key reasons why people just can’t resist the urge to log in and use Facebook, regardless of any pledges they’ve made to themselves, friends, or family to stay the heck off the social media network.

The researchers, in a study published on December 3, looked at more than 5000 surveys completed by participants in the project 99 Days of Freedom. This project challenges users to give up Facebook for 99 days or longer.

The project issued surveys on days 33, 66, and 99 of their commitment to gauge people’s moods. Some of the data that came back were very enlightening to the researchers, and they were able to compile some reasons why people can’t stay away.

The first is perceived addiction. So-called “Facebook addicts” who felt they were addicted to it were more likely to go back. One participant stated, “In the first ten days, whenever I opened up an internet browser, my fingers would automatically go to ‘f’.”

The second reason is surveillance. Users who enjoyed using the platform to manage others’ perceptions of them or look in on others were more likely to return. Interestingly, people who were concerned about privacy issues with Facebook were less likely to go back to the site.

The third reason is the mood. If participants were happy, they were much less likely to go back to the site. Another study also found this correlation. The Happiness Research Institute in Denmark published findings last month, showing that Facebook users are 39% more likely to experience feelings of unhappiness compared to those who don’t use it.

The final reason is other social media use. It seems that those who use other social media sites, such as Twitter or Instagram, were also less likely to return to Facebook. It appears that those able to get their social media fix elsewhere don’t necessarily find themselves as likely to need the site.

Eric Baumer, who authored this study, commented on it, saying, “These results show just how difficult daily decisions about social media use can be. In addition to concerns over personal addiction, people are reluctant about corporations collecting, analyzing and potentially monetizing their personal information.”