It has long been known that smoking can increase risk of heart disease, strokes, asthma, emphysema and many forms of cancer. Smoking may also increase the risk of psychological distress as well.
A recent Scottish study reported on psychological health of 5,560 non-smokers and 2,595 smokers. Saliva levels of cotinine- a breakdown product of nicotine were measured as well to determine levels of second hand smoke exposure in non-smokers. Psychological distress- such as depression and anxiety- were highest in the smokers- with 20% of smokers experiencing psychological distress such as depression and anxiety. Among non-smokers- psychological distress occurred in 9% of smokers with low second hand tobacco smoker exposure, 11% of non smokers with moderate smoke exposure and 14% of non-smokers with heavy smoke exposure. Results were adjusted for factors like socioeconomic levels, alcohol and drug use and physical exercise. The nicotine in smoking may have a negative effect on mood.
This study by Hamer et al is published in the August 2010 Archives of General Psychiatry.