Social Audit Ltd
P O Box 111 London NW1 8XG
Telephone/Fax 44 (0)171 586 7771
Dr J.M. Bertolote,
Division of Mental Health
World Health Organisation/OMS,
CH-1211 GENEVA 27 Switzerland 22 October 1999

Dear Dr. Bertolote,

I am writing to you both because of your involvement in the WHO Programme on Substance Abuse, also because Dr Costa e Silva had mentioned in earlier correspondence ( that you act as the WHO liaison officer with the World Psychiatric Association (WPA). My enquiry relates to a small but I think very important point, arising from the report on Rational Use of Benzodiazepines (WHO/PSA/96.11) which, as you know, was based on the work of a WPA task force on benzodiazepines. My concern, briefly, is this:

1. At page 31, the PSA/96.11 report states that "dependence to benzodiazepines is indeed limited - about one per cent of users according to Khan (1992)"

2. There appears to be no reference to this figure of 1% in the paper cited (Khan I, International regulation of benzodiazepines, Progress in Neuro-psychopharmacology and Biological Psychiatry, 1992, 16, 9-16).

3. The statement that "benzodiazepine dependence is indeed limited" is certainly not well supported by the evidence cited at 5.2.2 of the PSA/96.11 report, nor can it readily be reconciled with the control of most benzodiazepines under Schedule IV of the 1971 UN Convention on Psychotropic Substances.

4. The estimate of about a 1% dependence rate, attributed to WHO, appears to be quite widely cited in the scientific literature, if not actively promoted by commercial interests. The clear implication is that the WHO (WPA) estimate is correct, and to be preferred to other (generally higher) estimates. See, for example: Strömstedt A., Journal of the Swedish Medical Association, 35, 1998 and at

You will appreciate the significance from this of my requesting further information about the source of the ~1% estimate. If it can not be attributed to Khan (1992), where does it come from and on what evidence was it based?

Many thanks for your attention and I look forward to hearing from you.

Yours sincerely,
Charles Medawar



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