Digit ratio, nicotine and alcohol intake and national rates of smoking and alcohol consumption John T. Manning a,⇑ , Bernhard Fink b a Department of Psychology, University of Swansea, Swansea, UK b Department of Sociobiology/Anthropology, University of Goettingen, Goettingen, Germany article info Article history: Received 15 August 2010 Received in revised form 27 September 2010 Accepted 14 October 2010 Available online 10 November 2010 Keywords: Digit ratio 2D:4D Intake nicotine and alcohol National rates smoking and alcohol intake abstract The intake of nicotine (mainly through smoking) and alcohol has public health consequences. However, it is unclear whether all factors that affect individual and national rates of consumption are known. Prena- tal testosterone (PT) may influence smoking and alcohol choices through effects on personality. Thus, morphological markers of PT may correlate with smoking and/or alcohol intake choices. Here we examine the relationship between individual values and national means of 2D:4D, a putative negative correlate of PT, and intake of nicotine and alcohol in a large sample of men and women, i.e. the BBC Internet Study. High intake of nicotine was related to high 2D:4D and high intake of alcohol with low 2D:4D. These find- ings were independent of sex, age, height, education, and individual choices regarding nicotine or alcohol intake. National means of 2D:4D were positively correlated with number of cigarettes consumed per nation after the removal of the effects of gross domestic product (GDP), average height and consumption of alcohol. Alcohol consumption correlated negatively with national 2D:4D after the influence of GDP, average height and consumption of cigarettes per nation were removed. We conclude that PT may have organising effects on smoking and alcohol intake choices. Ó 2010 Published by Elsevier Ltd. 1. Introduction The consumption of nicotine (mainly by smoking) and alcohol has major public health implications (WHO, 2008). Thus, smoking and alcohol consumption have been implicated in the etiology of a number of cancers, including carcinoma of the mouth, esophagus and lung. Smoking is also a leading cause of cardiovascular disease and chronic pulmonary obstructive disease and alcohol can lead to liver disease and hypertension. In 2004 total tobacco-attributable deaths were 5.4 million and are projected to rise to 8.3 million by 2030 (WHO, 2008, 2009). While the health risks associated with smoking and alcohol consumption are clear, the factors that influence individual deci- sions as to patterns of smoking and alcohol consumption are less well understood. Nicotine is a stimulant that releases glucose from the liver and adrenaline from the adrenal medulla and it has both neuroprotective and neurotoxic effects (Ferrea & Winterer, 2009). In many ways alcohol has opposing influences in that it has depressant effects with anxiolytic, hypnotic and sedative actions (Brust, 2010). Smoking and alcohol consumption are inter-linked, given that smoking is a risk factor for alcohol use and alcohol use is a risk factor for smoking (Lajtha & Sershen, 2010). This link is puzzling as the two drugs have opposing effects on such things as locomotion, acetylcholine metabolism and the synthesis of tes- tosterone (T) (English et al., 2001; Lajtha & Sershen, 2010; Ward et al., 2003). In addition, there are sex differences in the intake of both alcohol and nicotine that are widespread across cultures (Bauer, Gohlmann, & Sinning, 2006; Wilsnack et al., 2000), which suggests a biological influence on alcohol and smoking choices. Here we consider the possibility that smoking and alcohol choices are influenced by levels of prenatal testosterone (PT). In order to do this we consider associations between second to fourth digit ratio (2D:4D; a putative negative correlate of PT) and smoking and alco- hol choices. Digit ratio is sexually dimorphic, with males (on average) having lower values of 2D:4D than females. It is thought that 2D:4D is fixed in utero at the end of the first trimester of fetal development and is negatively correlated with PT (Breedlove, 2010; Manning, 2002, 2008; Manning, Scutt, Wilson, & Lewis- Jones, 1998; McIntyre, 2006; Lutchmaya, Baron-Cohen, Raggatt, Knickmeyer, & Manning, 2004). There is evidence that maternal exposure to smoking and to alcohol have influences on 2D:4D in the fetus. Thus, women who smoked during their pregnancies had boys with lower 2D:4D (more ‘‘masculine”) than boys whose mothers did not smoke, although this effect did not extend to daughters (Rizwan, Manning, & Brabin, 2007). In rats, prenatal 0191-8869/$ - see front matter Ó 2010 Published by Elsevier Ltd. doi:10.1016/j.paid.2010.10.016 ⇑ Corresponding author. Address: Department of Psychology, University of Swansea, Swansea SA2 8PP, UK. E-mail address: j.manning@swansea.ac.uk (J.T. Manning). Personality and Individual Differences 50 (2011) 344–348 Contents lists available at ScienceDirect Personality and Individual Differences journal homepage: www.elsevier.com/locate/paid