Competing interests: PJH has received reimbursement for attending symposiums from Solvay Pharmaceuticals, Bristol-Myers Squibb, and Pfizer Pharmaceuticals and for educational training of family doctors from Bristol-Myers Squibb. JB has received fees from Janssen-Cilag Farmaceutica. If you are interested in being a contributor or peer reviewer for Clinical Evidence please visit the Clinical Evidence website (www.clinicalevidence.org) Clinical Evidence is published by BMJ Publishing Group. The fifth issue is available now, and Clinical Evidence will be updated and expanded every six months. Individual subscription rate, issues 5 and 6 £75/$110; institutional rate £160/$240; student rate £55/$80. For more information including how to subscribe, please visit the Clinical Evidence website at www.clinicalevidence.org
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Phillipa Hay (2001) studied this question.
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