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United States has highest level of illegal cocaine and cannabis use, and more

Peer-Reviewed Publication


United States has highest level of illegal cocaine and cannabis use

A survey of 17 countries has found that despite its punitive drug policies the United States has the highest levels of illegal cocaine and cannabis use. The study, by Louisa Degenhardt (University of New South Wales, Sydney, Australia) and colleagues, is based on the World Health Organization's Composite International Diagnostic Interview (CIDI) and is published in this week's PLoS Medicine.

The authors found that 16.2% of people in the United States had used cocaine in their lifetime, a level much higher than any other country surveyed (the second highest level of cocaine use was in New Zealand, where 4.3% of people reported having used cocaine). Cannabis use was highest in the US (42.4%), followed by New Zealand (41.9%).

In the Americas, Europe, Japan, and New Zealand, alcohol had been used by the vast majority of survey participants, compared to smaller proportions in the Middle East, Africa, and China.

The survey found differences in both legal and illegal drug use among different socioeconomic groups. For example, males were more likely than females to have used all drug types; younger adults were more likely than older adults to have used all drugs examined; and higher income was related to drug use of all kinds. Marital status was found to be related to tobacco, cannabis, and cocaine use, but not alcohol use (the never married and previously married having higher odds of lifetime cocaine and cannabis use than the currently married; tobacco use is more likely in people who have been previously married while less likely among the never married).

Drug use "does not appear to be simply related to drug policy," say the authors, "since countries with more stringent policies towards illegal drug use did not have lower levels of such drug use than countries with more liberal policies." In the Netherlands, for example, which has more liberal policies than the US, 1.9% of people reported cocaine use and 19.8% reported cannabis use.

Data on drug use were available from 54,068 survey participants in 17 countries. The 17 countries were determined by the availability of research collaborators and on funding for the survey. Trained lay interviewers carried out face-to-face interviews (except in France where the interviews were done over the telephone) using a standardized, structured diagnostic interview for psychiatric conditions and drug use. Participants were asked if they had ever used alcohol, tobacco, cannabis, or cocaine.

The study's main limitations are that only 17 countries were surveyed, within these countries there were different rates of participation, and it is unclear whether people accurately report their drug use when interviewed. Nevertheless, the findings present comprehensive data on the patterns of drug use from national samples representing all regions of the world.

Citation: Degenhardt L, Chiu W-T, Sampson N, Kessler RC, Anthony JC, et al. (2008) Toward a global view of alcohol, tobacco, cannabis, and cocaine use: Findings from the WHO World Mental Health Surveys. PLoS Med 5(7): e141. doi:10.1371/journal.pmed.0050141.



Louisa Degenhardt
National Drug and Alcohol Research Centre
University of New South Wales
Sydney, New South Wales 2052
+61 2 9385 0230
+61 2 9385 0222 (fax)

David Cameron
Associate Director of Public Affairs
Harvard Medical School
Boston, MA 02115
United States of America
+1 671 432 0441

Delaying childbirth is associated with impaired contraction of the uterus and rising rates of cesarean section

Impaired contraction of the uterus (womb) may play a part in the association of advancing maternal age with increased cesarean rates according to a study published in PLoS Medicine this week. In a two part study, Professor Gordon Smith and colleagues (Cambridge University, UK) analyzed a large Scottish data base to characterize the association between maternal age and outcome of labor, specifically looking at what proportion of the increase in primary cesarean rates could be attributed to changes in maternal age distribution. They then went on to study samples of myometrium (muscle from the wall of the uterus) taken during routine cesarean sections to determine whether muscle contractility varied with maternal age.

Cesarean sections are associated with higher mortality and morbidity rates compared with vaginal deliveries. Rates of caesarean section have dramatically increased over the last 20-30 years throughout the developed world. This increase is a concern as it may have implications for the mother, baby, healthcare providers, and policy makers. According to the World Health Organization (WHO), the UK's cesarean rate was 20% in 2004, Canada's was 22.5% in 2001-2002 and the United States' was 30.2% in 2005 — all above the WHO's proposed acceptable rate of between 10% and 15% for countries in the developed world. Previous epidemiological studies have reported a trend of increased rates of cesarean sections with maternal age which is consistent in different countries. However, the reason for these increased rates remains unclear. Moreover, it was unclear to what extent, if any, the trend of delaying childbirth had contributed to the increased cesarean rates.

This study was carried out in two parts. First, the researchers analyzed data collected by the Scottish Morbidity Record (SMR2) from 1980 to 2005 — over 0.5m available records. A linear association between the risk of having a cesarean section and advancing maternal age in first pregnancies was found. They observed striking changes over the period of study. The proportion of women aged 30-34 increased three fold, the proportion aged 35-39 increased seven-fold and the proportion aged 40 or older increased 10-fold. Over the same period, the cesarean rate more than doubled. The researchers estimated that around 38% of the additional procedures would have been avoided if maternal age distribution had remained the same as in 1980. They therefore concluded that a substantial proportion of the increase in cesarean section rates may be due to the trend of delaying first childbirth.

Second, they hypothesized that the increased risk of caesarean section among older women is a result of a biological effect of aging on the ability of the muscle of the uterus to contract. They evaluated this hypothesis by examining biopsies from the uteruses of a separate group of 62 women (of mixed parity) undergoing routine elective cesarean delivery in Cambridge. They found that advancing age was associated with impaired uterine function as evidenced by a reduced degree of spontaneous contraction and the type of spontaneous contraction.

The analysis of Scottish data adds to the evidence that advancing maternal age is associated with higher rates of cesarean sections. Moreover, it indicates that the trend of delaying childbirth has substantially contributed to recent increases in cesarean rates. The researchers' further work at the NIHR Cambridge Biomedical Research Centre at the Rosie Hospital in Cambridge, UK suggests a possible mechanism for this association, i.e., impaired contraction of the uterus. Although further work will be needed in other populations, as the authors comment, "understanding the determinants and management of dysfunctional labor in older women is central to designing strategies for reducing population cesarean delivery rates without adversely affecting maternal and infant outcomes."

Citation: Smith GCS, Cordeaux Y, White IR, Pasupathy D, Missfelder-Lobos H, et al. (2008) The effect of delaying childbirth on primary cesarean section rates. PLoS Med 5(7): e144. doi:10.1371/journal.pmed.0050144.



Gordon C Smith
University of Cambridge
Obstetrics & Gynaecology
The Rosie Hospital
Robinson Way
Cambridge, Cambridgeshire CB2 2SW
United Kingdom
+44 12233 36871 (PA)
+44 12232 48811 (fax)


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