1 King's College London, Addictions Department, Institute of Psychiatry, Psychology & Neuroscience, 4 Windsor Walk, London SE5 8BB, United Kingdom; UK Centre for Tobacco and Alcohol Studies, United Kingdom. Electronic address: sol.richardson@cantab.net.
2 King's College London, Addictions Department, Institute of Psychiatry, Psychology & Neuroscience, 4 Windsor Walk, London SE5 8BB, United Kingdom; UK Centre for Tobacco and Alcohol Studies, United Kingdom.