Personality types, lifestyle, and sensitivity to mental stress in association with NK activity

We conducted a cross-sectional study among 302 healthy Japanese male worker s to make a mechanistic approach to the association between personality typ es and cancer; two types of personality, the emotionally unstable-introvert and the emotionally stable-extravert, were compared with each other in lif estyle, mental stress status, and biological markers such as plasma levels of neurotransmitters and NK activity of peripheral lymphocytes. We first fo und that emotionally unstable-introverts have a more unhealthy lifestyle as sociated with low NK activity than among stable-extraverts,along with highe r sensitivity to mental stress (also known to suppress NK activity) than st able-extraverts. Second, emotionally unstable-introverts were found to have in fact decreased NK activity along with higher plasma levels of noradrena line, when compared with stable-extraverts. Our results thus demonstrate th at emotionally unstable-introverts have a decreased capacity of immunologic al host defense against cancer, which is possibly due to two factors, unhea lthy lifestyle and high sensitivity to mental stress.