In a recent article by Weston, Hill, and Jackson (2014) the authors find that personality traits, such as neuroticism, conscientiousness, and openness can actually predict the development of new diseases (in the past, it has only been shown that such personality traits correlate with certain diseases - suggesting that they may be caused by the disease or some other factor that causes both the disease and the personality trait). The authors in this study use a longitudinal data set of older adults and to look at seven common diseases: diabetes, hypertension, lung disease, cancer, heart disease, stroke, and arthritis. Participants were limited to individuals who had visited a doctor at least once in the last two years (to avoid the possibility of undiagnosed diseases), leaving approximately 7,000 participants. Of these, the authors only evaluated those who had no disease at the beginning of the study period (2006) so they could test whether measured personality traits actually predicted the onset of disease by the end of the study period (2010). All analyses controlled for age, race, gender, and marital status.
The authors find that neuroticism, in general, leads to an increase in the probability of being diagnosed with a disease. For example, a one-unit increase on the neuroticism scale (a measure that ranged from 1 to 4) leads to a 24% increase in the odds of being diagnosed with heart disease; a 29% increase for lung disease diagnosis; a 37% increase for high blood pressure; and a 25% increase for arthritis (which just added four more things to every neurotic's list of things to worry about). Interestingly, neuroticism (or any other personality trait for that matter) does not predict the likelihood of getting cancer. So why does neuroticism predict negative health outcomes? The mechanism has been less explored, but the authors postulate that feeling negative emotions reduces the body's immune system, thus making a neurotic person more susceptible to disease.
In a related study published in JPSP, authors Jeronimus, Riese, Sanderman, and Ormel (2014), find that major life events are responsible for approximately half of the variance in neuroticism, but at the same time, neuroticism also predicts these life events. In other words, neurotics are stuck in a infinite loop of terrible (negative life events cause neuroticism which, in turn, causes more negative life events). If that wasn't bad enough, the authors also find that the effects of a negative life experience on neuroticism can last over a decade. Moreover, these findings suggest that neuroticism can change over the course of an individual's lifetime, given that major environmental changes also occur. It should be noted that the effect of life events on neuroticism levels is smaller than the effect of neuroticism on life events (thus, a lot of bad experiences will not make you a neurotic, but likely means you already are one).
Relating this second article back to the first one, both studies show that neuroticism predicts negative health outcomes (assuming that negative life events include bad health). Again, suggesting that there is the potential to use the identification of neuroticism and other personality traits to help manage disease. Unfortunately, the second study's findings that life events have a smaller effect on changes in neuroticism does suggest that preventative actions for neurotic patients may not be very helpful or effective. So, we can identify who may be more likely to suffer a disease but we can do little to change that outcome. Ultimately, unless we can find a way to "cure" neuroticism, we may be able to do little to help people with this trait.