Existing literature has established that loneliness, characterized by a sense of emptiness, worthlessness, and a lack of control, is negatively associated with well-being. Moreover, self-rated health, a subjective evaluation of one’s current health status, has also been pointed out as an important predictor of well-being, due to its high proportion of shared variance with well-being.
The correlation between two variables can reflect reverse causation or unobserved factors that influence both. Mendelian Randomization (MR) can be used to get a better hold on causality by estimating the causal effect of a risk or protective factor on an outcome, provided that genetic variants are known that influence the risk factor.
In order to answer questions like: “Do lonely people become unhappy or is unhappiness the driver for a lonely life”, or “are people happy because they are healthy or the other way around”, we will apply an MR approach. We will use the summary statistics of large Genome-Wide Association Studies for well-being (Baselmans et al., 2018), loneliness (Abdellaoui et al., 2018), and self-rated health (Harris et al., 2017) and conduct two sample bidirectional MR analyses to establish whether well-being affects loneliness and/or self-rated health, or vice versa.