Methamphetamine use and correlates in two villages of the highland ethnic Karen minority in northern Thailand: a cross sectional study

  • Eiko Kobori1Email author,

    Affiliated with

    • Surasing Visrutaratna2,

      Affiliated with

      • Yuko Maeda3,

        Affiliated with

        • Siriporn Wongchai2,

          Affiliated with

          • Akiko Kada4,

            Affiliated with

            • Masako Ono-Kihara1,

              Affiliated with

              • Yoko Hayami5 and

                Affiliated with

                • Masahiro Kihara1

                  Affiliated with

                  BMC International Health and Human Rights20099:11

                  DOI: 10.1186/1472-698X-9-11

                  Received: 19 November 2008

                  Accepted: 15 May 2009

                  Published: 15 May 2009

                  Abstract

                  Background

                  The prevalence of methamphetamine use and human immunodeficiency virus (HIV) incidence are high in lowland Thai society. Despite increasing social and cultural mixing among residents of highland and lowland Thai societies, however, little is known about methamphetamine use among ethnic minority villagers in the highlands.

                  Methods

                  A cross-sectional survey examined Karen villagers from a developed and a less-developed village on February 24 and March 26, 2003 to evaluate the prevalence and social correlates of methamphetamine use in northern Thailand. Data were collected in face-to-face interviews using a structured questionnaire.

                  Results

                  The response rate was 79.3% (n = 548). In all, 9.9% (males 17.6%, females 1.7%) of villagers reported methamphetamine use in the previous year. Methamphetamine was used mostly by males and was significantly related to primary or lower education; to ever having worked in town; to having used opium, marijuana, or heroin in the past year; and to ever having been diagnosed with a sexually transmitted infection (STI).

                  Conclusion

                  Since labor migration to towns is increasingly common among ethnic minorities, the prevention of methamphetamine use and of HIV/STI infection among methamphetamine users should be prioritized to prevent HIV in this minority population in Thailand.

                  Background

                  Historically, Thailand was once notorious for its opium production, which started in the late nineteenth century and continued until the mid twentieth century [1]. However, in modern Thailand methamphetamine is the most popular illicit drug. Of all new hospital admissions for drug treatment in Thailand in 2006, 75.6% (n = 29,235) of patients were admitted for methamphetamine use. Furthermore, 75.2% (n = 51,457) of all drug-related arrests in 2006 were methamphetamine related [2]. A household survey conducted in 2003 suggested that 0.2% of the 45 million Thai people aged 12 to 65 years had used methamphetamine during the previous year (2002), and 2.4% had used it in their lifetimes [3]. There is increasing concern that methamphetamine use is now prevalent among young people (aged 15–21 years) in Thailand. A urine test conducted among vocational school students in this age group (n = 1725) determined that 10.3% of this study group tested positive for current methamphetamine use. Additionally, 29.0% of the study group reported having ever used methamphetamine [4]. Moreover, methamphetamine use has been identified among highland ethnic minorities in areas of upper northern Thailand [5, 6].

                  In Thailand, roughly 1 million people are members of ethnic minorities, constituting 1.6% of the entire Thai population. These minorities have distinct cultural backgrounds, practices and languages. Most (approximately 920,000) are members of nine ethnic minorities that reside in the highland areas at elevations from 500 to 2,500 meters. These highlanders are officially classified as "hill tribes," or highland ethnic minorities, among which the Karen account for the largest population (47.5%) [7, 8]. Karen villagers originally resided in Myanmar for centuries but began to migrate into Thailand in the eighteenth century; today the vast majority of Karens, some 4 million, still remain in Myanmar [9]. While they face a struggle to attain their basic human rights, including democracy, and self-determination, the Karen in Thailand also face cultural and political discrimination. There is a stereotyped public view that highland ethnic minorities, including Karen residents, practice forest destruction by engaging in swidden cultivation, despite the fact that much of the deforestation has been caused by illegal logging [10]. Although the Karen have been mobile for many centuries, migration to lowland cities in search of labor or educational opportunities has increased in recent years. This was especially true in the 1980s for Karen youth. The increasing migration, together with improved infrastructure and media access in the remote villages, has resulted in a rise in material possessions that represent an elevation to prestigious cultural status as well as significant changes in lifestyle, sexual morality, and sexual behaviors [11].

                  Although opium is traditionally cultivated and used among some highland ethnic minorities, methamphetamine was first used in the highland communities in around 1996 [6]. Methamphetamine use was thought to be more common among Thais than among highland ethnic minorities, as reflected in the results of a recent survey of people attending a drug treatment center in northern Thailand [5]. Apart from its direct toxicity, methamphetamine represents a serious health concern in the context of the HIV epidemic. This is because methamphetamine use leads to engagement in other illicit drug use [12, 13], sexual initiation or increase in sexual activity [14, 15], multiple steady male partners [15], and STIs [12], though the factors associated with methamphetamine use vary depending on the study population. However, little is known about recent methamphetamine use among ethnic minority villagers in the highlands, where a rapid cultural shift is leading to increased social and cultural mixing with lowland Thai societies, in which the prevalence of methamphetamine use and HIV are high.

                  In 2003, we conducted a cross-sectional survey in two Karen villages, located in a mountainous area and with differing levels of development, to study the prevalence and social correlates of sexual behaviors, including drug use [16]. In this article, we reanalyze the data, focusing on the demographic and behavioral characteristics of methamphetamine users and the correlates of methamphetamine use.

                  Methods

                  The method used in the study is described elsewhere [16]. Briefly, we conducted a survey in two Karen villages at different levels of infrastructural development in a mountainous region in northern Thailand. The two villages were selected from villages in Category 1, the most developed level, and Category 3, a less developed level, based on the government categorization; among five possible levels within that categorization, more than 90% of villages in the study districts are classified in categories 1 to 3 [7]. We recruited all 15- to 54-year-old residents for the study, assuming that the differences between villages might reflect changes in culture and consequently in the behavioral patterns of the villagers. In detail, village A had electricity and a paved road linking it to town, enabling convenient year-round access to information and town life, whereas village B had no such infrastructure, limiting the villagers' access to town, especially in the rainy season.

                  Data were collected on February 24 and March 26, 2003. Six Karen health workers, three for each village, conducted face-to-face interviews at the respondents' homes in each village using a structured questionnaire. The questionnaire was developed based on results of eight focus group interviews with male and female Karen villagers. The questionnaire, written in Thai, was translated into the local languages through discussions among interviewers. For sensitive questions, such as questions about drug-related and sexual attitudes or behaviors, a separate answer sheet was prepared, and illustrations were used for those who were illiterate. Prior to the data-collection phase, we pretested the questionnaire in other villages that were distant from the study villages, and then revised the questions iteratively as needed. Informed consent was obtained and no names or other identifiers were collected. After completing each interview, the consent form, questionnaire, and answer sheet were put in an envelope and sealed in front of the respondent.

                  For statistical analysis, the chi-square test and Fisher's exact test when necessary were used for bivariate analysis, and a multiple logistic regression analysis was used to identify variables independently associated with methamphetamine use by entering all of the variables simultaneously. P < 0.05 was used as the critical value to determine statistical significance. In both the bivariate and multivariable analyses, the data for males and females and the data for methamphetamine non-users (users of opium, marijuana, or heroin only) and drug non-users were combined due to the small number of females and methamphetamine non-users; this actually had a limited influence on the characteristics of the combined population. The variable "graduated from a school in town" was excluded from the multivariable analysis, since it was strongly (r > 0.7) correlated with another variable, education. Variables such as age, religion, education, and main occupation were transformed into dichotomous variables for the bivariate and multivariable analyses.

                  The study protocol was approved by the National Research Council of Thailand and by the Kyoto University Graduate School and Faculty of Medicine Ethics Committee.

                  Results

                  Out of the 691 15- to 54-year-old residents of both villages, those who were not seen for three home visits or who were missing essential data on methamphetamine use, sex, age, or sexual behaviors were excluded from the analysis. This resulted in a total response rate of 79.3% (n = 548), 80.7% in village A and 76.8% in village B. None of residents visited by interviewers refused to answer the questionnaire.

                  Table 1 shows the situation of drug use among participants, of whom 9.9% (male 17.6%, female 1.7%) reported methamphetamine use in the past year and 13.3% (male 22.6%, female 3.5%) reported the use of at least one of four major drugs. In both villages, the drug users were predominantly male and methamphetamine was the most commonly used drug; only one participant reported injection drug use. Of the drug users, 61.0% and 36.4% of male users in Villages A and B, respectively, were multiple drug users, whereas all of the female users were single drug users.
                  Table 1

                  Drug use among Karen villagers in the past one yeara

                   

                  Village A

                  Village B

                    

                  Drug use

                  Male

                  (n = 174)

                  Female

                  (n = 182)

                  Total

                  (n = 356)

                  Male

                  (n = 100)

                  Female

                  (n = 92)

                  Total

                  (n = 192)

                  Grand total

                  (n = 548)

                   

                  n

                  %

                  n

                  %

                  n

                  %

                  n

                  %

                  n

                  %

                  n

                  %

                  n

                  %

                  Methamphetamine usec

                  34

                  19.5

                  5

                  2.7

                  39

                  11.0

                  15

                  15.0

                  0

                  0.0

                  15

                  7.8

                  54

                  9.9

                  Opium usec

                  16

                  9.2

                  2

                  1.1

                  18

                  5.1

                  11

                  11.0

                  3

                  3.3

                  14

                  7.3

                  32

                  5.8

                  Marijuana usec

                  18

                  10.3

                  0

                  0.0

                  18

                  5.1

                  3

                  3.0

                  0

                  0.0

                  3

                  1.6

                  21

                  3.8

                  Heroin usec

                  11

                  6.3

                  0

                  0.0

                  11

                  3.1

                  2

                  2.0

                  0

                  0.0

                  2

                  1.0

                  13

                  2.4

                  Any of 4 drugsb use

                  41

                  23.6

                  7

                  3.8

                  48

                  13.5

                  22

                  22.0

                  3

                  3.3

                  25

                  13.0

                  73

                  13.3

                  Methamphetamine non-used

                  7

                  4.0

                  2

                  1.1

                  9

                  2.5

                  7

                  7.0

                  3

                  3.3

                  10

                  5.2

                  19

                  3.5

                  Non-drug use

                  130

                  74.7

                  174

                  95.6

                  304

                  85.4

                  74

                  74.0

                  88

                  95.7

                  162

                  84.4

                  466

                  85.0

                     Missing data

                  3

                  1.7

                  1

                  0.5

                  4

                  1.1

                  4

                  4.0

                  1

                  1.1

                  5

                  2.6

                  9

                  1.6

                  Drug injection

                  0

                  0.0

                  0

                  0.0

                  0

                  0.0

                  1

                  1.0

                  0

                  0.0

                  1

                  0.5

                  1

                  0.2

                  aProportion of missing data varied from 0.5 to 6.7%

                  bMethamphetamine, opium, marijuana, or heroin

                  cIncluded multiple use

                  dIncluded multiple use except for methamphetamine

                  Table 2 describes the characteristics of the villagers according to methamphetamine use in the past year. Demographic characteristics such as age, marital status, religion, education, and graduation from a school in town were similar in both the methamphetamine users and methamphetamine/drug non-users. Methamphetamine users were more likely to be daily wage laborers, to have ever worked in town, to have used other drugs in the past year, to have ever been diagnosed with STIs in their lifetimes compared to those who were methamphetamine/drug non-users.
                  Table 2

                  Characteristics of villagers by status of drug use in the past one yeara

                    

                  Methamphetamine user

                  Methamphetamine/drug non-userb

                  Variables

                  Village A

                  (n = 39)

                  Village B

                  (n = 15)

                  Total

                  (n = 54)

                  Village A

                  (n = 317)

                  Village B

                  (n = 177)

                  Total

                  (n = 494)

                    

                  n

                  (%)

                  n

                  (%)

                  n

                  (%)

                  n

                  (%)

                  n

                  (%)

                  n

                  (%)

                  Age group (years)

                  15 – 24

                  18

                  46.2

                  2

                  13.3

                  20

                  37.0

                  141

                  44.5

                  66

                  37.3

                  207

                  41.9

                   

                  25 – 34

                  11

                  28.2

                  3

                  20.0

                  14

                  25.9

                  85

                  26.8

                  58

                  32.8

                  143

                  28.9

                   

                  35 – 44

                  5

                  12.8

                  7

                  46.7

                  12

                  22.2

                  73

                  23.0

                  37

                  20.9

                  110

                  22.3

                   

                  45 – 54

                  5

                  12.8

                  3

                  20.0

                  8

                  14.8

                  18

                  5.7

                  16

                  9.0

                  34

                  6.9

                  Sex

                  Male

                  34

                  87.2

                  15

                  100.0

                  49

                  90.7

                  140

                  44.2

                  85

                  48.0

                  225

                  45.5

                   

                  Female

                  5

                  12.8

                  0

                  0.0

                  5

                  9.3

                  177

                  55.8

                  92

                  52.0

                  269

                  54.5

                  Marital status

                  Never married

                  17

                  43.6

                  1

                  6.7

                  18

                  33.3

                  107

                  33.8

                  57

                  32.2

                  164

                  33.2

                  Religion

                  Christianity

                  15

                  38.5

                  13

                  86.7

                  28

                  51.9

                  73

                  23.0

                  144

                  81.4

                  217

                  43.9

                   

                  Animism

                  3

                  7.7

                  2

                  13.3

                  5

                  9.3

                  22

                  6.9

                  9

                  5.1

                  31

                  6.3

                   

                  Buddhism

                  20

                  51.3

                  0

                  0.0

                  20

                  37.0

                  211

                  66.6

                  22

                  12.4

                  233

                  47.2

                   

                     Missing data

                  1

                  2.6

                  0

                  0.0

                  1

                  1.9

                  11

                  3.5

                  2

                  1.1

                  13

                  2.6

                  Education

                  Primary or lower

                  25

                  64.1

                  15

                  100.0

                  40

                  74.1

                  188

                  59.3

                  135

                  76.3

                  323

                  65.4

                   

                  Junior high school

                  7

                  17.9

                  0

                  0.0

                  7

                  13.0

                  73

                  23.0

                  21

                  11.9

                  94

                  19.0

                   

                  High school or higher

                  6

                  15.4

                  0

                  0.0

                  6

                  11.1

                  52

                  16.4

                  20

                  11.3

                  72

                  14.6

                   

                     Missing data

                  1

                  2.6

                  0

                  0.0

                  1

                  1.9

                  4

                  1.3

                  1

                  0.6

                  5

                  1.0

                  Main occupation

                  Farmer

                  20

                  51.3

                  15

                  100.0

                  35

                  64.8

                  215

                  67.8

                  145

                  81.9

                  360

                  72.9

                   

                  Daily wage laborer

                  14

                  35.9

                  0

                  0.0

                  14

                  25.9

                  26

                  8.2

                  10

                  5.6

                  36

                  7.3

                   

                  Student

                  0

                  0.0

                  0

                  0.0

                  0

                  0.0

                  41

                  12.9

                  20

                  11.3

                  61

                  12.3

                   

                  Other

                  4

                  10.3

                  0

                  0.0

                  4

                  7.4

                  28

                  8.8

                  1

                  0.6

                  29

                  5.9

                   

                     Missing data

                  1

                  2.6

                  0

                  0.0

                  1

                  1.9

                  7

                  2.2

                  1

                  0.6

                  8

                  1.6

                  Graduated from a school in town

                  Graduated

                  9

                  23.1

                  0

                  0.0

                  9

                  16.7

                  82

                  25.9

                  36

                  20.3

                  118

                  23.9

                   

                     Missing data

                  1

                  2.6

                  0

                  0.0

                  1

                  1.9

                  15

                  4.7

                  3

                  1.7

                  18

                  3.6

                  Ever worked in town

                  Ever worked

                  16

                  41.0

                  10

                  66.7

                  26

                  48.1

                  50

                  15.8

                  47

                  26.6

                  97

                  19.6

                   

                     Missing data

                  0

                  0.0

                  0

                  0.0

                  0

                  0.0

                  11

                  3.5

                  1

                  0.6

                  12

                  2.4

                  Opium use

                  Yes

                  11

                  28.2

                  6

                  40.0

                  17

                  31.5

                  7

                  2.2

                  8

                  4.5

                  15

                  3.0

                   

                     Missing data

                  0

                  0.0

                  0

                  0.0

                  0

                  0.0

                  1

                  0.3

                  1

                  0.6

                  2

                  0.4

                  Marijuana use

                  Yes

                  15

                  38.5

                  0

                  0.0

                  15

                  27.8

                  3

                  0.9

                  3

                  1.7

                  6

                  1.2

                   

                     Missing data

                  0

                  0.0

                  1

                  6.7

                  1

                  1.9

                  4

                  1.3

                  3

                  1.7

                  7

                  1.4

                  Heroin use

                  Yes

                  9

                  23.1

                  0

                  0.0

                  9

                  16.7

                  2

                  0.6

                  2

                  1.1

                  4

                  0.8

                   

                     Missing data

                  0

                  0.0

                  1

                  6.7

                  1

                  1.9

                  1

                  0.3

                  5

                  2.8

                  6

                  1.2

                  Opium, Marijuana, or Herion use

                  Yes

                  23

                  59.0

                  6

                  40.0

                  29

                  53.7

                  9

                  2.8

                  10

                  5.6

                  19

                  3.8

                   

                     Missing data

                  0

                  0.0

                  0

                  0.0

                  0

                  0.0

                  4

                  1.3

                  5

                  2.8

                  9

                  1.8

                  Ever diagnosed with STIs

                  Yes

                  5

                  12.8

                  1

                  6.7

                  6

                  11.1

                  3

                  0.9

                  3

                  1.7

                  6

                  1.2

                   

                  No (Ever had sex)

                  21

                  53.8

                  12

                  80.0

                  33

                  61.1

                  210

                  66.2

                  114

                  64.4

                  324

                  65.6

                   

                  No (Never had sex)

                  13

                  33.3

                  1

                  6.7

                  14

                  25.9

                  103

                  32.5

                  54

                  30.5

                  157

                  31.8

                   

                     Missing data

                  0

                  0.0

                  1

                  6.7

                  1

                  1.9

                  1

                  0.3

                  6

                  3.4

                  7

                  1.4

                  aN = 548, Those who missed the answer on methamphetamine use were excluded

                  bIncluding methamphetamine non-user and drug non-user

                  Among methamphetamine users, those from village A (developed) were more likely to be younger, to never have been married, to be daily wage laborers, to have graduated from a school in town, to have never worked in town, to have used marijuana and heroin in the past year, to have been diagnosed with an STI in their lifetimes, compared to those from Village B; no such differences were seen between villages within methamphetamine/drug non-users.

                  Table 3 shows the results of the bivariate and multivariable analyses of the Karen villagers. In the bivariate analysis, the respondents who were male; had never married; were not farmers; had worked in town; had used opium, marijuana, or heroin in the past year; and had been diagnosed with an STI were significantly more likely to be methamphetamine users. The multivariable analysis showed that respondents who were male; had primary or lower education; had worked in town; were opium, marijuana, or heroin users in the past year; and had ever been diagnosed with an STI were significantly more likely to be methamphetamine users.
                  Table 3

                  Correlates of Methamphetamine use in the past one year among Karen villagers

                     

                  MAa user

                  Bivariate analyses

                  Multivariable analyses

                  Variables

                  N

                  n

                  %

                  P-value

                  OR

                  95CI

                  P-value

                  AOR

                  95CI

                  Village

                  A (developed)

                  356

                  39

                  11.0

                  0.239

                  1.45

                  (0.78 – 2.71)

                  0.109

                  2.20

                  (0.84 – 5.78)

                   

                  B (traditional)

                  192

                  15

                  7.8

                   

                  1.00

                      

                  Age group (years)

                  15 – 34

                  384

                  34

                  8.9

                  0.229

                  0.70

                  (0.39 – 1.26)

                  0.440

                  1.46

                  (0.56 – 3.82)

                   

                  35 – 54

                  164

                  20

                  12.2

                   

                  1.00

                      

                  Sex

                  Male

                  274

                  49

                  17.9

                  0.000

                  11.72

                  (4.59 – 29.91)

                  0.012

                  3.90

                  (1.35 – 11.28)

                   

                  Female

                  274

                  5

                  1.8

                   

                  1.00

                      

                  Marital status

                  Never married

                  182

                  18

                  9.9

                  0.984

                  1.01

                  (0.55 – 1.83)

                  0.275

                  2.90

                  (0.43 – 19.68)

                   

                  Ever married

                  366

                  36

                  9.8

                   

                  1.00

                      

                  Religion

                  Christian

                  245

                  28

                  11.4

                  0.285

                  1.36

                  (0.77 – 2.41)

                  0.893

                  1.06

                  (0.44 – 2.56)

                   

                  Buddhism or Animism

                  289

                  25

                  8.7

                   

                  1.00

                      

                  Education

                  Primary or lower

                  363

                  40

                  11.0

                  0.166

                  1.58

                  (0.82 – 3.04)

                  0.038

                  3.10

                  (1.06 – 9.03)

                   

                  Junior high school or higher

                  179

                  13

                  7.3

                   

                  1.00

                      

                  Main occupation

                  Other than Farmerc

                  144

                  18

                  12.5

                  0.209

                  1.47

                  (0.80 – 2.69)

                  0.400

                  1.52

                  (0.58 – 4.01)

                   

                  Farmer

                  395

                  35

                  8.9

                   

                  1.00

                      

                  Graduated from a school in town

                  Not graduated

                  Graduated

                  402

                  127

                  44

                  9

                  10.9

                  7.1

                  0.207

                  1.61

                  1.00

                  (0.76 – 3.40)

                    

                  -

                  Ever worked in town

                  Ever worked

                  123

                  26

                  21.1

                  0.000

                  3.69

                  (2.07 – 6.57)

                  0.003

                  3.55

                  (1.53 – 8.28)

                   

                  Never worked

                  413

                  28

                  6.8

                   

                  1.00

                      

                  Opium, Marijuana or Heroin use

                  Yes

                  48

                  29

                  60.4

                  0.000b

                  28.45

                  (14.06 – 57.56)

                  0.000

                  19.63

                  (8.04 – 47.94)

                   

                  No

                  491

                  25

                  5.1

                   

                  1.00

                      

                  Ever diagnosed with STIs

                  Yes

                  12

                  6

                  50.0

                  0.000

                  11.21

                  (3.19 – 39.41)

                  0.008

                  20.76

                  (2.18 – 197.43)

                   

                  No (Ever had sex)

                  357

                  33

                  9.2

                  0.690

                  1.14

                  (0.59 – 2.20)

                  0.238

                  2.95

                  (0.49 – 17.88)

                   

                  No (Never had sex)

                  171

                  14

                  8.2

                   

                  1.00

                      

                  aMethamphetamine

                  bFisher's exact test

                  cDaily wage worker (n = 50), student (n = 61), jobless (n = 26), housework (n = 6), other job (n = 1)

                  Discussion

                  To our knowledge, this is the first study to describe the prevalence of methamphetamine use and its correlates among the Karen villagers in a mountainous area of northern Thailand. Specifically, our study revealed that in 2003 methamphetamine was readily available and was used by 9.9% of the residents of two separate Karen villages. This is a much higher rate than that reported for the general Thai population (2.4% in 2001, and 0.2% in 2003 [3]), contrary to what has been suggested in previous reports. The results presented herein strongly suggest that methamphetamine use may have spread within the Karen population since its introduction in the mid 1990s.

                  In contrast to our hypothesis that residential development would significantly affect the drug-use behavior patterns of the local villagers, the results of the multivariable analysis showed that experience of working in town (rather than the level of development of one's village) was the significant predictor of methamphetamine use. Contact with lowland Thai society through labor migration might have increased the use of methamphetamine because it enables laborers to work longer hours or to cope with work-related stress associated with different socio-cultural situations. It is also possible that once exposed to methamphetamine, Karen villagers might be less reluctant than Thais to use new narcotic drugs, including methamphetamine, owing to the Karen's cultural and traditional use of opium, dating from the late nineteenth century [17]. The fact that the use of opium, marijuana, or heroin was a very strong predictor of methamphetamine use supports this inference. Importantly, the multivariable analysis showed that a history of an STI was potently associated with methamphetamine use, suggesting that methamphetamine users constitute an important subpopulation of Karen villagers that should be targeted by HIV-prevention programs.

                  There are some limitations to our study. There may have been interviewer or reporting bias despite the intensive training of the interviewers before data collection and the use of a separate answer sheet, with illustrations for those who were illiterate, for responding to sensitive questions. The small number of methamphetamine users (n = 54) may make the model unstable and reduce the statistical power. We may not be able to generalize the results to the entire Karen population, since the results were for only two villages. Furthermore, our results may have been influenced by the so-called "war on drugs" that the Thai government started to crack down on drug businesses in February, 2003, the month our study started; however, this influence may have been mixed, since one study identified a reduction in methamphetamine use among middle school students after the "war" began [18], while another study observed a shift to methamphetamine use from injected drugs among injection-drug users [19].

                  Conclusion

                  Despite these limitations, our study identified a high prevalence of methamphetamine use among highland Karen villagers and a strong association with experience of working in town. Since labor migration to town is increasingly common among ethnic minorities in Thailand, with the hope of achieving better economic status, the prevention of methamphetamine use and of HIV/STI infection among methamphetamine users should be given priority among minority populations in Thailand.

                  Declarations

                  Acknowledgements

                  We thank all the Karen respondents, interviewers, and staff at health centers of the Chiang Mai Provincial Health Office for their cooperation. This study was supported by a research grant from the Japanese Association for Sex Education.

                  Authors’ Affiliations

                  (1)
                  Department of Global Health and Socio-Epidemiology, Kyoto University School of Public Health
                  (2)
                  Chiang Mai Provincial Health Office
                  (3)
                  School of Human Health Science, Kyoto University Graduate School of Medicine
                  (4)
                  Department of Clinical Research and Development, National Cardiovascular Center
                  (5)
                  Center for Southeast Asian Studies, Kyoto University

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                  20. Pre-publication history

                    1. The pre-publication history for this paper can be accessed here:http://​www.​biomedcentral.​com/​1472-698X/​9/​11/​prepub

                  Copyright

                  © Kobori et al. 2009

                  This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​2.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.