Procedures for Comparison of Two Means in Independent Groups with R

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Doing a systematic review in health sciences / La revisión sistemática en las ciencias de la salud

This paper aims to provide a practical, summarized, and clear guide of steps to carry out a systematic review and is aimed at researchers in the field of Health Sciences. The review process runs from the initial questioning to the final report, providing useful information on tools available at each stage. Systematic review and meta-analysis are currently the evidence synthesis tools of the highest level of scientific quality. They are in themselves a secondary research methodology, whose objective is to locate, evaluate, and synthesize the best evidence by selecting original papers or quality primary publications. The procedure to achieve the objective is presented as a sequential and systematized process, in stages, following the transparency principle, so as to ensure its replicability

Este trabajo pretende proporcionar una guía práctica, resumida y clara de los pasos para llevar a cabo una revisión sistemática y está dirigido a los investigadores del ámbito de las ciencias de la salud. El proceso de revisión se desarrolla desde el planteamiento inicial de la pregunta hasta la elaboración del informe final, proporcionando información útil sobre herramientas disponibles en cada etapa. La revisión sistemática y el metaanálisis son actualmente las herramientas de síntesis de evidencia de más alto nivel de calidad científica. Constituyen en sí mismas una metodología de investigación secundaria, cuyo objetivo es localizar, valorar y sintetizar la mejor evidencia seleccionando los trabajos originales o publicaciones primarias de calidad. El procedimiento para alcanzar el objetivo se plantea como un proceso secuencial y sistematizado, por etapas, siguiendo el principio de transparencia, de modo que se asegure su replicabilidad

Data mining techniques for drug use research.

Drug use motives are relevant to understand substance use amongst students. Data mining techniques present some advantages that can help to improve our understanding of drug use issue. The aim of this paper is to explore, through data mining techniques, the reasons why students use drugs. A random cluster sampling of schools was conducted in the island of Mallorca. Participants were 9300 students (52.9% girls) aged between 14 and 18 years old (M = 15.59, SD = 1.17). They answered an anonymous questionnaire about the frequency and type of drug used, as well as the motives. Five classifiers techniques are compared; all of them have much better performance (% of correct classifications) than the simplest classifier (more repeated category: drug use/never drug use) in all the compared drugs (alcohol, tobacco, cannabis, cocaine). Nevertheless, alcohol and tobacco have the lower percentage of correct classifications concerning the drug use motives, whereas these use motives have better classification performance when predicts cannabis and cocaine use. When we analyse the specific motives that better predicts the category classification (drug use/never drug use), the following reasons are highlighted in all of them: "pleasant activity" (most frequent among drug users), and "friends consume" and "addiction" (both of them most frequent among never drug users). These results relate to the social dimension of drug use and agree with the statement that environmental context influences adolescent's involvement in risk behaviours. Implications of these results are discussed.

Perfilando los consumidores de cannabis que autocultivan a pequeña escala / Profiling small scale domestic grower cannabis users

El cannabis es la sustancia ilícita más consumida a nivel mundial, con una prevalencia estimada entre el 2.8 y el 5.0% de la población adulta. El auge del consumo de cannabis ha llevado a un aumento en el cultivo para el propio consumo. Como consecuencia, nos planteamos un estudio de campo con el objetivo de contrastar si consumidores con y sin autocultivo se diferencian en el perfil sociodemográfico, patrones de consumo, riesgo de consumo problemático, dependencia, y síntomas y trastornos asociados. Para ello, 761 consumidores de cannabis, 480 hombres y 281 mujeres, de los cuales 251 autocultivaban para su consumo (182 hombres y 69 mujeres), con edades comprendidas entre los 18 y 60 años (M = 26.36, DT = 5.68), respondieron a un cuestionario sociodemográfico y de patrones de consumo, a escalas de medida del consumo problemático de cannabis, dependencia del cannabis, abuso del cannabis, y de dependencia de la nicotina y del alcohol. Los resultados mostraron que el autocultivo es característico mayoritariamente de los varones, con bajo nivel académico y laboralmente activos. Asimismo, la práctica del autocultivo se relaciona con un mayor consumo de cannabis, una mayor implicación en la venta ilegal del producto, policonsumo y con problemáticas psicosociales derivadas de dicho consumo. Adicionalmente, los que autocultivan informan de mayores niveles de dependencia y de riesgo de consumo problemático de cannabis. Se discuten las implicaciones para la prevención y tratamiento de los trastornos por consumo de cannabis

Cannabis is the most widely used worldwide drug with prevalence between 2.8 and 5.0% of the adult population. Increasing use of cannabis has carried out to an escalation in home growing for selfconsumption. As a consequence, a field study to contrast if the domestic cannabis growers exhibited a different sociodemographic profile, a consumption pattern, a problematic use risk, dependence level, as well as on the clinical symptoms and related disorders, was designed. As for this, 761 cannabis users, 480 males and 281 females, of whom 251 were homegrowers for personal use (182 males and 69 females), with ages ranging from 18 to 60 years (M = 26.36, SD = 5.68), answered to a sociodemohgraphic and consumption pattern questionnaire, and to cannabis problematic use, cannabis dependence, cannabis abuse, and nicotine and alcohol dependence scales. The results showed that homegrowers are mostly males, with low academic training and working. Moreover, homegrowers have a higher cannabis consumption rates, are more implied in cannabis selling, polysubstance use, and with more psychosocial problem driven from cannabis use. Finally, homegrowers inform of higher problematic cannabis use and a higher level of cannabis dependence. The implications of the results for prevention police, and treatment of the cannabis use disorder are discussed

Cuando falle la media, utilice un M-estimador / When the mean fails, use an M-estimator

En el campo de las adicciones en muchas ocasiones se tiene que trabajar con variables cuantitativas, siendo la media aritmética el índice de localización utilizado mayoritariamente. No obstante, el uso de este índice debería limitarse a aquellas situaciones en las que las distribuciones de las variables sean simétricas. El objetivo de este trabajo es ejemplificar la importancia de recurrir a estadísticos descriptivos adecuados para resumir variables cuantitativas, mediante el estudio de la cantidad de consumo de sustancias adictivas en la adolescencia. La muestra está formada por 9300 estudiantes con edades entre los 14 y los 18 años (47.1% chicos y 52.9% chicas) que contestaron de forma anónima un cuestionario sobre consumo de sustancias. Se describe la cantidad de consumo semanal de diferentes sustancias mediante índices de localización clásicos y pertenecientes al Análisis Exploratorio de Datos (EDA). Se puede observar cómo los resultados varían notablemente en función del estadístico elegido, siendo el M-estimador de Huber un índice con valores más "reales". La media aritmética no es un buen índice para acercarnos debidamente a la realidad del consumo de drogas cuando las distribuciones son asimétricas, siendo necesario utilizar índices resistentes, tal como, entre otros, el M-estimador de Huber (AU)

In the field of addictions on many occasions one has to work with quantitative variables, and the arithmetic mean is the most used location index. Nevertheless, the use of this index should be limited to those situations in which the distributions of the variables are symmetrical. The aim of this work is to exemplify the importance of recurring to adequate descriptive statistics in order to summarize quantitative variables, through the study of the quantity of consumption of addictive substances in adolescence. The sample is made up of 9300 students between 14 and 18 years (47.1% boys and 52.9% girls) who anonymously answered a questionnaire on consumption of substances. The quantity of weekly consumption of different substances is described using classical location indexes belonging to Exploratory Data Analysis (EDA). It can be seen how the results vary noticeably according to the statistics selected, with the Huber M-estimator as the index giving more "real" values. The arithmetic mean is not a good index in order to duly approach the reality of drug consumption when the distributions are asymmetrical, in which cases it becomes necessary to use resistant indexes such as, among others, Huber’s M-estimator (AU)

Quantification of the influence of friends and antisocial behaviour in adolescent consumption of cannabis using the ZINB model and data mining.

Cannabis is the most consumed illegal drug in Europe and its repercussions are more important when taken up at an early age. The aim of this study is to analyse and quantify the predictive value of different personal, family and environmental variables on the consumption of cannabis in adolescence. The sample is made up of 9284 adolescents (47.1% boys and 52.9% girls) with an average age of 15.59 years (SE=1.17). The ZINB model highlights, as factors that increase the number of joints consumed per week, consumption by the peer group, nights out during the week, gender, the production of forbidden behaviour and the use of other substances, whereas the risk factors for the consumption of cannabis are consumption by friends, ease of access, production of forbidden behaviour and the use of other substances. Association rules highlight the relationship between cannabis consumption, ease of access, production of forbidden behaviour and tobacco consumption. Finally, decision trees enable us to predict cannabis consumption as well as the number of joints an adolescent will consume per week based on the production of forbidden behaviour, consumption of other substances and number of friends who consume cannabis. The results of this work have practical implications concerning the prevention of cannabis consumption in an adolescent population.

The influence of personal networks on the use and abuse of alcohol and drugs.

Party networks of young people are very important for socialization, but can also influence their involvement in risk behaviours or they can be protective. The influence of nightlife network of friends in using alcohol/ drugs is investigated through a survey. We explore the individual-centred networks (7.360 friends) of 1.363 recreational nightlife users in 9 European cities in 2006, through 22 friend characteristics. Statistical analysis utilised factorial analysis with varimax rotation and analysis of variance. The 69% of the sample had been drunk during the last month and more than half of them had used illicit drugs. Most of the respondents use to have a stable group of friends with whom to go out. Networks main characteristics were being more or less deviant and/or prosocial. Having not network or a less prosocial network is related to be low consumers. Having a non deviant, but prosocial network is related to being a person who gets drunk without using illegal drugs. Users of illegal drugs have a deviant and prosocial network. Finally ex users have less deviant networks, but at the same time a helper and prosocial network. Males drug use patterns appear to be less affected by the characteristics of their networks. Some preventive consequences coming from these results are already known as the importance of having less deviant friends. But some other issues are less known: to enhance certain prosocial skills may have counter preventive effects among recreational users and to influence the network for preventative purposes may be more effective among females.

La influencia de las redes personales en el uso y abuso de alcohol y drogas / The influence of personal networks on the use and abuse of alcohol and drugs

Las redes de amigos cuando se sale las noches de los fines de semana son muy importantes para la socialización, pero también pueden influir en facilitar o no el uso y abuso de alcohol y drogas ilegales. Se encuesta a 1.363 jóvenes de 9 ciudades Europeas para conocer su red de amigos (7.360) a partir de 22 posibles características. Para el análisis estadístico se utilizó el análisis factorial con rotación varimax y análisis de la varianza. El 69% de la muestra se había emborrachado durante el último mes y más de la mitad de ellos habían consumido drogas ilegales. La mayoría de los encuestados tiene un grupo estable de amigos con los que suele salir. Las principales características que definen la red de amigos es que sea más o menos desviada y/o prosocial. No tener red o ser ésta menos prosocial se relaciona con consumidores bajos. Tener una red no desviante y pro-social, se relaciona con ser una persona que se embriaga sin usar drogas o ser un ex -usuario. Los usuarios de drogas ilegales tienen una red desviada y prosocial. Las pautas de consumo de los varones parecen estar menos afectadas por su tipo de red social. Hay cuestiones preventivas ya conocidas que se desprender de los resultados, como puede ser la influencia negativa ejercida por las redes de amigos desviantes. Sin embargo, no se conoce tanto el efecto, también negativo, de tener redes más prosociales. Mejorar las capacidades prosociales puede tener, por tanto, efectos contra preventivos. Por otro lado, puede que influir sobre la red de amigos tenga mayores efectos preventivos entre las mujeres (AU)

Party networks of young people are very important for socialization, but can also influence their involvement in risk behaviours or they can be protective. The influence of nightlife network of friends in using alcohol/drugs is investigated through a survey. We explore the individual-centred networks (7.360 friends) of 1.363 recreational nightlife users in 9 Europe ancities in 2006, through 22 friend characteristics. Statistical analysis utilised factorial analysis with varimax rotation and analysis of variance. The 69% of the sample had been drunk during the last month and more than half of them had used illicit drugs. Most of the respondents use to have a stable group of friends with whom to go out. Network’s main characteristics were being more or less deviant and/or prosocial. Having not network or a less prosocial network is related to be low consumers. Having a non deviant, but prosocial network is related to being a person who gets drunk without using illegal drugs. Users of illegal drugs have a deviant and prosocial network. Finally ex users have less deviant networks, but at the same time a helper and prosocial network. Males drug use patterns appear to be less affected by the characteristics of their networks. Some preventive consequences coming from these results are already known as the importance of having less deviant friends. But some other issues are less known: to enhance certain prosocial skills may have counter preventive effects among recreational users and to influence the network for preventative purposes may be more effective among females (AU)

Occupational safety and health in Spain.

Occupational Health and Safety in Spain has improved considerably over the last decade, most likely due to a new concept where an overall concept of safety culture is defined. Important changes in industrial safety, hygiene, and psychosocial factors present an optimistic panorama for the future of Spain. Despite this general improvement, according to the European Convergence Program, Spanish statistics still offer far from good safety results. In fact, according to 1997 official statistics, Spain had the highest incidence rate for nonfatal occupational accidents of all European Union (EU) countries, and occupied third place for fatal accidents. This paper summarizes the organizational structure of the Spanish National System of Health & Safety at Work, its effective health and safety laws, and statistics on the Spanish work environment obtained from III Spanish National Survey on Work Conditions (1997). The researchers hope that the findings of this work will have an impact on Spanish industry that will subsequently bring about improvements in work conditions and develop assessment and intervention models in occupational health and safety, from a theoretical position integrating environmental, human, and organizational factors.